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  • ItemEmbargo
    A comprehensive study of Salmonella infections and microbial analysis of probiotics on beef cattle
    (Colorado State University. Libraries, 2023) Thompson, Tyler Warren, author; Nair, Mahesh Narayanan, advisor; Geornaras, Ifigenia, committee member; Belk, Keith, committee member; Noyes, Noelle, committee member; Morley, Paul, committee member
    Non-typhoidal Salmonella remains a significant concern for food safety in the United States, causing millions of infections, hospitalizations, and deaths yearly. The Healthy People 2030 initiative set forth by the U.S. Department of Health and Human Services aims to address this issue by establishing goals and objectives for national health promotion and disease prevention, including two objectives focused on Salmonella control in the food supply. The recent declaration of Salmonella as an adulterant in certain poultry products by the U.S. Department of Agriculture further highlights the urgency of this issue. To align with the Healthy People 2030 goals and achieve a 25% reduction in salmonellosis, the U.S. Department of Agriculture's Food Safety and Inspection Service (FSIS) implemented new performance standards for beef products. However, such policies must be supported by quantitative microbial risk assessments (QMRA) to determine their impact on Salmonella infections. Therefore, these analyses would benefit from a systematic review examining existing literature on Salmonella, considering factors such as illness rates, exposure, and bacterial loads. This review included 42 articles that provided data necessary for fitting a dose-response model to empirical data that describes how dose, virulence group, and food vector affect illness (attack) rates. Results from the mixed-effects logistic regression model showed significant impacts of log dose consumed, virulence group, and food vector on illness rates. Notably, Salmonella serogroups of "Higher" virulence were found to be associated with greater odds of illness than "Lower" virulence strains. The study highlights the need for improved data reporting and standardized outbreak investigations to enhance the fitting of models to outbreak data. By considering factors like serovar group and food vector in the modeling process, regulators can demonstrate what influences attack rate to frame more effective food safety policies. In conclusion, this systematic review provides valuable insights into Salmonella infection risk from food sources and emphasizes the importance of evidence-based policies to reduce the burden of Salmonella-related illnesses and improve food safety in the United States. Liver abscesses in beef cattle are a common problem associated with highly-fermentable carbohydrate diets during finishing, leading to decreased production efficiency and aggregate carcass value. Dietary antimicrobial supplementation, such as tylosin, helps to control liver abscesses but raises concerns about selection for antimicrobial resistance. This study examined the impact of a probiotic mixture of propionic and lactic acid bacteria on microbial communities and antimicrobial resistance genes (ARGs) in fecal and liver abscess samples from beef cattle alongside Salmonella populations of mesenteric lymphatic tissues. Treatment diets fed in this study included a probiotic mixture alone (DFM), inclusion of Tylosin (TYL), a combination of including both (DFM+TYL), and a control group diet that did not include any supplements (CON). Fecal samples were collected at the time that feeding started, and then 28 d before arriving at the abattoir, where liver abscesses and mesenteric lymph nodes were sampled. Fecal and liver abscess samples were subjected to 16S rRNA and targeted enriched shotgun metagenomics to evaluate microbial communities and resistance genes of bacteria present. A portion of the liver abscess and mesenteric lymph nodes were tested for presence of Salmonella using PCR with further analysis of enumeration and serotype classification for mesenteric lymph nodes. Results showed no differences (P > 0.05) between the fecal microbiomes of the different treatment groups, and the addition of tylosin or probiotic mixture did not impact the fecal resistome. Similarly, no differences (P > 0.05) were observed between the liver abscess microbiomes of the different (P > 0.05) treatment groups, with Fusobacteria and Bacteroidetes being the dominant phyla in liver abscesses. Results indicated that incorporating DFMs did not affect Salmonella prevalence in the cattle's mesenteric lymph nodes or liver abscesses. Presence of Salmonella was found at low levels in only 22% of samples (91 positive out of 503 samples), just below 1 log CFU/g, and was predominantly represented by the C1 serogroup in mesenteric lymph nodes. These findings suggest that while diet interventions may not have a substantial impact, Salmonella can colonize mesenteric lymphatic tissues in cattle at low frequencies and concentrations. Treatment groups tested had no impact (P > 0.05) on fecal and liver abscesses microbiomes and resistance gene presence, along with no impact on Salmonella prevalence in liver abscesses or mesenteric lymphatic tissues.
  • ItemOpen Access
    Benchmarking and analysis of current pre-slaughter management factors and their influence on welfare and meat quality outcomes in fed beef cattle
    (Colorado State University. Libraries, 2023) Davis, Melissa, author; Edwards-Callaway, Lily, advisor; Nair, Mahesh, committee member; Hess, Ann, committee member; Mooney, Daniel, committee member
    Several factors related to pre-slaughter management of fed beef cattle and their impacts on welfare and meat quality have been identified and discussed thoroughly in previous literature. However, a full catalog of these factors and indicators used to evaluate their impacts on cattle welfare is missing. Additionally, benchmarked data for these factors and welfare and meat quality outcomes, and an analysis of their relationships on a large scale is underrepresented in current literature. The objectives of the first chapter of this dissertation were to catalog pre-slaughter management factors, identify indicators used to evaluate their impacts, and ultimately gain a further understanding of the relationships between pre-slaughter management factors and cattle welfare. This review included an in-depth analysis of 69 studies from across the globe that identified factors related to transportation and handling using behavioral and physiological indicators to measure welfare that were the most researched throughout the studies. The discussion of this review also identified pre-slaughter factors that require benchmarking and/or more research on their potential impacts on cattle welfare. Thus, the objectives of the second chapter in this dissertation was to benchmark pre-slaughter management factors at a collection of commercial fed cattle processing facilities. This data collection took place at five commercial processing facilities in the West, Midwest, and Southwest regions of the United States from March 2021 to July 2022. Data were collected on a total of n = 637 slaughter lots representing n = 87,220 head of cattle. Transportation factors such as distance travelled and the time cattle waited on the truck to unload after arriving at the facility, space allowance in lairage for cattle, lairage duration and cattle mobility was recorded. Environmental factors were later recorded from an online weather service, and cattle characteristics and several meat quality factors including bruising, quality grading, carcass weight and dark cutting were obtained from plant records. Descriptive statistics were calculated for both the lot and individual animal level depending on the variable. Cattle travelled on average, 155.8 ± 209.6 km (Mean ± SD) to the processing facility from the feedlot, waited 30.3 ± 39.7 minutes to unload at the plant and were held in lairage for 200.7 ± 195.0 minutes. The mean lairage density was 3.1 ± 2.0 m2/animal, and a majority of cattle (91.8%, n = 77,645) were scored as having normal mobility. Carcass bruising prevalence was 69.7% (n = 57,099), and of those that were bruised, 65.2% (n = 39,856) had multiple bruises. Having this baseline benchmarking data outlines not only areas that need further improvement, but also areas in this sector that the industry has already improved upon. This benchmarking data also identified the need for additional analysis on the relationships between these factors and outcomes. Therefore, the objective in the final chapter of this dissertation was to assess the effects of these factors on select welfare and meat quality outcomes in fed beef cattle. Using the same data set and methods as in the second chapter, any slaughter lots with no response variables or < 75% of predictor variables present were excluded. A total of n = 619 slaughter lots representing 84,508 head of cattle were used for further analysis. Descriptive statistics for this subset of data and linear and logistic regression models were performed to assess relationships. Statistical significance was determined at P < 0.05. Predictor variables of interest included plant, breed, sex class, operation shift at the plant, distance travelled, truck waiting time to unload, lairage duration and space allowance, THI, and wind speed. Outcome variables of interest included mobility, bruising, dark cutting, quality grades, and hot carcass weights. All outcomes of interest were associated with several pre-slaughter factors of interest, particularly plant and cattle breed. Increased odds of impaired mobility were associated with increased distance travelled (1.001, 1.000 – 1.001; OR, CI) and truck waiting time (1.003, 1.001 – 1.004; OR, CI). Increased odds of carcass bruising were associated with decreases in distance travelled (0.997, 0.996 – 0.998; OR, CI), but increases in space allowance in lairage (1.035; 1.017 – 1.053; OR, CI). Cattle that experienced increases in lairage duration were associated with decreased hot carcass weights (P < 0.0367) and increased odds of cark cutting (1.034, 1.001 – 1.068; OR, CI). Additionally, cattle that were slaughtered during the first shift of operation at the plant were associated with decreased odds of being bruised (0.806, 0.772 – 0.842; OR, CI), being classified as a dark cutter (0.416, 0.336 - 0.514; OR, CI), and having a poorer quality grade (0.777, 0.657 - 0.920; OR, CI). Results from these studies identify areas where further and more detailed research is needed to fill knowledge gaps and fully understand these relationships. This research also has the potential to aid in informed decision-making regarding cattle management during the pre-slaughter period and further educate the industry on sustainable management practices.
  • ItemOpen Access
    Developing a strategy for identifying genetically important animals
    (Colorado State University. Libraries, 2023) Wilson, Carrie S., author; Speidel, Scott, advisor; Enns, R. Mark, advisor; Lewis, Ronald, committee member; Mason, Esten, committee member
    Livestock researchers often need to sample animals within a breed to serve as a representative sample of the breed. Identifying the most relevant animals to include in research for genotyping, building a reference population, or inclusion in a gene bank is a complex issue. A suboptimal sampling strategy can lead to biased results, the need for additional sampling, and can be costly. When using public funds (e.g., federal grant or federal appropriations) or member fees (e.g., breed association funds), we have a responsibility to efficiently spend these investments in a wise manner, optimizing which animals are sampled before the research, genotyping, or gene banking begins. The first objective was to develop a sampling strategy to maximize the genetic diversity captured for the sampled animals. Simulated data is ideal for this type of study as there is no limitation to the testing parameters. The primary benefit of simulation with this research was the opportunity to have known genotypes for every animal in the population. Since genotypes will almost never be available for the entire population in the real world, and identifying animals to genotype may in fact be the purpose of the sampling, pedigree-based sampling methods were chosen. Sampling methods tested included optimal contribution selection (OCS) and the genetic conservation index (GCI). The OCS selects parents based on constraining their co-ancestry rather than minimizing inbreeding. GCI seeks to maximize the number of founders in an animal's pedigree. The sampling strategy developed in Objective 1 was used to identify a subset of 100, 50, and 25 animals from each breed and the genetic diversity captured by each sampling method was assessed using both quantitative and molecular methods. AlphaSimR was used to simulate the population for sampling. After an initial randomly mating founder population was developed, an additional 15 years of selection for phenotypic weaning weight was simulated and resulted in a fully genotyped population with 13,662 animals per year. The simulation was designed to represent a sheep population. After the sampling strategies were applied to the simulated population, they were next applied to Suffolk sheep and Simmental beef populations for further assessment of their ability to capture genetic diversity. To assess population structure based on molecular data, the Suffolk and Simmental populations were limited to genotyped animals and their ancestors. The simulated population represented a large purebred population (n=204,930) with a moderate number of markers (n=53,901). The Suffolk population represented a small population (n=1,565) with many markers (n=606,006). Lastly, the Simmental population represented a large, admixed population (n=54,790) with a moderate number of markers (n=29,449). For the second objective, the population structure of the full populations, comprised of genotyped animals, was assessed, and compared to the population structure of the animals from each sampling strategy. Each sampling strategy selected 100, 50, and 25 animals. The measure of success of capturing the genetic diversity of the population was a molecular-based measure defined by capturing the available alleles in the population. Other population structure measures included a comparison of a phenotypic trait, breeding values, inbreeding levels, heterozygosity, minor allele frequency (MAF) category classification, runs of homozygosity (ROH), Ne, and model-based population structure to visualize subpopulations. While both sampling strategies were effective at capturing the available alleles in the population, OCS was more successful than GCI when comparing the same sample size. Success of capturing alleles decreased as sample size decreased from 100 to 50 to 25. Overall, OCS with a sample of 100 animals (OCS 100) was the most successful at capturing the available alleles in the population, capturing 96.5, 99.3, and 99.9 percent of the alleles for the simulated, Suffolk, and Simmental populations, respectively. For a sampling strategy to be useful, it needs to be effective across a variety of species and breeds with a variety of breed histories and population sizes. The third objective was to compare the three populations evaluated in this research and compare the effectiveness of the sampling strategies across these populations. Population structure was compared for the three populations. Then, the effectiveness of OCS 100 was compared. The three populations differed in population size and the amount of admixture present. The simulated population was characterized by a large number of low frequency alleles (n=5,339) that proved difficult to capture. The Suffolk population was small and consisted of 14 distinct subpopulations. The Simmental population had high levels of heterozygosity and less distinct subpopulation structure. Despite disparate populations, OCS 100 was the most robust across the three populations, consistently capturing the highest percentage of available alleles compared to the other sampling strategies. In summary, OCS 100 was the most effective sampling strategy across three different populations. A low-cost pedigree-based sampling strategy can be used to capture the genetic diversity in a population. Researchers will need to weigh the risk of a greater loss of alleles when selecting a smaller population size. Risk could be further reduced by increasing the selected population size. Knowledge of the prevalence of low frequency alleles in the population and the value of capturing them should be considered.
  • ItemOpen Access
    In vivo and in vitro attributes of copper, zinc, and manganese sources in beef cattle nutrition
    (Colorado State University. Libraries, 2023) Guimaraes, Octavio, author; Engle, Terry T., advisor; Wagner, John, committee member; Geornaras, Gina, committee member; Nair, Mahesh, committee member; Holt, Tim, committee member
    Trace minerals are not just vital components in the diets of domestic livestock species; they are also essential for ensuring optimal performance, health, reproduction, and a robust immune system. In today's volatile markets, producers and nutritionists face the challenge of meeting predefined goals and targets. They must employ strategies that can maximize production and efficiency. The intricate mechanisms governing the digestion, absorption, and storage of copper (Cu), zinc (Zn), and manganese (Mn) are influenced by various factors, including diet type, breed, life stage, among many others. Research has uncovered intriguing opportunities to enhance the utilization of trace minerals (TM) in ruminant nutrition. To further our comprehension of the digestion, absorption, and retention of modern trace mineral forms, this study conducted 3 experiments aimed at investigating the in vivo and in vitro characteristics of hydroxy trace minerals (HTM), organic chelated trace minerals (CTM), and sulfate trace minerals (STM) forms of Cu, Zn, and Mn. This dissertation is the continuation of a Master Thesis submitted by Guimaraes et al., 2021. In the current series of experiments the influence of TM source on digestibility and ruminal solubility was investigated. The objectives of experiment 1 were to determine the effects of TM source on 1) nutrient digestibility and ruminal fermentation, 2) concentrations of soluble Cu, Zn, and Mn in the rumen following a pulse dose of TM, and 3) Cu, Zn, and Mn binding strength on ruminal digesta using dialysis against a chelating agent in steers fed a diet formulated to meet the requirements of a high producing dairy cow. Twelve Angus steers fitted with ruminal cannulae were adapted to a diet balanced with nutrient concentrations similar to a diet for a high producing lactating dairy cow for 21 d. Steers were then randomly assigned to dietary treatments consisting of 10 mg Cu, 40 mg Mn, and 60 mg Zn/kg DM from either sulfate (STM), hydroxychloride (HTM) or complexed trace minerals (CTM). The experimental design did not include a negative control (no supplemental Cu, Mn, or Zn) because the basal diet did not meet the NRC (Nutrient Requirement for Beef Cattle) requirement for Cu and Zn. Copper, Mn, and Zn are also generally supplemented to lactating dairy cow diets at concentrations approximating those supplied in the present study. Following a 14-d adaptation period, total fecal output was collected for 5-d. Following the fecal collection period, rumen fluid was collected for VFA parameters. On the following day, the same diet was provided for 14 d, without supplemental Cu, Zn, and Mn. This period served as a wash-out period. A pulse dose of 100, 400, and 600 mg of Cu, Zn, Mn, respectively, from either STM, HTM, or CTM, was administered via ruminal cannulae to the steers on day 15. Over a 24-h period ruminal samples were obtained every 2-h. Following centrifugation, the supernatant was analyzed for Cu, Mn, and Zn. Ruminal solid digesta samples from times 0, 12, and 24 hours after bolus dosing were exposed to dialysis against Tris-EDTA. The digestibility of NDF and ADF were lesser in STM vs. HTM and vs. CTM supplemented steers. Steers receiving HTM and CTM had greater total VFA concentrations than STM, and molar proportions of individual VFA were not affected by treatment. Ruminal soluble Cu and Zn concentrations were greater post dosing in STM and CTM supplemented steers at 2, 4, and 6 h for Cu and 4, 6, 8, 10 and 12 h for Zn when compared to HTM supplemented steers. The release of Cu and Zn from ruminal solid digesta following dialysis against Tris-EDTA at 12 and 24 h post-dosing was greater for steers receiving HTM compared to those receiving STM or CTM. Results indicate trace mineral source impacts: 1) how tightly bound Cu and Zn are to ruminal solid digesta; 2) fiber digestion; 3) and ruminal total VFA concentrations. The objective of experiment 2 was to evaluate the effects of sources of STM and HTM fed at the same levels on 1) nutrient digestibility and fermentation characteristics, 2) ruminal solubility of Cu, Zn, and Mn following a pulse dose of trace mineral I, and 3) binding strength of Cu, Zn, and Mn on ruminal solid digesta upon dialysis against a chelating agent. Minor dietary changes can have a direct impact on ruminal pH, temperature, microbial population, and redox potential, which will influence fermentation, and ultimately affect nutrient digestibility. These changes can influence or be influenced by the solubility of certain TM in the rumen. Rumen soluble TMs can alter nutrient digestibility, fermentation, and increase chances of antagonistic interaction. Twelve ruminally cannulated Angus steers (BW 587.6 ± 23.1 kg) were adapted to a diet balanced to meet requirements of finishing steers for 21 d. Steers were then randomly assigned to dietary treatments consisting of Cu, Mn, and Zn supplemented at 18, 40, and 90 mg/kg DM, respectively, from STM or HTM sources (n = 6 steers/treatment; experimental unit = steer). Following the 14 days treatment adaptation period total fecal output was collected for 5 d. Digestibility of DM, CP, Starch, NDF, and ADF was not affected (P > 0.15) by TM source. On d 6, rumen fluid was collected at 0, 2, and 4 h post feeding for VFA analysis. There were no treatment x time interactions for any VFA measured. However, HTM steers had greater (P < 0.05) ruminal molar proportions of propionate and tended (P < 0.07) to have greater molar proportions of valerate compared to STM steers. Steers fed STM had greater (P < 0.05) molar proportions of butyrate compared to HTM steers. Steers were then fed the same high concentrate diet without supplemental Cu, Zn, or Mn for 14 d. On d 15 steers received a pulse dose (via rumen cannulae) from either STM or HTM. Ruminal samples were obtained at 2 h intervals starting at -4 and ending at 24 h relative to dosing. There was a treatment x time interaction (P < 0.05) for ruminal soluble Cu concentrations. Ruminal soluble mineral concentrations were greater (P < 0.05) for Cu at 4, 6, 8, and 16 h post dosing in STM compared to HTM supplemented steers. There was no treatment x time interaction for ruminal soluble Zn or Mn concentrations. The release of Cu, Zn, and Mn from ruminal solid digesta following dialysis against Tris-EDTA at 12 and 24 h post-dosing was greater (P < 0.01) for steers receiving HTM compared to those receiving STM. Results of this experiment indicate that trace mineral source affects how tightly bound Cu, Zn, and Mn are to ruminal solid digesta, and that ruminal solubility of Cu differs between STM and HTM sources and may impact rumen fermentation characteristics. Experiment 3: This study analyzed samples from experiments investigating TM source effects on nutrient digestibility, short-chain fatty acid production, Cu, Zn, and Mn ruminal solubility, and binding strength in rumen insoluble digesta. Twelve Angus steers (5+ years old) participated in three studies: Study 1 (Guimaraes et al., 2020, 2021; medium quality forage diet), Study 2 (Guimaraes et al., 2022; dairy type diet), and Study 3 (unpublished, Chapter 3 of this dissertation; high concentrate diet). Due to impacts on digestibility, fermentation, mineral solubility, and binding in all studies, microbiome analysis was conducted to assess potential bacterial and protozoa population shifts from all studies. In Study 1 (medium quality forage diet), Papillibacter was the predominant species in the rumen. Rumen samples showed a significant time point impact on Shannon's PD (P < 0.05). Beta diversity analysis using unweighted UniFrac revealed notable differences in community diversity between rumen and fecal samples (q < 0.001). Rumen microbiota clustered at multiple time points. No beta diversity differences between STM and HTM were observed at baseline (Time A, q = 0.23), but differences emerged after adaptation (Time C, q < 0.03) and during total collection (Time F, q < 0.01). ANCOM analysis revealed higher abundance of Papillibacter, Ruminoccoccaceae, and Prevotellaceae in rumen samples, regardless of TM source. No significant differences were found in fecal samples. ANCOM analysis did not detect measurable differential abundance between trace mineral sources in fecal or rumen samples following Alpha and Beta diversity results. In Study 2 (dairy diet), Moraxellaceae was the most prevalent species within the rumen. Rumen samples showed a significant time point effect on Shannon's PD (P < 0.001), with noteworthy differences between several time points. However, TM source had no impact on Shannon's PD (P = 0.15). Fecal samples showed no differences in time points or TM sources. Beta diversity analysis using unweighted UniFrac revealed a significant distinction between microbial community diversity in rumen and fecal samples (q < 0.001). Rumen microbiota clustered differently at various time points. Trace mineral source did not affect Beta diversity, but there was a tendency toward greater diversity with HTM supplementation (q = 0.07). ANCOM analysis found higher abundance of ASVs Moraxellaceae, Planococcaceae, Ruminoccoccaceae, and Prevotellaceae in the rumen environment, regardless of TM source. No significant differential abundance was detected between TM sources in rumen samples, consistent with Shannon's PD diversity analysis. In Study 3 (high concentrate diet), Moraxellaceae and Planococcaceae were the most abundant in rumen samples. Rumen samples showed a significant impact of collection time point on Shannon’s PD (P < 0.001), with significant differences between several time points. However, TM source had no effect on Shannon’s Diversity (P = 0.19). Interestingly, Shannon’s Diversity in feces showed significant differences between TM sources (P < 0.03), with STM having lesser diversity than HTM. There was no effect of time point in fecal samples (P = 0.38). Beta diversity analysis using unweighted UniFrac revealed clear differences between microbial diversity in rumen and fecal samples (q < 0.001). ANCOM analysis found higher abundance of ASVs Moraxellaceae, Prevotellaceae, Planococcaceae, and Ruminoccoccaceae in the rumen environment, regardless of TM source. In conclusion, this study provides valuable insights into the complex interplay between TM sources, the rumen microbiome, and various aspects of rumen health and function. While TM sources did not significantly alter the rumen microbiome composition, time points demonstrated substantial effects on microbial communities. These findings contribute to our understanding of how dietary factors can influence rumen ecology and function, with potential implications for livestock nutrition and management strategies. In conclusion, while experiment 1 showed that HTM and CTM sources positively impacted fiber digestibility and ruminal VFA concentrations compared to STM, experiment 2 indicated that the diet type could influence these effects. However, ruminal soluble mineral concentrations remained greater in STM-supplemented steers. Experiment 3 further highlighted the differences in rumen and fecal microbiota diversity between TM sources. These findings underscore the importance of selecting the appropriate TM source based on specific dietary and production requirements. The interactions between TMs, diet type, and the rumen microbiome are complex and require further investigation to optimize ruminant nutrition and overall well-being. This research builds upon previous studies and contributes valuable insights into the utilization of TMs in ruminant nutrition, paving the way for more informed decision-making in livestock production practices.
  • ItemOpen Access
    Heterosis and breed percentage effects on reproductive performance and preweaning traits in a multibreed beef cattle herd in Panama
    (Colorado State University. Libraries, 2023) Gonzalez Murray, Roderick Alexander, author; Speidel, Scott E., advisor; Enns, R. Mark, advisor; Thomas, Milton G., committee member; Coleman, Stephen J., committee member; Holt, Timothy, committee member
    Panama is located in Central America and is characterized by a tropical climate. Given the tropical climate conditions, Zebu cattle (Bos indicus) are the most predominant breeds in cow–calf systems due to greater resistance to internal and external parasites, and greater tolerance to elevated ambient temperatures and humidity when compared to Bos taurus beef breeds. Zebu is a breed that is reproductively inefficient due to Age at First Calving (AFC) being over 36 months and having longer calving intervals (CI), ranging between 12.2 to 26.6 months. The Panamanian cow-calf system reports an average annual birth rate of 55%, with a range of 35% to 60%, depending on the province. This reduced efficiency reported in the cattle production system is also reflected in low kilograms of weaned calves per cow exposed to AI or Bull (80kg) to 120 WW/cow exposed), high age at first calving (over 36 months), long calving interval (more than 450 days), and perhaps low-income returns ranging between 8 to 15% per dollar invested. The reproductive efficiency of a herd is one of the main components of a cow-calf system economically. Other important traits that affect the system efficiency and profitability are the preweaning traits: birth weight (BW) and weaning weight (WW). The lack of system efficiency and profitability is why different breeds have been introduced to the country to be used in crossbreeding systems to obtain the benefits of heterosis in growth and reproductive traits. The beneficial effects of crossbreeding on animal performance have been well established, benefiting low heritability traits such as those related to reproduction. For that reason, in tropical environments, matching the optimum cow numbers with the correct genetic potential in the appropriate production environment can maximize economic benefits. In the tropics, reduced pre- and post-weaning growth and reproductive efficiency are the main limiting factors in the cow-calf system. Preweaning traits are a combination of the direct genetic, maternal genetic, maternal permanent environment, and temporary environmental effects. The challenge for farmers in Latin American countries is to identify those animals that achieve maximum productive performance in a given agro-ecological environment, and to maintain a balance between longevity and generation intervals, in order to obtain the greatest genetic gain per unit of time. Knowledge of the genetic effects of breeds and their crosses in various climatic and forage conditions can be used to identify optimal breed combinations and crossbreeding systems for existing markets. Based on the heterogeneity of herds in tropical regions due to the introduction of multiple breeds and the different crossbreeding systems utilized, it is necessary to carry out a multibreed evaluation that includes all crossbred and purebred individuals into a single analysis and accounting for the direct and maternal breed and heterosis effect evaluation. As we mentioned above, different breeds have been introduced in Panamá, but no genetic evaluation program has been developed in the country, to improve the efficiency of cow-calf production. However, it is important to evaluate the breed groups and heterosis effect through productivity indicators to know the relative performance of the breeds and crosses of Zebu and Bos taurus cattle in the cow–calf system. Therefore, the objectives of this study were to determine heterosis and breed percentage effects on reproductive performance and preweaning traits in a multibreed beef cattle herd in Panama. For this, traits like age at first calving (AFC), calving interval (CI), gestation length (GL), birth weight (BW), and weaning weight (WW) that constitute important elements of the breeding objective of beef cattle producers were selected as the traits to evaluate in this study. All the reproductive and preweaning data utilized in this investigation was produced by a multibreed cattle population of the Livestock Experimental Station of Panama Agricultural Innovation Institute (IDIAP) in Gualaca, province of Chiriqui, Republic of Panama. The herd was comprised of the following genetic groups and breed percentage combinations: tropical adapted Brahman (BR), Nellore (Ne), Undefine Bos indicus (BI), Guaymi Creole (CR), Senepol (SP) Romosinuano (RS); Bos taurus (BT), Simmental (SM), Angus (AN), Red Angus (AR), Limousin (LM), Charolais (CH), Wagyu (WA), and Others (OTH); crossbreeds (CX), Beefmaster (BF), Three CX (F1 x different BT), R1(Backcross BR), R2 (Backcross BT), Composite (combination of at least 4 different breeds with less than 25% of Zebu), Upgraded Brahman (87.5% BR 12.5% BT), B1 (62.5% Zebu + 37.5% BT), B2 (62.5% BT + 37.5% Zebu). In general, this dissertation was divided into three different studies according to the physiological status of the individual producing the phenotypic record (e.g., calf, heifer, and multiparous cows). The first study estimated the influence of heterosis and breed percentage on age at first calving (AFC). An animal model was utilized to estimate variance components using data from 619 cows and 1,142 individuals in the pedigree from the multibreed herd with data collected between 2000 to 2019. The average AFC was 42.7 ± 10.5 months, with an estimated regression coefficient for AFC on heterosis of -0.046 ± 0.009 month/percent of outcross. Lower AFC was observed for the F1, R2, and B2, with 39.8 months, 39.9 months, and 39.5 months, respectively. A reduction in AFC was also observed for the Beefmaster (-0.13 ± 0.05 months) and the OTHER category (-0.14 ± 0.04 months). A heritability of 0.17  0.10 was estimated for AFC. These results suggest that heterosis had a beneficial influence on AFC measurements in a multibreed beef cattle herd in Panama. The second study focused on estimating the influence of heterosis and breed percentage on calving interval (CI) and gestation length (GL), and the correlation between age at first calving (AFC) and CI. Calving performance data included 1,291 repeated observations of CI and GL from 502 cows with a 3-generation pedigree consisting of 2,840 individuals in the pedigree with data collected between 2000 to 2021. A repeated records animal model was utilized to estimate variance components for both CI and GL. Additionally, a bivariate animal model was used to estimate the genetic correlation between CI and AFC. The average CI was 572.6 ± 140 days, and for GL was 284.2 ± 6.3 days, for this population. The regression of CI and GL on heterosis was not significant. A lower CI was observed for the F1, and Three CX, translating to 558.7 days and 567.2 days, which represents 2.3% and 1.3% reduction in CI, respectively when compared to the Zebu group. Calving interval was estimated to be lowly heritable (0.037 ± 0.026), however, a positive genetic trend over the duration of the study. The analysis between CI and AFC revealed a moderate genetic correlation (0.49 ± 0.36) which allows the establishment of a selection program to improve AFC and CI, due to the pleiotropic effect, which would improve the fertility of this multibreed herd in Panama. Finally, the third study aimed to estimate the influence of heterosis and breed percentage on birth weight (BW) and weaning weight (WW). Data from 900 calves with 2,843 individuals in the pedigree was utilized in a bivariate animal model for BW and WW was utilized to estimate variance components. The estimated regression coefficient for BW on heterosis was not significant, however, for WW was 0.072 ± 0.027 kg/percent of outcross. Lower BW and WW were observed for the Japanese, and B1, while R2 and Upgrade had the highest average WW. Heritability for BW was found to be low 0.14 ± 0.06 and moderate for WW 0.26 ± 0.09. The proportion of variation of WW accounted by the maternal permanent environment for WW was 0.2 ± 0.09. The estimated genetic correlation between additive genetic BW and WW was 0.63 ± 0.30, while a negative, additive genetic correlation was observed for WW and WW maternal -0.43 ± 0.37. These results suggested that heterosis had a beneficial influence on WW but a limited effect on BW. Additionally, increasing the percentage of WA and BR negatively influenced WW measurements in this multibreed population.
  • ItemOpen Access
    Pre-slaughter factors affecting mobility, blood parameters, bruising, and muscle pH of finished beef cattle in the United States
    (Colorado State University. Libraries, 2023) Sullivan, Paxton, author; Edwards-Callaway, Lily, advisor; Hess, Ann, committee member; Nair, Mahesh Narayanan, committee member
    Decades of work have focused on reducing fear, stress, and discomfort in cattle moving through the pre-slaughter phase by improving and promoting low-stress animal handling, transportation, and management processes. Even still, there is limited information about the effects of pre-slaughter factors on animal welfare and meat quality outcomes in finished cattle in the United States. The objective of this study was to track individual animals through the slaughter process to identify pre-slaughter factors associated with key welfare and quality outcomes. A total of 454 cattle from one slaughter facility were included in the study. Pre-slaughter factors assessed included: distance traveled, lairage density, lairage duration, season, and truck waiting time. Animal-related characteristics, i.e., body weight, breed, and sex, were also recorded. One trained observer scored mobility of all study cattle using the North American Meat Institute's 1-4 scale (i.e., normal to extremely reluctant to move). Postmortem, exsanguination blood was collected on animals and analyzed for cortisol, creatine kinase, and lactate. Carcass bruising was scored using a modified version of the National Beef Quality Audit's bruise scoring methodology (i.e., no bruise, one bruise that was ≤ the size of a deck of cards, one bruise that was > than the size of a deck of cards, and multiple bruises). Ultimate muscle pH was measured 32 to 36 hours postmortem. Multi-predictor models were selected for each outcome variable using Aikake Information Criterion (AIC). Continuous outcome variables were analyzed using linear mixed-effects models and categorical outcome variables with mixed-effects logistic regression models. Increased truck waiting time was associated with increased cortisol (P = 0.04) and lactate (P = 0.02) concentrations. Similarly, an increase in lairage duration was associated with an increase in creatine kinase (P = 0.05) and the odds of cattle being bruised (P = 0.03). Less space allowance per animal in lairage was associated with increased odds of cattle having impaired mobility (P = 0.01). There was a seasonal effect for many of the measured outcomes; the summer season was associated with greater lactate concentrations (P < 0.0001), increased odds of impaired mobility (P < 0.0001), and increased odds of carcass bruising (P = 0.003). The findings of this study indicate that many of the pre-slaughter factors assessed influence key welfare and meat quality outcomes of finished beef cattle, warranting future research and consideration.
  • ItemOpen Access
    GWP* of U.S. beef and dairy systems
    (Colorado State University. Libraries, 2023) Molina Plaza, Erick, author; Dillon, Jasmine, advisor; Archibeque, Shawn, committee member; Denning, Scott, committee member; Sheehan, John, committee member
    Global warming potential (GWP) is used to quantify the impact that greenhouse gases (GHG) have on the warming of the Earth's atmosphere relative to carbon dioxide (CO2). GWP* is a metric that is used to better quantify short-lived climate pollutants (SLCP) such as methane, hydrofluorocarbons, and sulfur dioxide. GWP* allows SLCP to be more consistently expressed by equating a change in the emission of the SLCP to a one-off pulse emission of CO2. Therefore, GWP* can be positive or negative. The objective of this work was to compare the GWP* and GWP100 for U.S. beef and dairy systems using livestock methane emissions data from the Food and Agriculture Organization (FAO) and the Environmental Protection Agency (EPA). Total methane emissions for this study are the sum of enteric and manure methane emissions. GWP100 was greater than GWP* for both beef and dairy systems using both datasets, with the exception GWP* for dairy using the EPA data. Dairy GWP* calculated using the EPA data was lower than GWP100 from 1990–2000, after which point on it became greater than GWP100 and continued increasing annually, because the emission factors used by the EPA increased annually, and the difference between weighted emissions from that year and the weighted emissions from 20 years prior surpassed the current emissions used in GWP100. Overall, the GWP* of EPA dairy increased by 507% from 1990–2020. The primary drivers of the differences in GWP* and GWP100 with the EPA dataset are the use of methane emission factors for manure methane, which increase yearly, and the use of a larger dairy population estimate than FAO. The EPA emission factors increase yearly based on the trend towards larger farm sizes managing more liquid manure, therefore produce more manure methane emissions. The dairy GWP* using EPA data was greater than the beef GWP* every year, despite greater total methane emissions for beef than for dairy, because the average rate of change for dairy (29.8 kt of CH4/yr) was greater than the average rate of change for beef (9.4 kt of CH4/yr). Accounting methods play a key role in the amount of methane emissions that are calculated, and thus how GWP100 and GWP* are calculated. The EPA larger population estimate and annual increase in manure methane emission factors led to greater GWP* and GWP100 values for the EPA data than for the FAO data for both beef and dairy systems. Data source is critical to the policy implications of GWP* and GWP100 for livestock systems, as evidenced by the differences in GWP* and GWP100 results between datasets.
  • ItemOpen Access
    Impact of growth implants and tannin supplementation on enteric methane emissions and estimated nitrogen excretion in grazing stocker steers
    (Colorado State University. Libraries, 2023) Kutz, Mesa, author; Stackhouse-Lawson, Kim, advisor; Garry, Franklyn, committee member; Finck, Jessica, committee member; Place, Sara, committee member
    The objective of this experiment is to evaluate the effects of a growth-hormone implant (Revlor-G, Merck Animal Health., Rahway, NJ; 40 mg of trenbolone acetate and 8 mg of estradiol) and tannin supplementation (Silvafeed BX, Silva Team, San Michele Mondovi CN, Italy) on enteric methane (CH4) emissions and estimated nitrogen (N) excretion in stocker cattle. Grazing stocker steers (n = 20; initial BW = 343 ± 14 kg) were trained for three weeks to use a portable automated head-chamber system (AHCS; C-Lock Inc., Rapid City, SD) and SmartFeed Pro automated feeder (C-Lock Inc., Rapid City, SD) for dietary supplementation. After the training period, steers were randomly assigned to one of four treatments: 1) no tannin and no implant (Control [CON]); 2) tannin supplement and no implant (Tannin [TAN]); 3) implant and no tannin (Implant [IMP]); and 4) tannin supplement and implant (Implant + Tannin [IMP + TAN]). The tannin was offered at 0.30% DM tannin intake through 0.5 kg/hd/d sweetfeed mix (Sweetfeed Mix, AgFinity., Eaton, CO). Treatment groups without tannin (Control and Implant) received the same sweetfeed mix ration at 0.5 kg/hd/d without the tannin supplementation. Daily forage intake was estimated using the NRC (1996) forage intake prediction equation. Total intake included the estimated forage, bait (alfalfa pellets from AHCS), and sweetfeed mix. Across the experiment, no animal consistently consumed all 0.5 kg/hd/d of the offered sweetfeed mix. On average, the CON cattle consumed 0.32 kg/hd/d, the TAN group consumed 0.41 kg/hd/d, the IMP cattle consumed 0.44 kg/hd/d, and the IMP + TAN group consumed 0.36 kg/hd/d. Moreover, the lack of a tannin x implant interaction (two-way ANOVA; P=0.24) also suggested sweetfeed mix intake did not depend on either treatment level. In response, we evaluated the effect of tannin supplementation and a growth-promoting implant in a separate analysis and data were analyzed with treatment levels as follows: I1) NO-IMP: All animals that did not receive growth implant; I2) IMP: All animals that did receive growth implant; T1) NO-TAN: All animals that did not receive tannin supplement; T2) TAN: All animals that did receive tannin supplement. The sample size for the evaluation of the tannin effect included: NO-TAN (n = 9; 5 animals were implanted with growth promotant) and TAN (n = 9; 5 animals were implanted with growth promotant), while the growth implant effect included: NO-IMP (n = 8; 4 animals were supplemented tannin) and IMP (n = 10; 5 animals were supplemented tannin). Supplementation with tannin did not impact, animal performance metrics (initial body weight, final body weight, and ADG) across the entire study or within early or late study periods (P ≥ 0.33). Steers supplemented with the NO-TAN supplement tended (P ≥ 0.10) to have greater dry matter intake (DMI) and less CH4 yield (MY) compared to cattle supplemented with TAN. There was no effect of tannin supplementation on enteric CH4 production (g/d; P = 0.24) and EI (P = 0.23). N utilization as measured through blood urea nitrogen (BUN), urine N, fecal N, or fecal P was not different among TAN and NO-TAN animals (P ≥ 0.12). Growth-promoting implants did not affect initial body weight (P = 0.86) or final body weight (P = 0.51). There was no effect of growth hormone implant on average daily gain (ADG) during the 90-d of the study (P = 0.80). However, IMP steers tended (P = 0.10) to have greater ADG during the first half of the study (d 0 to 45). Implanted steers also had greater forage (P = 0.05) and bait intake (P = 0.02), and numerically greater total DMI (P = 0.13) over the 90-d study. For IMP steers, there was no effect (P > 0.19) of growth implant on methane (CH4) production or emission intensity (EI; g CH4/kg gain) during the 90-d study. However, IMP steers had decreased (P = 0.03) EI during the first period. Additionally, the IMP steers tended to have less CH4 yield (MY; g CH4/g DMI, P = 0.09) and BUN (P = 0.08) than NO-IMP steers. There was no growth-promoting implant effect (P > 0.30) on cattle urine and fecal N, creatinine, or fecal P. In summary, supplementing tannin in the diet of grazing stocker steers tended to reduce total estimated DMI but did not affect enteric CH4 emissions compared to steers that received no tannin supplement. Implanting steers with Revalor-G tended to 1) increase total DMI in the 90 d study, 2) increase ADG in the early period (d 0 to 45) and 3) decrease CH4 EI in the first 45 d post-implantation.
  • ItemOpen Access
    2022 National Lamb Quality Audit: Phase I: Supply chain perceptions of the U.S. lamb industry. Phase II: In-plant survey of carcass characteristics related to quality and value of fed lambs and mutton
    (Colorado State University. Libraries, 2023) Newman, Lauren, author; Stackhouse-Lawson, Kim, advisor; Place, Sara, committee member; Nair, Mahesh Narayanan, committee member; Garry, Franklyn, committee member; Finck, Jessica, committee member
    The U.S. sheep and lamb population has slowly declined over the last eight decades, from 56 million head in 1942 to five million head in January of 2023. Sheep, often referred to as mutton in the meat industry, are mature animals that have at least two permanent incisors, spool joints, and are typically over 24 months of age. Lambs are considered young animals that lack permanent incisors, have at least one break joint, and are usually less than 14 months (USDA,1992). The U.S. lamb industry faces competition from imported lamb from Australia and New Zealand that is less expensive. This imported product increases the lamb supply within U.S. wholesale and retail stores, which, along with increased production costs, has raised concerns about the future viability of the U.S. lamb industry. In response to this pressure, the lamb supply chain can prioritize attributes that both reduce production costs and promote consumer demand. The first step in this process is to measure data from production through lamb carcass quality characteristics, especially data captured in the manufacturing settings. Benchmarking is necessary to identify needs to drive quality enhancements and to ultimately drive improvement and profitability of the lamb industry. The current National Lamb Quality Audit (NLQA) seeks to fill this gap by capturing baseline data from broad scope of the supply chain through perception surveys and in-plant audits. This baseline information will inform the lamb value chain on the current perceptions and lamb quality characteristics that may aid in identifying attributes to reduce costs and increase consumer demand. The NLQA, conducted three times since 1992, assesses the industry's progress on various quality characteristics that ultimately affect consumer demand for lamb. The most recent audit, conducted in 2015, primarily focused on the foodservice segment of the industry. As sheep genetics, management practices, available resources, and consumers' needs and expectations constantly evolve, more frequent audits that capture the entire supply-chain should be considered. The 2022 NLQA audit is designed to repeat successful portions of the 2015 audit, including a new supply chain survey to assess perceptions about the U.S. lamb industry and in-plant carcass characteristics. In phase I, 155 surveys were conducted from May 2022 through September 2022 to understand and quantify perceptions of the U.S. lamb industry. The survey was administered using a software package (Qualtrics®, Provo, Utah) customized to develop a structured order of questions for each industry segment. The survey was distributed via in-plant visits, social media, and email. Survey respondents remained anonymous, each taking approximately ten minutes to complete. Statistical analysis was conducted in Microsoft Excel and the Qualtrics® software. Thirty-two states were represented, with 88 percent of respondents identifying as the owner/operator of their respective business or operation and 86 percent representing commercial breeding operations. Respondents were asked to rank topics based on importance to their operation from 1 (least important) to 10 (most important). Animal welfare (8.9), lamb quality (8.4), and sustainability (7.6) were of most importance to producers. Respondents were also prompted to rank significant challenges in the industry (1=most important and 10=least important). The most significant challenges identified were operation costs (3.04), market volatility (3.70), and labor (4.08). Open-ended responses for defining sustainability were sorted and narrowed in terms of descriptions to find commonalities between respondents. Central themes from respondents included environmental stewardship, profitability, and producing high-quality lamb products. Results from the survey will provide valuable insight to discern gaps and opportunities between producers' viewpoints and data collected in plants to develop educational material to improve lamb quality. For phase II, in-plant assessments were conducted in four of the largest U.S. commercial lamb processing facilities across six production days from June to September 2022. On each production day, 50 percent of carcasses harvested and chilled were surveyed. Both hide-on and hide-off carcasses (n=2,605) and chilled carcasses (n=2,464) were surveyed. On the harvest floor, trained auditors collected data on mud scores, breed type, presence of horns, sex, wool length, and physiological age indicator data. Additionally, hot carcass weight (HCW), measured fat thickness (MFT), and reported USDA yield and quality grades were collected in the cooler. The distribution and summary functions of JMP® Software were used to determine the frequency distributions, means, standard deviations, and minimum and maximum values. Data was analyzed using the Type III ANOVA procedure, and a pairwise comparison was analyzed for dependent variables by treatment using the least squared means procedure in the 'lsmeans' package, of R© with the Tukey HSD adjustment. Dependent variables were YG, calculated YG, HCW, and MFT. Significance was determined at P-value ≤ 0.05. Phase II used in-plant assessments to benchmark current carcass quality characteristics related value of the fed lamb and mutton industry in the U.S. Among the carcasses (n = 1,605) that were audited for sex, 63.2 percent were wethers, 31.5 percent ewes, and 5.3 percent rams. Two percent of the carcasses were presented with horns. Of the 2,604 carcasses evaluated, 40.2 percent were speckle-faced (white-face and black-face cross), 38.8 percent were white-faced, 18.3 percent were black-faced, 1.46 percent had natural characteristics, and 1.72 percent were hair sheep. The average mud score was 2.12, and the average wool length was 5.03 cm. Additionally, 87.1 percent of the 2,437 carcasses presented two break joints indicating lamb, 5.70 percent with one break joint indicating yearling mutton, and 7.18 percent with no break joints indicating mutton. The average HCW (n=2,464) was 39.9 kg, whereas the MFT was 0.97 cm. The USDA stamped yield grade was 2.71 and 68.5 percent graded choice (CH), 22.6 percent graded prime (PR), and 8.9 percent were not graded. The 2022 NLQA in-plant survey of carcass quality characteristics will provide a current benchmark for carcass characteristics of lamb processed in the U.S. The data from this study can help industry segments to understand and develop strategic initiatives to improve the quality of fed lamb and mutton.
  • ItemOpen Access
    Genetic relationships between sex-specific traits in a crossbred beef cattle population
    (Colorado State University. Libraries, 1993) Speer, Nevil, C., author; Brinks, James S., advisor
    Data used were obtained from the Fort Keogh Livestock and Range Research Laboratory (LARRL), Miles City, Montana. Data were from a crossbreeding experiment involving Hereford, Angus and Charolais cattle collected from 1962 to 1977. Traits studied and considered separate with respect to sex, included male and female birth weight (BWM and BWF), weaning weight (WWM and WWF), and postweaning average daily gain (ADGM and ADGF). Other traits studied were average adjusted mature weight (MW) of cows and fat thickness (FT), ribeye area (REA), yield grade (YG), quality grade (QG) and days on feed (DOF) of bulls and steers slaughtered at a weight constant endpoint of 1000 - 1050 lb. Multi-trait sire-maternal grandsire REML analyses were performed on straightbred and crossbred Hereford, Angus, and Charolais cattle. Observations on 2888 animals contributed to development of the A-inverse which represented relationships among 138 sires and maternal grandsires. Models for BWM, BWF, WWM, WWF, ADGM, ADGF, and MW analyses models included birth year, age of dam (2, 3, 4, 5+) and linear regression on weaning age. The DOF analysis model included birth year, age of dam, sex of calf (bull vs steer), age of dam-sex of calf interaction and linear regression on weaning age. Carcass trait (FT, REA, YG, QG) models included birth year, age of dam, sex of calf, age of dam-sex of calf interaction and linear regression on carcass weight. Linear regressions on individual breed percentage, combined reciprocal cross percentage (individual heterosis), dam breed percentage and dam combined reciprocal cross percentage (maternal heterosis) were also included in all models for analyses of all traits of interest. Correlations between direct components of birth weight, weaning weight, and postweaning average daily gain considered separately between male and female calves were .93, .90 and .74 respectively. The correlation between direct components of MW and DOF was -.66. Correlations between direct components of MW and carcass traits were -.54, -.18, -.18, and .41 for FT, REA, YG and QG, respectively. Correlations between maternal components of birth weight, weaning weight, and postweaning average daily gain considered separately between male and female calves were .86, .98 and .42, respectively. The correlation between maternal components of MW and DOF was -.71. Correlations between maternal components of MW and carcass traits were .40, .10, .08, and -.06 for FT, REA, YG and QG, respectively. Correlations between mat-dir and dir-mat of the same traits studied were moderate and ranged from -.44 to .47. Predictions of correlated responses in mature weight per standard deviation of direct response in male carcass traits were -32 lb, -13 lb, -10 lb, and 31 lb respectively for FT, REA, YG and QG. Correlated response predictions indicate selection for improved carcass cutability on a weight constant basis (increased leanness and decreased yield grades) would increase mature weight while selection for increased ribeye area and decreased quality grade scores (favorable) on a weight constant basis would result in decreased mature weights of females. Strong selection pressure for leanness may be antagonistic to commercial beef producers since results suggest sires selected on the basis of reducing fat in steer progeny also produce females that are larger at maturity when cattle are slaughtered at a constant weight endpoint. It should be noted, however, relationships between carcass traits and mature weight may differ when cattle are slaughtered at a constant age endpoint.
  • ItemOpen Access
    Processes to improve storage shelf-life and palatability of beef
    (Colorado State University. Libraries, 2023) González Sánchez, Sara Victoria, author; Nair, Mahesh N., advisor; Geornaras, Ifigenia, advisor; Morgan, J. Brad, committee member; Gutierrez-Rodriguez, Eduardo, committee member
    Three studies were conducted to evaluate processes to improve the storage shelf-life and palatability of beef. The first two studies evaluated the effects on retail shelf-life and palatability characteristics of beef following Suspended Fresh® storage. Suspended Fresh® (SF) is a patented, proprietary, trademarked process that allows the storage of beef muscles at temperatures at or slightly above their freezing point to slow down microbiological spoilage while maintaining the product's fresh status. These studies evaluated the impact of 60, 75, or 90 d of storage in SF (-2.7±0.3°C) on the retail shelf-life and palatability characteristics of steaks derived from inside rounds (IR), bone-in ribeyes (RE), and striploins (SL) from 10 (n=10) upper two-thirds Choice beef carcasses. Two steaks fabricated from each subprimal were vacuum-packaged, wet-aged for 21 d (3°C), and frozen (-20°C) for Warner-Bratzler shear force (WBSF) and sensory analyses. These steaks served as the control with regard to storage condition and time. The remainder of each subprimal was fabricated into three portions, and after vacuum packaging, were randomly allocated to an SF storage time of 60, 75, or 90 d. After each storage time, five steaks were fabricated from the subprimal pieces, overwrapped, and placed in a retail display case (3°C) under continuous fluorescent light for 7 d. Another two steaks were vacuum-packaged and stored at -20°C until WBSF and consumer sensory evaluations. Consumers (N=238) evaluated each sample for juiciness, tenderness, flavor liking, and overall liking. Instrumental and trained visual color were evaluated daily during retail display, and aerobic bacterial populations (APC), lactic acid bacteria, and Pseudomonas spp. were enumerated on days 0, 2, 4, and 7. Data were analyzed in R using a factorial design for the microbial counts or a split-plot for the rest of the analyses. Least-squares means were separated using a significance level of α=0.05. For all cuts, initial redness (a* values) of SF60 steaks were lower (P < 0.05) than SF75 and SF90 steaks. In general, irrespective of SF storage time or retail display day, trained panelists did not detect differences in lean color and discoloration of steaks. For all cuts, the APC of SF60 steaks on days 0, 2, and 4 of retail display were lower (P < 0.05) than those of SF75 and SF90 samples. The WBSF values decreased (P < 0.05) with increased storage time for all the cuts. Similarly, the consumer tenderness rating scores of IR and SL generally increased with the SF storage time. However, storage time did not influence (P ≥ 0.05) the juiciness, flavor, and overall liking of any cuts. The results of this study suggest it would be feasible to extend the storage time of beef while preserving or improving the sensory quality when held at optimal conditions above the freezing temperature. The third study was conducted to evaluate the effects of different temperature and time treatment combinations (1A: 56.1°C and 71 min; 1B: 56.1°C and 150 min; 1C: 56.1°C and 240 min; 2A: 61.7°C and 8 min; 2B: 61.7°C and 150 min; 2C: 61.7°C and 240 min) of sous vide cooking on the palatability of beef biceps femoris. Beef biceps femoris were sliced into 1.6-cm steaks, vacuum packaged as 4.5 kg bags, and randomly assigned to one of the six treatments with 16 packages (n=16) per treatment. Cooked and chilled packages were weighed, and then the weight of the meat was taken to measure cooking loss. Weighed samples were divided into two halves: one was left non-marinated, and the other was assigned to marination. Two 1.6-cm non-marinated steaks were randomly selected and cut in half to measure the internal cooked color. Additionally, non-marinated and marinated steaks were randomly selected for WBSF and sensory analysis by a trained panel. Data were analyzed using a complete randomized design in R with a significance level of α=0.05. The cooking loss of samples increased as the temperature and dwell time combinations increased (P < 0.05). Internal redness of steaks decreased (P < 0.05) with increased temperature and dwell time. The only major difference in WBSF and the trained sensory panel results was between treatment 1C (56.1°C and 240 min) and 2A (61.7°C and 8 min), where 1C samples had lower WBSF values and higher perceived tenderness scores than 2A samples. These results suggest that biceps femoris samples can be cooked at conditions examined in this study with minimal impact on palatability, allowing producers more flexibility with cooking time to optimize production time and energy while reducing cooking loss. Overall, the findings of these studies should be useful to the beef industry as they consider strategies for improving the storage shelf-life and palatability of beef.
  • ItemOpen Access
    Life cycle environmental impacts of utilizing hemp seed meal as a protein source in sheep feedlot rations
    (Colorado State University. Libraries, 2023) Clark, Samantha Maye, author; Dillon, Jasmine, advisor; Archibeque, Shawn, committee member; Nachappa, Punya, committee member; DiVerdi, Joseph, committee member
    Hemp seed meal is a protein-rich byproduct of the hemp industry, obtained from the cold press extraction process used to produce hemp oil. The objective of this work was to evaluate the environmental impact of using hemp seed meal as a protein supplement in sheep production. A cradle-to-gate life cycle assessment (LCA) was conducted on three sheep production systems which differed in the feedlot phase: one fed a feedlot ration containing soybean meal as the protein source (soybean meal diet), one fed hemp seed meal in the feedlot ration (hemp diet), and one fed organic hemp seed meal in the feedlot ration (organic hemp diet). Animal performance data were collected from a nutrition trial. Hemp production, harvest, and processing data were provided by a hemp product company. Economic and physical allocation were applied to the hemp diet systems, and the ReCiPe Midpoint (H) methodology was used to calculate the global warming (i.e., carbon footprint), water consumption, land use, and fossil resource scarcity impacts on a per kg lamb live weight basis for each system. Carbon footprint ranged from 10.1 to 11.4 kg CO2eq/kg LW, water consumption ranged from 1.3 to 4.2 m3/kg LW, fossil resource scarcity ranged from 0.5 to 0.8 kg oil eq/kg LW, and land use ranged from 2.8 to 6 m2a crop eq/kg LW. Impact assessment results were not sensitive to a 10 or 20% increase in electricity demand at processing. The use of IPCC Tier 2 methods for estimating enteric methane emissions from sheep resulted in a 7.5–8.5% increase in the carbon footprint, relative to a mechanistic equation present in the Ruminant Nutrition System model. Physical allocation resulted in greater impacts of the hemp diet systems than the soybean diet systems for all categories except land use. However, economic allocation resulted in greater impacts for the soybean diet systems than the hemp diet systems for all categories evaluated. This was explained by inherent differences between the allocation method, as physical allocation attributed 80% of the environmental burden to hemp seed meal, while economic allocation attributed 0% of the environmental burden to hemp seed meal due to the current lack of an economic value for hemp seed meal. The production volume of dependent products ("dependent products", or products for which a change in demand does not affect production volume, commonly referred to as co- or byproducts) are driven by monetary value of the determining product (the product for which a change in demand affects the production volume), but relationships between co-products change overtime. Therefore, as the hemp industry continues to develop, an economic value may be placed on hemp seed meal with implications for its relative ability to reduce the environmental impacts of livestock production. As agricultural industries strive to become more environmentally efficient, they must be adaptive to changes in both monetary value and environmental impact, which are intrinsically related. This research demonstrated the importance of allocation choice in assessing the impact of feeding byproducts on the environmental impact of livestock production systems. Economic allocation better reflected the monetary driving factor for hemp production than physical allocation. As such, the inclusion of hemp seed meal in a feedlot ration reduced the environmental impact of sheep production systems.
  • ItemOpen Access
    Temperament and maternal behavior of beef cattle
    (Colorado State University. Libraries, 2023) Rogers, Corley, author; Grandin, Temple, advisor; Engle, Terry, committee member; Archibeque, Shawn, committee member; Garry, Frank, committee member
    This thesis contains both a literature review and an observational study about temperament and maternal behavior of beef cattle. The literature review covers maternal behavior, maternal protectiveness, temperament, and stress in beef cows. The aim of the experiment was to compare the distance maternal protective behaviors were performed against measurements of temperament. The results of the study showed very little correlation between how the cow defends her calf and her behavior in the chute. The overall aim of this thesis was to was to address the paucity of data regarding how maternal protectiveness and temperament are related and if there is an inadvertent increase in the potential for predation if breeding for a docile temperament.
  • ItemOpen Access
    An integral approach for management challenges in the dairy industry
    (Colorado State University. Libraries, 2023) Herrera, Natalia, author; Pinedo, Pablo, advisor; Velez, Juan Santiago, committee member; Holt, Timothy, committee member
    A growing body of literature recognizes the importance of including an integrated approach to animal welfare and employee well-being in the dairy industry. The current thesis aims to describe this integral approach by presenting two research projects developed in a commercial dairy under the same management. Hence, an animal welfare pilot study was performed on a dairy farm located in northern Colorado, and an employee well-being study was developed on three dairy farms, two located in northern Colorado and one in northern Texas. Both projects were performed during the year 2022 and the dairies are administrated by the same management. The overall structure of this thesis takes the form of three chapters, including each perspective previously analyzed in the current management challenges explored in the dairy industry. Chapter one presents an extensive literature review of both approaches identified as management challenges in the dairy industry. Then, chapter two analyses the results of an online survey undertaken from September through November 2022 that aimed to explore employee adaptation, perception, and understanding of technology in the dairy farm. In order to accomplish the goal of this pilot study, the online survey completed by two-hundred-sixty-six employees was analyzed and the results are presented in chapter two. Chapter three presents the results of an observational study done on cow-calf behavior from the expulsion of the calf up to the separation in a dairy system located in northern Colorado. One-hundred-sixty-seven calving that occurred from May to June were analyzed and the results are presented in chapter three. Results are briefly described next. First, from the adaptation, perception, and understanding of technology in the dairy farm study, employees recognize and have positive feelings towards the technology implemented at work, where they highlighted the understanding of its benefits, and recognized the technology as a tool that helps them to be more efficient. However, the challenges to adapting to new technology were mainly determined to be personal limitations, such as not knowing the language of the technology and impairments to seeing. Also environmental limitations were recognized by the employees such as cold weather, wind, or an environment that is too dark or too bright. Lastly, the level of perception of technology was found to be associated with the level of education and level of English of the employee, but no significant differences were identified by age or gender. Findings are promising and the current thesis invites the academia to extended this type of research in other livestock operations that adopt precision livestock farming technology. Second, from the cow-calf behavior from the expulsion of the calf up to separation in a dairy system research, with an average time of 2,489 seconds together, the predominant behavior found by the dam was the intensive licking towards their calf, and secondary particular behaviors were lying down after calving, aggressive behavior upon a surrogate cow, and a following behavior upon separation. On the calf side, the main behaviors were licking the cow, and mobilizing with their two front hooves. Less common behaviors were standing up, reaching the udder, suckling, and looking at her cow upon separation. Moreover, animal-level variables that were associated with these behaviors were found to be parity and calving difficulty. Also, for environmental-level variables, the drop time, calving in the patio, and temperature were associated with these behaviors as well. In general, no significant associations were found for twins, calf gender, and heat index. Lastly, when the future health performance of both animals was analyzed, only the stand-up behavior of the calf was significantly associated with an increased average daily gain weight from birth to weaning, compared to calves that did not stand up. The novel findings presented in this thesis will help dairy management to better understand latent challenges in the industry with an integral approach that includes animal welfare and employee well-being. This study extends the knowledge of cow-calf contact systems by exploring the animal behavior right after calving and up to separation and provides a comprehensive assessment of adaptation, perception, and understanding of precision livestock farming technologies by the dairy employee. The conclusions from this thesis will add to the rapidly expanding field of integrating animal and employee health into integral strategies for current management challenges in the dairy industry.
  • ItemOpen Access
    Dairy heifer habituation to the milking routine: stress in the primiparous cow and its impacts on behavior and production
    (Colorado State University. Libraries, 2023) Kness, Danielle, author; Grandin, Temple, advisor; Pinedo, Pablo, committee member; Edwards-Callaway, Lily, committee member; Garry, Franklyn, committee member
    The transitional period surrounding parturition and onset of lactation is undoubtedly a stressful time in the life of a dairy cow. This is especially true for primiparous cows, who have no previous experience to the milking routine and must become accustomed to increased contact with human caretakers as well as the host of novel sights, sounds, smells and sensations in the milking parlor. Behaviors stemming from acute stress have the potential to increase risk of injury to parlor employees, who must be located close to the cows in order to perform their duties. Even so, the specific changes in cow behavior in the parlor over the course of the first lactation are not well documented, presenting a challenge to farm managers who wish to train employees in primiparous cow management. The main focus of this thesis is to present current research on this topic, as well as present new research regarding specific, daily changes in primiparous cow behavior during the first lactation. Chapter one is a review of the current literature regarding sources of stress in first-lactation heifers and their impacts on various aspects of cow behavior and production, as well as on worker safety and wellbeing. The roles of precision livestock farming technologies on modern dairy farms are also discussed in this chapter, as well as the potential of these technologies for dairy cow welfare management and research. The objective of chapter two is to describe the dynamics of milking unit kick-off in primiparous and multiparous cows during the first three months of lactation. Data were collected from 199 primiparous (PRI) and 670 multiparous (MUL) cows who calved between August and November of 2020. From 3 days in milk (DIM) until 90 DIM, data were downloaded daily for each cow from the farm's software program. The main variables of interest were parity category and milking machine kick-offs (KO), which were reported by the milking system when an abrupt interruption in the milk flow occurred. KO events were used in our analysis as a proxy for habituation to the milking routine, and were analyzed by DIM. We found that proportions of KO were greater in PRI than in MUL throughout the monitoring period, and that when analyzed by DIM, first-lactation cows showed a non-linear trend of kick-offs. This indicated that changes in behaviors displayed during the habituation process are not linear, but instead are more complex. Chapter 3 is an analysis of additional data that were collected during the study presented in chapter 2. Study participants were the same, but our goal in this chapter was to investigate any possible relationships between rates of machine kick off, daily changes in milk yield, and occurrence of mastitis during early lactation. Cows with varying frequencies of machine kick-offs were categorized into quartiles. Quartiles were then analyzed for potential interactions with milk yield and mastitis occurrence. Overall, we found no differences in milk yield between KO quartiles, but both primiparous and multiparous cows in the quartile with the highest KO rates had higher rates of mastitis.
  • ItemOpen Access
    Ground beef pathogen dynamics and the current scope of the impact of foreign materials on meat and pet food products
    (Colorado State University. Libraries, 2023) Carlson, Chloé M., author; Martin, Jennifer, advisor; Engle, Terry, committee member; Delmore, Lynn, committee member; Webb, Colleen, committee member
    This thesis provides an overview of ground beef consumption and the state of microbial testing of ground beef. The study focuses on understanding dynamic growth relationships between pathogenic and non-pathogenic bacteria in ground beef and how this information might be used to predict the presence of pathogens or the onset of microbial spoilage. Additionally, this thesis examines current United States Department of Agriculture Food Safety Inspection Service (USDA-FSIS) and the Food and Drug Administration (FDA) regulations around foreign material adulterated meat and pet food. The review looks at the challenges between the two regulatory bodies and provides guidance for improvement.
  • ItemOpen Access
    A pilot study of behavioral and physiological markers of stress in horses during equine-assisted learning for youth with social-emotional concerns
    (Colorado State University. Libraries, 2023) Singh, Ashley, author; Grandin, Temple, advisor; Peters, Caiti, advisor; Matlock, Sarah, committee member; Nett, Terry, committee member
    Equine Assisted Learning (EAL) is an increasingly popular service in providing comfort and life skills for youth who have social-emotional concerns. There is mixed evidence in previous research that shows increased stress in horses in EASs who are interacting with the population of youth with social- emotional concerns. This pilot study aimed to look physiological and behavioral indicators of stress in horses involved in equine assisted learning for youth with social- emotional concerns. This within-subject design included 11 horses and 18 human participants. Indicators of equine stress included salivary cortisol, eye temperature, and equine behavior. On average, indicators of stress in horses were not significantly different while the horses interacted with youth with social- emotional concerns compared to a control condition. There was a significant condition x week interaction effect such that horses demonstrated higher levels of cortisol in week 3 while interacting with youth with social- emotional concerns compared to the control condition, but this difference did not exist by Weeks 5 and 7. These condition by week interaction effects did not exist in equine eye temperature or behavior. This study provides evidence that interacting with youth with social- emotional concerns was not more stressful for horses that interacting with another population that commonly participates in EAL.
  • ItemOpen Access
    Strategies to maintain market access for pork and enhance functionality of beef proteins
    (Colorado State University. Libraries, 2023) Cochran, Hannah, author; Martin, Jennifer, advisor; Bosco-Lauth, Angela, committee member; Garry, Franklyn, committee member; Roman-Muniz, Noa, committee member
    African swine fever is a high-consequence foreign animal disease endemic to sub-Saharan Africa and the island of Sardinia. The U.S. is the world's third largest pork producer, and ASF introduction would severely disrupt the pork supply chain, emphasizing a need to protect market access for U.S. proteins. However, niche producers raising swine intended for exhibition may not follow stringent biosecurity protocols and livestock show circuits may promote untracked animal movement across the country, potentially exacerbating virus spread in the event of ASF incursion into the U.S. Two Qualtrics surveys designed to evaluate knowledge, understanding, and perceptions of ASF and biosecurity principles of youth swine exhibitors and adults involved in the exhibition swine industry were distributed via flyers, emails, and canvassing at livestock shows. Youth exhibitors (age 21 and under) answered questions assessing their knowledge and provided basic demographic information, including their home state and states to which they traveled for exhibitions. Adult respondents answered the same questions assessing their knowledge and provided information on their time involved in the swine industry and number of shows attended by the youth they advise (if any). Youth respondents (n = 127) lived in 14 states and exhibited in 23 states, with 35% and 28% holding membership in state and national swine organizations, respectively. When provided with a list of ASF clinical signs, 34 individuals (26.9%) correctly identified all symptoms. Twenty-nine individuals (23%) incorrectly responded that ASF has been found in the U.S., and ten (7.9%) believed the virus cannot spread between pigs. Increased biosecurity understanding in youth exhibitors showed a significant relationship with an increase in years involved (p<0.05). Adult respondents (n = 211) had been involved in the swine industry for an average of 21 years, and the youth they advised attended 14 exhibitions in an average year. Nearly all adults (90.5%) identified direct contact with infected animals as a method of ASF transmission, while far fewer (36.39%) identified animal feed as a possible mechanism of transmission. These responses indicate highly varied knowledge of symptoms, routes of transmission, and biosecurity recommendations. Youth membership in state or national swine organizations offers a route for outreach and educational activities to enhance foreign animal disease preparedness, and adult presence at swine exhibitions allows for a wide variety of programming for all ages to better serve all levels of understanding. Fluctuations in the beef supply chain due to COVID-19 triggered discussions on methods to fully utilize edible proteins from beef carcasses, such as collagen. One potential method is the addition of collagen powder to beef frankfurters to replace a fraction of lean grind. The inclusion of NOVAPRO® collagen powder to beef franks at three hydration levels resulted in no significant differences (p>0.05) in water activity, pH, or shear force values between the treatment groups. Additionally, trained sensory panelists did not discern differences between treatment or control samples when asked to rate attributes that included beef flavor intensity, seasoning intensity, springiness, and mouth coating, indicating that NOVAPRO® powder could be added to processed meat products to reduce costs without compromising product quality.
  • ItemOpen Access
    Effects of trace mineral source and concentration on production parameters throughout one cow-calf production cycle
    (Colorado State University. Libraries, 2023) Hallmark, Harrison, author; Engle, Terry, advisor; Ahola, Jason, advisor; Garry, Franklyn, committee member
    An experiment was conducted to evaluate the effects of Cu, Zn, and Mn supplementation on mineral status, production parameters, and cattle performance in a rangeland environment throughout a one -year period in eastern Colorado. One hundred and eighty multiparous crossbred (Angus and Angus x Hereford) beef cows were blocked by body weight, age, and gestational status and randomly assigned to 1 of 3 free-choice mineral treatments (n = 60 cows per treatment). Treatments were then assigned to 1 of 9 replicates (n=20 cows per replicate), resulting in 3 replicates per treatment. Treatments consisted of, 1) 1X NASEM (2016) sulfate base source, 2) 1X NASEM (2016) Intellibond source, or 3) 0.5X NASEM (2016) Intellibond source. Treatments 1 (1X Sulfate) and 2 (1X Intellibond) contained 1,000, 2,000, and 3,000 mg/kg DM of Cu, Mn, and Zn, respectively. While treatment 3 (0.5X Intellibond) contained 500, 1,000, and 1,500 mg/kg DM of Cu, Mn, and Zn. All free-choice mineral supplements were formulated to provide 0.15% supplemental S, 15 mg/kg Co from Co carbonate, and 55 mg/kg I from Ca iodate (Hubbard Feeds; Mankato, MN). Supplement consumption was formulated for 113 g·animal-1 ·d-1. Supplement intakes were determined every 28 d. Liver biopsies and blood samples were obtained before the experiment was initiated (d -45), after calving (d 158 and 159), and after weaning (d 294) at the end of the first production year. Each replicate was rotated to a different pasture every 2 to 4 weeks to minimize pasture effects. Cows were weighed during each liver biopsy event and at each scheduled handling events. A two-day calf weaning weight was collected during weaning (d 260 and 261). Over the first year of the experiment, cow BW, BCS, mineral status, mineral intake, and calf weaning weight were collected. There was no impact of treatment on any of the response variables measured during the first year of the experiment.
  • ItemOpen Access
    Impact of low-level tannin supplementation on enteric methane emissions, estimated nitrogen excretion, oxidative stress, and animal performance in organic dairy heifers
    (Colorado State University. Libraries, 2023) Schilling, Ashley, author; Stackhouse-Lawson, Kim, advisor; Place, Sara, committee member; Pinedo, Pablo, committee member; Velez, Juan, committee member; Moore-Foster, Rhyannon, committee member
    Heightened attention and concern regarding the role of anthropogenic greenhouse gas (GHG) emissions in climate change has challenged every industry to reduce their environmental impact. In cattle production systems, the importance of feeding the growing human population while minimizing environmental impacts has been given significant attention throughout the 21st century (Steinfeld et al. 2006; Golub et al., 2012; Eisler et al. 2014). In 2020, the United States dairy industry was responsible for approximately 1.4% of total anthropogenic GHG emissions (EPA, 2021). The GHGs with the largest global warming potential (GWP) equivalents in dairy cattle production systems are nitrous oxide (N2O) and methane (CH4) (Rotz et al., 2021). The use of tannins as a feed additive in cattle production systems has been explored as a GHG mitigation strategy given their potential to reduce enteric CH4 and reactive-nitrogen (N) emissions, while also benefiting animal health. Tannins are secondary components of plants comprised of phenolic compounds of diverse molecular weights and of variable complexity (Place et al., 2011). They are classified into two major classes: 1) hydrolysable and 2) condensed tannins and exhibit variable affects depending on their class, concentration/purity, dose, type, and other factors such as animal species, animal physiological state, and diet composition (Makkar 2003; Aboagye and Beauchemin, 2019). When fed to ruminants, such as dairy cattle (Bos taurus), tannins act as rumen modifiers by altering protein and carbohydrate degradation in the rumen. Moreover, tannins have demonstrated anti-microbial, anti-parasitic, antioxidant, anti-inflammatory, and anti-viral effects in animals and the ability to serve as a bloat control mechanism (Mangan, 1988; Jones et al., 1971, Min et al., 2005). Since tannins target rumen microbial populations that assist in fiber degradation, unintended consequences can include reductions in feed intake, digestibility, and rate of BW gain when tannins are supplemented at concentrations greater than 55 g condensed tannins/kg dry matter (DM) (Min et al., 2003). Therefore, the objective of this study was to determine the impact of low-level tannin (< 0.30 g/kg DMI) supplementation on enteric CH4 emissions, estimated N excretion, oxidative stress, and performance in organic Holstein heifers. Heifers (n=20) were supplemented with Silvafeed® ByPro, a Schinopsis lorentzii condensed tannin product, at increasing levels as recommended by the manufacturer: 0% (CON), 0.075% (LOW), 0.15% (MED), and 0.30% (HIG) of dry matter intake (DMI). Based on animal success to a 28 d acclimation period, 20 certified organic Holstein heifers (BW = 219 ± 17 kg) were randomly assigned into one of the four treatment groups and stratified based on initial body weight (i.e., a completely randomized design). A 7 d pretrial gas analysis was performed prior to study initiation to account for individual animal emission differences. Daily, heifers were supplemented with one kg of sweet feed and tannin in accordance with the assigned treatment in individual feeding stanchions for 45 d and fed a basal total mixed ration (TMR) diet through four SmartFeed Pro intake measurement bunk systems (C-Lock Inc., Rapid City, SD) which allowed for measurement of individual animal feed intake. Additionally, CH4 and carbon dioxide (CO2) production was measured using one GreenFeed automated head chamber system (AHCS, C-Lock Inc., Rapid City, SD) for the entirety of the study. Statistical analysis was conducted in R© (R Core Team, 2021, v. 4.1.2). Data were analyzed as a completely randomized design with animal (n=20) as the experimental unit, using the Type III ANOVA procedure. Post-hoc pairwise comparisons for dependent variables by treatment were performed using the least squared means procedure with the Tukey HSD adjustment applied. Daily CH4 production ranged from 136.5 to 140.1 g CH4/hd/d between treatments. No significant difference was observed between treatments for daily CH4 production (P=0.95), CO2 production (P=0.95), CH4 as a percent of gross energy (GE) intake (Ym; P=0.87), CH4 yield (MY; g CH4/kg DMI; P=0.80), and CH4 emission intensity (EI; g CH4/kg of BW gain; P=0.70). Similarly, a treatment effect was not observed for DMI (kg/d; P=0.92), average daily gain (ADG; kg BW gain/d; P=0.53), or feed efficiency (G:F; kg of BW gain/kg of DMI; P=0.42). Nitrogen intake ranged from 195 to 214 g/d among treatments (P=0.93). No significant difference was observed among treatments for fecal output (P=0.98), fecal N (FN; P=0.98), fecal neutral detergent fiber (NDF; P=0.33), or fecal acid detergent fiber (ADF; P=0.30). Estimated urine nitrogen (UN) (P=0.77), FN:UN (P=0.93), and N excretion (P=0.86) did not differ among treatments when estimated using methodologies described by Kohn (2005) (Table 5). Similarly, estimated UN (P=0.66), FN:UN (P=0.94), and N excretion (P=0.72) did not differ among treatments when estimated using methodologies described by Reed (2015). Moreover, no significant difference was observed among treatments for serum parameters, blood urea nitrogen (BUN; P=0.99) or creatinine (P=0.20), the common oxidative stress biomarker malondialdehyde (MDA; P=0.63), or antioxidant enzyme biomarkers superoxide dismutase (SOD; P=0.26) and reduced glutathione (GSH; P=0.19). Ultimately, the results of this study would not indicate that low-level tannin supplementation alters CH4 emissions, estimated N excretion, oxidative stress, or animal performance in organic dairy heifers.