Theses and Dissertations

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Open Access
Use of video image analyses to identify carcass characteristics and sensory quality of beef products generated from mature cow carcasses
(Colorado State University. Libraries, 2009) Woerner, Dale R., author; Belk, Keith E., advisor; Tatum, J. Daryl, advisor
A single study (sponsored by the beef check-off) was conducted to investigate the ability of video image analysis technology to identify carcass characteristics and sensory attributes of products generated from mature cow carcasses. Market cows representing three pre-harvest management strategies were used to evaluate the ability of video image analysis (VIA) to identify the impacts of pre-harvest management (MGMT) on carcass muscle and beef sensory characteristics. Cow MGMT groups were as follows: (1) Non-fed cows (n = 104) (NON-FED; beef-type cows entering the slaughter facility as culls from sale barns and/or ranching operations); (2) Fed cows (n = 108) (FED; beef-type cows entering the slaughter facility from a finishing yard having received a corn-based, high energy diet for a 95 d ± 1 d period); (3) Dairy cows (n = 113) (DAIRY; cows entering the slaughter facility directly from dairies as culls). FED market cows were fatter, heavier, and more muscular than either NON-FED or DAIRY cows. DAIRY cows were slightly fatter (in the carcass), heavier, and less muscular (alive, muscle score) than were NON-FED beef cows. FED beef cows had the most desirable lean color scores, the most tender LM steaks, and had whiter colored fat than NON-FED beef cows. DAIRY cows were the most youthful (lowest SKELMAT and dentition scores) at the time of harvest and produced carcasses that had similar marbling and fat color scores to those of FED beef cow carcasses. NON-FED beef cows produced the lowest marbling scores, the toughest LM steaks, and the most yellow colored fat. Correspondingly, fat from NON-FED beef cows had the highest concentrations of vitamin A and 3-carotene in the fat. NON-FED cows had the greatest probability of producing beef with undesirable flavor attributes but no meaningful differences were found among MGMT groups in fatty acid composition. Cow LM representing all MGMT groups responded to postmortem muscle-aging (P < 0.001) whereas the PM did not (P = 0.075). A MGMT x postmortem muscle aging time interaction existed for the INFRA (P < 0.042). A significant interaction of MGMT x evaluation method (USDA grader vs. VIA instrument) existed for marbling score, LMA, and 12th rib fat thickness. Compared to USDA grader determined values, VIA instrument scores were higher for marbling score and lower for LMA. A prediction model developed from VIA instrument outputs demonstrated the ability to characterize the MGMT of cow with less than 13% error. The findings of this research warrant the continued development VIA instruments to identify cow carcass characteristics and sensory quality.
Open Access
Application of yeast technology in ruminant nutrition
(Colorado State University. Libraries, 2009) Swyers, Kelcey L., author; Archibeque, Shawn L., advisor
This research aimed to evaluate two types of yeast technology applications that are commercially available to feed in the diets of beef cattle; these two applications are dried distiller's grains with solubles (DDGS) and yeast culture (YC). First, DDGS were offered as a protein and energy supplement to pregnant range cows to evaluate performance, and nitrogen and trace mineral status of cows and calves (Exp. 1), then YC was fed as a natural alternative to an ionophore to heavy-weight yearling beef steers fed finishing diets consisting of 19.7% DDGS to evaluate growth performance, carcass merit, cost of gain (COG) (Exp. 2), and fecal prevalence of the foodborne pathogen, E. coli O157:H7 (Exp. 3). In Exp. 1, supplementing the diets of pregnant beef cows maintained on dormant winter range with DDGS improved cow performance, had limited impact on nitrogen or mineral status, and was more economical to feed than the control diet (standard range cubes). In Exp. 2, we found that feeding YC may improve carcass characteristics of steers finished at lower end weights, which could result in fewer days on feed; however, there was no advantage on growth performance or COG. Lastly, Exp. 3 indicated that feeding YC decreased, but did not eliminate, fecal shedding of E. coli O157:H7 upon initial application.
Open Access
Prevalence and control of Listeria, Salmonella and Escherichia coli O157:H7 in Colorado rural households
(Colorado State University. Libraries, 2009) Rodríguez Marval, Mawill R., author; Belk, Keith, advisor; Sofos, John, advisor
The household environment has been linked to multiple outbreaks of foodborne illnesses, including listeriosis and salmonellosis. The food handling habits of consumers play a critical role in the food chain continuum, and need to be investigated to better prevent foodborne illnesses that originate at home. The objective of this work was to identify risk factors associated with prevalence of Listeria, Salmonella and Escherichia coli 0157:H7 in the rural household environment, and to provide scientific data for the development of reheating instructions for frankfurters in the home setting. To study risk factors associated with Listeria, Salmonella and Escherichia coli 0157:H7 prevalence in rural Colorado households with or without ruminants, households were recruited, and samples from food and the environment, as well as behavioral data from the primary foods preparer in the house, were collected. Listeria was isolated from refrigerators, kitchen sinks, shoes soles, clothes washing machine and food samples, with higher prevalence in households with ruminants. No sample was found positive for E. coli 0157:H7, and Salmonella was isolated from one refrigerator, one washing machine, one working glove, and two shoe samples. Results indicated that behavior related to handling and cooking of perishable foods affected the probability of household samples testing positive tor Listeria, regardless of presence of ruminants. Personal cleanliness habits were related to presence of Listeria on shoe soles, clothes washing machine, and working gloves. Shoes testing positive in households with ruminants were more frequently associated with multiple positive environmental samples compared to households without ruminants. Results indicated that consumer education on handling and storing perishable foods, and animal handling to prevent contamination of the household through shoes or clothes may reduce prevalence of Listeria in home environments. Two studies evaluated reheating of frankfurters inoculated with L. monocytogenes with or without antimicrobials. In both cases, frankfurters were formulated with or without 1.5% potassium lactate and 0.1% sodium diacetate and were inoculated with a ten-strain composite of L. monocytogenes. After inoculation, frankfurters were vacuum packaged and stored under conditions simulating manufacturing/retail and consumer storage. In one study, after the appropriate storage time, frankfurters were placed in a bowl with water and treated in a household microwave oven. Exposure to high power for 75 s reduced pathogen levels (0.7±0.0 to 1.0±0.1 log CFU/cm2) to below the detection limit (<-0.4 log CFU/cm2) on frankfurters with actate/diacetate. On frankfurters without lactate/diacetate, initial levels of L. monocytogenes (1.5±0.1 to 7.2±0.5 log CFU/cm2) on untreated samples increased as storage in vacuum and aerobic packages progressed. For this formulation, the exposure to high power for 75 s produced reductions between >1.5 and 5.9 log CFU/cm2. Depending on the treatment and storage time, the water used to reheat the frankfurters had viable L. monocytogenes counts of <-2.4 to 5.5±0.5 log CFU/ml. Results indicated that levels of L. monocytogenes contamination <3.7 log CFU/cm2, on frankfurters can be significantly (P>0.05) reduced by microwave oven heating at high power for at least 75 s. Higher contamination levels, such as those found on frankfurters without lactate/diacetate and stored for a prolonged period of time, require longer exposure to microwave heating in order to render the product safe for consumption. In the other study, inoculated frankfurters were treated with hot water after different storage periods to evaluate the destructiveness of different time and water-temperature combinations L. monocytogenes. Treatments at 80°C (60, 120 s) and 94°C (30, 60 s) reduced pathogen counts on frankfurters with PL/SD to at/below the detection limit (<-0.4 log CFU/cm) from initial levels on control (immersed in 25°C water for 300 s) samples. For frankfurters without PL/SD, where pathogen numbers reached 6.1 log CFU/cm2 on 60-day old vacuum-packaged product stored aerobically for 7 days, hot water treatments reduced counts by 1.0 (30 s/80°C) to >6.0 (120 s/94°C and 300 s/94°C) log CFU/cmz. No survivors were detected in the heated water after any treatment (detection limit <-2.5 log CFU/ml). While low levels of L. monocytogenes on frankfurters can be inactivated with short exposure to hot water, increased contamination that may occur as the product ages needs longer times and/or higher temperature for inactivation.
Open Access
Effects of pre-slaughter cattle management on postmortem tenderization of beef
(Colorado State University. Libraries, 2009) Gruber, L. Sandra, author; Tatum, J. Daryl, advisor
Two independent studies were used to investigate the effects of pre-slaughter cattle management on postmortem tenderization of beef. In experiment I, relationships between behavioral and physiological symptoms of pre-slaughter stress and beef LM tenderness were examined using calf-fed steers (n = 79) and heifers (n = 77). Pen, chute, and post-transportation behavior scores were assigned to each animal. Physiological indicators of stress included cortisol, epinephrine, creatine kinase, lactate, glucose, heart rate, respiration rate, and rectal temperature. Positive correlations (P < 0.05) between behavior scores and physiological parameters indicated that cattle that exhibited behavioral symptoms of stress also responded physiologically. Mean Warner-Bratzler shear force (WBSF) was positively correlated (P < 0.05) with all 3 measures of stressful behavior (r ≥ 0.23). Plasma lactate concentration at slaughter was associated (P < 0.05) with mean WBSF and response to postmortem aging. In Experiment II, effects of genotype and implant program on LM and gluteus muscle (GM) postmortem tenderization were investigated using crossbred steer (n = 185) and heifer (n = 158) calves. The 3-marker GeneSTAR Tenderness panel was used to determine each animal's genotype. Calves were assigned to 1 of 2 implant programs, conventional or delayed. Steaks from conventionally implanted cattle had WBSF values that were approximately 0.2 kg higher (P < 0.05) than steaks from animals that received a single delayed implant, but only during the early postmortem period (3 to 7 d). For both muscles, a linear effect of genotype on WBSF was detected (P < 0.05). Steaks from cattle with most desirable genotype had WBSF values 0.33 kg lower than steaks from cattle with the least desirable genotype. Pre-slaughter factors (sex, implant program, and genotype) controlled in Experiment II each accounted for less than 10% of the explained variation in tenderness of the experimental population. Results of Experiment I identified behavioral and physiological symptoms of acute pre-slaughter stress that were associated with pH-independent differences in tenderness. Findings from Experiment II suggest that pre-slaughter cattle management can impact beef tenderness, but the factors evaluated only accounted for a small proportion of variation in beef tenderness for the experimental population.
Open Access
Survey of husbandry, management, housing, leg lesions, hygiene, production, economics, and cow behavior, on 113 commercial U.S. dairies
(Colorado State University. Libraries, 2007) Fulwider, Wendy K., author; Grandin, Temple, advisor
Dairy cattle should be kept clean, dry and comfortable. There are economic and welfare advantages for providing housing for dairy cows during the winter months instead of leaving them outside in harsh climates. To improve overall health and well-being, cows should be moved from indoor stalls into the barnyard, where they can groom themselves and one another. Cows should be able to stretch, sun themselves, exhibit estrus behavior, and exercise. To decrease the incidence of leg problems, mastitis, bloat, and calving-related disorders cows should be allowed generous access to outdoor pastures or exercise yards. In the first essay, dairy cow behavior, needs, and preferences for housing and milking centers is discussed. Current recommendations for stall size and management practices are reviewed. The social needs of dairy cattle and the benefits of positive human-animal interactions were reported. Recommendations for transport were also included. In the second essay, dairy cow hygiene, leg lesion incidence and location for cows on 113 dairies were recorded and analyzed. Stall bed types reviewed included compost pack, rubber filled mattresses, sand, and waterbeds. Results indicated that stall bed type was a good predictor for leg lesion incidence and location of wound, as well as level of hygiene. The numbers of mature cows present on a dairy were also related to bed type, as well as bed length in sand stalls. Severe lesions were associated with higher somatic cell counts. There were correlations between high somatic cell counts and the percentage of cows reported lame by the producer and the neck rail height. High leg lesion rates were correlated with somatic cell count, death loss, and percentage of herd reported lame. The third essay evaluates diiferent stall bed types for culling rate, percentage of mature cows in herd, bedding cost and frequency. Producer satisfaction for cow comfort, manure management, and cow longevity, by base type were reported. This data indicated that waterbeds were a viable option for cows and producers when good quality sand is unavailable or handling sand-laden manure is not feasible.
Open Access
Heifer pregnancy genetic prediction and simulation modeling techniques
(Colorado State University. Libraries, 2008) Comstock, Carlton R., author; Enns, R. Mark, advisor; Bourdon, Richard M., advisor
The Colorado Beef Cattle Production Model (CBCPM) was rewritten with an object oriented design and used to simulate heifer pregnancy data with varying levels of age at puberty (AAP), probability of conception (PCON), and length of breeding season. Five percent of the heifers were simulated infertile due to non-genetic causes. Simulated data were used to estimate heritability of heifer pregnancy and to obtain EBV using threshold models. The EBV were tested for accuracy of prediction of the simulated genetic fertility traits. Object oriented methods used illustrated the ability of these techniques and tools, such as Unified Modeling Language, at organizing complex processes in ways to reduce errors and code maintenance effort, and to facilitate collaboration among developers. Adoption of these tools will be critical to the advancement of systems models. Heritability of heifer pregnancy from 20,000 heifers with very early puberty in the first 25 d of the breeding season was .139, .107, and .143 for mean PCON of 60, 70, and 80%, respectively, close to the .10 input heritability of PCON. The higher estimates may be due to a few heifers having two opportunities to breed. With very late puberty and 80% mean PCON in a 25 d breeding season the heritability estimate of AAP was .337, lower than the simulated .40 heritability. The estimate was lower because there was not 100% conception, some heifers were infertile, and puberty was observed as a threshold trait. Heritability estimates of heifer pregnancy generally decreased as breeding season length increased, likely due to an increasing percent of open infertile heifers. The ability of the variance component estimation software to converge on an estimate decreased as the number of open, fertile heifers decreased. The most difficulty was with high PCON, early puberty, and long breeding seasons; only one out of 100 estimates converged at 340 d AAP, 80% PCON, and 120 d breeding season. Calculated accuracy for heifer pregnancy EBV for the sires of the heifers using prediction error variances from a linear model, with the binary pregnancy observations treated as continuous data, overestimated accuracy of the EBV with respect to the simulated traits in all cases. Calculated accuracy was insensitive to changes in frequency of heifer pregnancy observations. Accuracy calculated as the simple correlation of the EBV with each simulated fertility trait for the sires of the heifers was highest in most cases at the shortest breeding season. The correlation with AAP was essentially zero for early puberty, and strongest (-.775) at late puberty. As breeding season length increased the AAP correlation declined toward zero. The accuracy for PCON was less sensitive to changes in AAP and breeding season length, ranging from .146 to .753; the strongest correlations were with early puberty and low PCON.
Open Access
Ecology and persistence of Escherichia coli O157:H7 in feedlot cattle and characterization of molecular mechanisms responsible for attachment
(Colorado State University. Libraries, 2009) Carlson, Brandon Adolph, author; Belk, Keith E., advisor
Studies were conducted to elucidate the shedding dynamics and ecology of Escherichia coli O157:H7 in feedlot cattle. Feedlot cattle (N=788) were evaluated for E. coli O157:H7 shedding six times during the final 120 d of finishing. Fecal samples were analyzed for E. coli O157:H7 with IMS and confirmed with multiplex PCR. During the first two collections, where all 788 steers were samples, 39.8 and 33.6% of steers were shedding an E. coli O157:H7 isolate possessing eae, stxI, and stxII. Through subsequent sampling, 1% of steers were characterized as persistent E. coli O157:H7 shedders (PS) where as 1.4% of steers were never shedding a detectable amount of the organism. Molecular characterization of E. coli O157:H7 isolates obtained from PS (n=80) and transient E. coli O157:H7 shedders (n=52) revealed a diverse but closely related population of isolates and identified a predominant subtype that accounted for 53% of the isolates characterized that was not dependent (P > 0.05) on animal shedding status. Pathogenic potential of E. coli O157:H7 isolates representing different subtypes was delineated with a Caco-2 cell (intestinal epithelial cell line) attachment assay. There was an inverse relationship (P < 0.05) between genetic diversity and attachment efficacy; as diversity from the dominant subtype increased, ability to attach to Caco-2 cells diminished. Additional attachment assays were initiated to evaluate the influence of virulence genes upon E. coli O157's ability to attach to Caco-2 cells. E. coli O157 isolates without either stx, no stxI, and no stxII genes resulted in attachment abilities of 76.7, 65.5 and 57.7%, respectively; all of which were greater (P < 0.05) than an E. coli O157:H7 that was isolated from a food implicated in human disease and possessed both stx genes. Cytotoxicity assays were utilized to verify that differences in attachment efficacy, exhibited by E. coli O157 isolates of various virulence genotypes, were independent of cellular destruction.
Open Access
Effects of brining ingredients and antimicrobials on thermal inactivation of Escherichia coli O157:H7 in a meat model system and control of Listeria monocytogenes in frankfurters
(Colorado State University. Libraries, 2009) Byelashov, Oleksandr Anatolievich, author; Sofos, John N., advisor
Microbial food safety has been one of the most important challenges for the meat industry and regulatory agencies during the last two decades owing to outbreaks by pathogens such as Escherichia coli 0157:H7 and Listeria monocytogenes traced tocontaminated products, and associated with costly product recalls from the market. Among others, E. coli 0157:H7 infections have been associated with undercooked contaminated brine-injected meats. L. monocytogenes is of particular concern in ready-to-eat (RTE) meat and poultry products.
Open Access
Effects of endocrine modifiers on growth, carcass characteristics, and blood and tissue metabolites of finishing beef cattle
(Colorado State University. Libraries, 2008) Bryant, Anthony C., author; Engle, Terry E., advisor
The effects of vitamin A and the interaction of steroids and beta-adrenergic agonists on growth and carcass performance, tissue metabolite profiles, and lipogenic enzyme activity were evaluated in beef cattle. In 1 experiment steers were fed 1 of 5 supplemental levels of vitamin A (0, 1,103, 2,205, 4,410, or 8,820 IU/kg DM). Final BW, G:F, ADG, HCW, LM area, marbling, and quality grade distribution did not differ among treatments. Except for d 56, no correlations between marbling score and tissue retinol concentrations or vitamin A intake were found. A negative correlation between liver retinol and α-tocopherol was observed, which may have potential health implications. Results suggest that vitamin A supplementation up to twice the NRC-suggested concentration has little effect on performance, marbling, or lipogenic enzyme activity in yearling steers and further suggest that 2,205 IU supplemental vitamin A/kg of DM is adequate for growing/finishing beef steers.
Open Access
Determination of antibiotic, ß-agonist, and non-steroidal anti-inflammatory drug residues in ground beef from USDA certified organic, natural, conventional, and market cow and bull sources
(Colorado State University. Libraries, 2009) Bowling, Mitchell Brett, author; Belk, Keith, advisor
In recent years, consumer demand for organic and "natural" products has increased, partly due to a perception that such products are healthier and contain fewer additives, including veterinary drugs and growth promotants. The study presented herein compared occurrence of veterinary drug residues in ground beef samples reflecting different livestock production classifications. We collected ground beef samples (N = 400) consisting of 90.0 ± 4.0% lean muscle tissue from a total of eight plants, two each reflecting production in the following categories: (1) USDA Certified Organic (n = 100); (2) USDA Process Verified Never Ever 3 (n =1 00); (3) conventionally raised fed beef (n = 100); and (4) ground beef derived from carcasses of market cows and bulls (n = 100). Liquid chromatography coupled with triple-quadrupole mass spectrometry (UPLC-MS) methods were developed for the following veterinary drugs: (1) Aminoglycosides (Gentamicin, Amikacin, and Neomycin); (2) ß-lactams (Penicillin, Ampicillin, and Desfuroylceftiofur); (3) Fluoroquinolones (Danofloxacin and Ciprofloxacin); (4) Macrolides (Erythromycin, Tylosin, and Tilmicosin); (5) Phenicols (Florfenicol); (6) Sulfonamides (Sulfamethazine and Sulfadimethoxine,); (7) Tetracyclines (Oxytetracycline, Chlortetracycline, and Tetracycline); (8) Streptogramins (Virginiamycin); (9) ß-agonists (Ractopamine and Zilpaterol); and (10) non-steroidal anti-inflammatory drugs (Flunixin and Phenylbutazone). Residues exceeding their respective US tolerance limit were found in six ground beef samples. Two USDA Certified Organic samples contained Ampicillin residues exceeding US tolerance limits. One USDA Process Verified Never Ever 3 sample contained a residue of Ractopamine exceeding US tolerance limits. One sample from the market cow and bull category contained a residue of Sulfadimethoxine that exceeded US tolerance limits, one contained a residue of Ampicillin that exceeded US tolerance limits, and one contained a residue of Phenylbutazone that exceeded US tolerance limits. Residues of Phenylbutazone exceeding US tolerance limits were also found in one sample from the conventional production category. Additionally, residues (below the US tolerance limit) of several classes of veterinary drugs were found in samples from the USDA Certified Organic and USDA Process Verified Never Ever 3 production categories, a finding that clearly demonstrates violation of zero-tolerance statutes set forth by the National Organic Program and USDA Process Verified Never Ever 3 marketing descriptors. In the USDA Certified Organic production category, residues were detected in eight Ampicillin, seven Penicillin, three Sulfamethazine, one Sulfadimethoxine, and one Ractopamine sample. In the USDA Process Verified Never Ever 3 production category, residues were detected in one Ampicillin, one Chlortetracycline, two Tetracycline, and six Ractopamine samples. These violations exceed the historical prevalence of veterinary drug residues reported by the National Residue Program and demonstrate the need for careful monitoring of animals administered veterinary drugs in order to prevent improper inclusion of unqualified animals in premium marketing programs, such as USDA Certified Organic and USDA Process Verified Never Ever 3 programs.
Open Access
Fate of Listeria monocytogenes on ready-to-eat meat products, treated with antimicrobials, and under conditions simulating passage through the human stomach and small intestine
(Colorado State University. Libraries, 2008) Barmpalia-Davis, Ioanna Maria, author; Sofos, John, advisor
To cause infection, the foodborne pathogen Listeria monocytogenes must overcome stresses associated with food processing, storage, and preparation, as well as various defense elements of the human body. In this work, we examined factors that may affect growth and survival properties of this pathogen on foods and during passage through a simulated stomach and small intestine.
Open Access
Pre-harvest and postmortem methods of decreasing the incidence and salvaging value of non-conforming beef carcasses
(Colorado State University. Libraries, 2009) Bass, Phillip Dean, author; Belk, Keith, advisor; Scanga, John, advisor
It has been stated that the number of non-conforming carcasses in the beef industry cost the industry millions of dollars yearly in lost revenue. The objectives of this research were to identify muscles in dark-cutting beef carcasses that were not affected by the dark-cutting condition, identify relationships between the portion size of individual muscles in the beef carcass and the carcass ribeye area, and finally to investigate the effects of dietary magnesium (Mg) supplementation on the quality characteristics of beef cattle subjected to stress-inducing environments. Carcasses in the dark cutter study were divided into three classes; 1/3, 1/2, and full degree of dark cutting (DEGDC). The ultimate pH of individual muscles within the carcasses resulted in 7, 9, and 5 muscles having mean pH values considered normal for 1/3, 1/2, and full DEGDC carcasses, respectively. A nation wide survey was conducted to identify the acceptable color range of fresh beef muscles for food service chefs and retail meat merchandisers. Muscles that were within an acceptable color value range for food service chefs and retail meat merchandiser had the potential to add up to $42.29 and $30.30 per side when valued at Choice prices compared to commodity discounted prices, respectively. The portion size study evaluated 14 muscles. Seven of the 14 muscles were found to have no relationship between individual muscle portion size and ribeye area. A nationwide survey was conducted with foodservice chefs and retail meat merchandisers to evaluate the acceptability of portion sizes from carcasses varying in ribeye area size. Results of the survey demonstrated that the portion size of many muscles were still acceptable to retail meat merchandisers and foodservice chefs even though the ribeye area of a carcass may be non-conforming. The study involving the Mg supplementation to beef cattle (N = 144) indicated that the Mg was taken up in the blood stream of the cattle fed the supplement, but no effect on tenderness or reduction of quality defects (e.g., dark cutting) were observed. The results of these studies demonstrate methods of returning value to non-conforming beef carcasses, however, other methods of preventing non-conformity are necessary to research.
Embargo
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.
Open 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.
Open 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.
Open 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.
Open 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.
Open 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.
Open 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.
Open 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.