Theses and Dissertations

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Open Access
Management and benchmarking strategies to improve financial health status of U.S. beef operators
(Colorado State University. Libraries, 2024) Krehbiel, Bethany Cornwell, author; Rhoades, Ryan D., advisor; Ahola, Jason K., advisor; Blackburn, Harvey D., committee member; Mooney, Daniel, committee member
The objective of this dissertation was to obtain, analyze, and summarize historical Standardized Performance Analysis (SPA) benchmark information and subsequently determine significant Key Performance Indicators (KPI) influencing beef producer's Unit Cost of Production (UCOP). Using the KPI's, a Ranch Health Index (RHI) was developed to assist producers in simply analyzing their financial health while analyzing beef production and financial relationships. Lastly, producer information using the significant KPI's incorporated into the RHI was analyzed for sensitivity to explore potential leverage points to enhance overall financial health. The SPA Beef cattle production performance and financial data was obtained from the SPA program conducted by Texas A&M AgriLife Extension which has records from three states: Oklahoma, Texas, and New Mexico. The dataset contained 25 years of beef financial and production metrics from 1992 – 2016. Three models (linear regression, random forest, and step-wise) were used to assess the SPA data for KPI. Upon further analyses, six variables were considered most impactful to predict Unit Cost of Production: Financial Grazing per CWT, Financial Raised/Purchased Feed per CWT, Livestock Cost Basis per CWT, Weaning Pay Weight per CWT, Pounds Weaned, and Number of Adjusted Exposed Females. The RHI was developed from the six variables using a Random Forest machine learning model and their corresponding importance factors as weights in the model. The model selected was tested and showed concordance with all the SPA variables predicting UCOP. Therefore, the RHI results showed utility in usefulness to assess financial health. Subsequently, three producers with 5 consecutive years of data were tested for sensitivity at ± 5% and ± 10% from the original value to determine sensitivity of each KPI variable. Finally, the models were investigated for maximum and minimum RHI values. Results showed changes in RHI up to $13,000 when accounting for all KPI improvements at 10% sensitivity. In conclusion, knowledge of the SPA data and ultimately the RHI provides information to cattle producers on what may be the most indicative variables for enhanced profits. In addition, this research has provided a simple and effective way for producers to analyze their beef operation.
Open Access
Pre-weaning performance in lambs after nutrient specific restriction in gestation and training cognitive skills to improve integration and application of knowledge in animal physiology
(Colorado State University. Libraries, 2024) Stucke, Rachael, author; Cadaret, Caitlin N., advisor; Ahola, Jason K., committee member; Winger, Quinton A., committee member
Due to seasonal availability and quality of range forage, extensively managed ewes often experience nutrient restriction during gestation. Neonatal lamb performance after severe experimental nutrient restriction during gestation has been well studied; however, there is a gap in understanding of how practical nutrient restriction experienced over the course of a production cycle impacts lamb success. Therefore, the objective of the first study was to investigate early life performance in lambs from ewes fed a diet from 30-125 days of gestation (dGA) that simulates winter forage or one that meets all nutritional requirements for gestation. Maternal BCS and weight losses were evident prior to the standard supplementation period suggesting impacts on the fetus could be happening due to nutrient restriction earlier in gestation. Lambs from dams who received the lower quality diet did not differ by bodyweight but were not able to thermoregulate as well as lambs whose dams had their requirements met during the first week and on specific weeks thereafter. Beginning at six weeks of life through weaning lambs from restricted dams had lower body weights compared to lambs from fully nourished dams. This data demonstrates that nutrient challenge during gestation, even when re-alimented in late gestation, decreases performance. The lamb data showed that while there are no apparent differences in growth during the first week of life, NR animals start to diverge later in life even when provided high quality nutrition. This coupled with reduced thermoregulatory ability suggests tissue specific differences may underlie animal variation and warrants further investigation. Case-based learning immerses students in real-world scenarios, prompting observation, action, and reflection to enhance cognitive skills. The open-ended nature of such learning can challenge students to reach higher levels of critical thinking, however, we have noticed that without guidance, students often do not know how to approach these types of questions. Therefore, the objective of study 2 was to investigate how two low-input interventions strategies may help train cognitive skills and improve student performance. Three semesters of an undergraduate physiology course employed a case-based assessment strategy. Semester 1 (S1) represented no intervention, Semester 2 (S2) included two dedicated class periods of instructor-led guidance on approaching case studies, and Semester 3 (S3) utilized an online peer evaluation platform, where students evaluated and provided feedback to each other. In S2 and S3 pre-surveys were administered to understand changes in students' perceptions of their own cognitive skills. The average grade on case studies after intervention was the highest in S3 where peer intervention was employed. When comparing changes in perceptions, student confidence in their cognitive skills generally increased in S2 and S3. Interestingly, while peer evaluation improved student performance, free response questions indicated that students did not enjoy peer evaluation and felt that it was not beneficial to their learning. Peer evaluation provides a unique opportunity for students to actively engage in the learning process and to practice cognitive skills. This process holds dual benefit as reviewing peers requires students to reflect, analyze, and evaluate, which are cognitive skills also needed to solve the case studies.
Open Access
Association between beef ribeye area measurements and steak portion size
(Colorado State University. Libraries, 2024) Schiefelbein, Abbey Faith, author; Nair, Mahesh N., advisor; Geornaras, Ifigenia, committee member; Clark, Daniel, committee member; Hess, Ann, committee member
As cattle weights have increased over the past decades, hot carcass weight and ribeye area (REA) have also increased. The REA is an important determinant of carcass value as it impacts the thickness of steaks when portioned to a pre-determined weight. Additionally, previous research has indicated that steak thickness impacts consumers' eating experience potentially due to its impact on the degree of doneness. The objective of this study was to examine the relationship between carcass REA and steak portion size. Beef carcasses (n = 100) were selected from a commercial beef harvesting facility based on REA in 1 in2 (6.45 cm2) increments ranging from less than 11 in2 (70.97 cm2) to greater than 19 in2 (122.58 cm2) based on a United States Department of Agriculture-approved camera (E+V) with 10 total categories. Data (hot carcass weight, back fat thickness, and marbling) were collected from each selected carcass. The REA measurements were obtained using the grading camera, a manual grid, and pen tracing and measured using ImageJ software. Strip loins (IMPS#180) from selected carcasses were collected, and weight, length, and three width (anterior, middle, and posterior) measurements of the strip loins were measured manually. Each strip loin was then scanned through a Marel I-Cut 56 portion cutter to determine the thickness of 12 oz (340.19 g) and 16 oz (453.59 g) portions and to determine the weight of a 1-in (2.54 cm) thick portion. To quantify and describe the relationship between steak thickness (cut to 12 oz and 16 oz portions) and steak weight (cut at 1-in. thickness), linear regression models were developed using traced REA as the independent variable. Additionally, more exhaustive linear regression models were developed to predict steak thickness or weight based on the traced REA, hot carcass weight, fat thickness, strip loin weight, strip loin length, strip loin width, and average maximum height of the strip loin. Each model was evaluated separately for the main effects of each variable, with significance determined at ɑ=0.05. There was a significant (P < 0.001) correlation and linear relationship (P < 0.05) between traced REA measurement and 12 oz (R2 = 0.71), 16 oz (R2 = 0.71), and 1-in.-thick (R2 = 0.75) portions examined in this study. For 12 oz steaks, the steak thickness decreased by an estimated 0.055 in. (0.14 cm) for every 1-in. increase in REA. Similarly, for the 16 oz steaks, the steak thickness decreased by an estimated 0.074 in. (0.19 cm) for every square in. increase in REA. The 1-in. steak portions had a mean weight of 340 g, and the steak weight increased an estimated 18 g for each square in. increase in REA. In addition, using the strip loin measurements, linear regression models were able to predict steak thickness for 12 oz and 16 oz portions with an R2 of 0.95 each and predict the steak weight for the 1-in. portion with an R2 of 0.98. As expected, REA strongly correlated with the portion size of strip loin steaks cut to a specified weight or thickness. Additionally, our results indicated that the weight and length of the strip loin were good predictors of steak thickness (for 12 oz and 16 oz portions) or steak weight (for 1-in.-thick portions). Further research exploring consumer acceptance and degree of doneness for steaks with varying thicknesses would provide data to determine REA ranges and targets that would optimize steak portion sizes and consumer acceptability.
Open Access
Effects of origin on enteric greenhouse gas emissions and growth performance
(Colorado State University. Libraries, 2024) Mesa Gandolfo, María Inés, author; Carvalho, Pedro H. V., advisor; Stackhouse-Lawson, Kim R., committee member; Place, Sara E., committee member; Ritten, John P., committee member
Methane (CH4) emissions from cattle across various origins remain inadequately understood, representing a significant knowledge gap for sustainable beef production. This study investigates enteric CH4 emissions from yearling steers of different origins and under different management practices. The experiment was divided into two phases. In Phase 1, steers were managed according to local practices: grazing in Colorado and confined background feeding in Nebraska and Wyoming. In Phase 2, all steers were moved to a common grazing environment in Colorado. Methane emissions were measured using the Automated Head Chamber System (AHCS). During Phase 1, CH4 emissions and growth performance varied significantly among the groups, influenced by diet and management. Nebraska steers had the greatest CH4 production (MP), while Colorado steers had the least, reflecting differences in diet composition and feed intake. However, CH4 intensity (MI) was similar across all groups due to compensatory differences in average daily gain (ADG). In Phase 2, when all steers grazed under the same conditions, Colorado steers exhibited the greatest ADG and MP, indicating better adaptation and suitability to the grazing system than Nebraska and Wyoming steers. Results suggest that enteric CH4 emissions are influenced by cattle's origin and previous management. This highlights the need for context-specific studies to accurately assess the sustainability and greenhouse gas (GHG) mitigation strategies for grazing beef cattle. Further research should address these variations to improve the accuracy of CH4 emissions estimates in different rangeland ecosystems. This study also evaluated different CH4 prediction equations using various statistical approaches (RMSE, R2, Mean and Slope bias, correlation coefficients, and least square differences). Three equations showed potential for predicting CH4 emissions for the steers of the current study: the one by Ellis et al. (2009), the one by Escobar-Bahamondes et al. (2016), and Moraes et al. (2014). Even though the CH4 estimated by these equations was similar to the observed, there is room for improvement in the development of accurate equations to predict cattle enteric CH4 emissions in grazing systems. Lastly, the animals were ranked in both Phases by their MI and MP, and it was evaluated if the animals changed their ranking in Phase 1 when moved to Phase 2. Animals from all origins experienced shifts in their classification categories, indicating the dynamic nature of CH4 across different contexts. However, it was observed that steers from the Wyoming group exhibited the most significant changes in MP classification categories when transitioning from a confinement system with grain-based diets to a grazing system. Based on the current results, the background of the steers may need to be considered when evaluating sustainability goals in beef cattle production systems.
Embargo
Transposable elements and early pregnancy in the horse
(Colorado State University. Libraries, 2024) Southerland, Sierra L., author; Coleman, Stephen, advisor; Bruemmer, Jason, committee member; Fedorka, Carleigh, committee member; Pinedo, Pablo, committee member; Chicco, Adam, committee member
Understanding the molecular events and physiological dynamics in the endometrium during early pregnancy is crucial for improving our understanding of reproductive outcomes in horses. Much of the work investigating early pregnancy in the horse has focused on maternal recognition of pregnancy (MRP). This critical signal, which initiates the pathways and regulatory changes to help make the endometrium receptive to pregnancy, remains elusive in the horse. Transposable elements (TEs), once overlooked components of the genome, have been implicated in regulating gene expression during critical stages of embryo and placental development. The current study investigated the expression of TEs during the early phase of pregnancy post-ovulation. The hypothesis tested was that pregnancy status would impact the expression patterns of TE-derived transcripts in the endometrium around the time of maternal recognition. It was anticipated that the TE transcripts would increase in the endometrium of pregnant mares either in response to or as a part of the maternal recognition signal. RNA sequencing data was generated from endometrial biopsies at days 9, 11, and 13 in pregnant and non-pregnant mares. Bioinformatics analyses identified distinct patterns of TE expression across the duration of early pregnancy. Contrary to expectations, these findings did not reveal the accumulation of TE transcripts in the pregnant endometrium compared to the non-pregnant endometrium during early pregnancy. Instead, there was a significant decrease in the number of differentially expressed transcripts over the time points studied. These results challenge the initial assumption and suggest that the regulation of TE transcriptional activity during early pregnancy may be more complex than previously thought, highlighting the need for further research into the roles of TEs in equine reproductive physiology. An alternative explanation for the results of this analysis is that maternal recognition of pregnancy may involve the downregulation of transcripts expressed from TEs, potentially serving as a switch to prevent luteolysis and maintain pregnancy. This study underscores TEs as potential biomarkers and regulators in equine reproduction, providing insights into endometrial processes and offering avenues for improving fertility outcomes and breeding efficiency in horses.
Open Access
The association of lunar phases with pregnancy at first artificial insemination of dairy cows
(Colorado State University. Libraries, 2024) Schatte, Margaret, author; Grandin, Temple, advisor; Pinedo, Pablo, advisor; Keller, Kayleigh, committee member
Myths and old farming legends have circulated the belief that the full moon affects livestock behavior and reproduction. To assess this association in dairy cattle, 13,558 records from 2019 to 2021 at an organic dairy farm in Colorado were analyzed. These records included lactation number, artificial insemination date (AI date), and pregnancy result. AI date was categorized into season and lunar phases. Lunar phases were separated into four equal categorizations: new moon, first quarter, full moon, and third quarter. The primary objective of this study was to identify any associations between the lunar phases and PAI1 (pregnancy rate at first AI). The secondary objective of this study was to use logistic regression to specify which phases had the lowest and greatest PAI1 while accounting for other effects on fertility. Logistic regression was used to complete this by comparing the pregnancy result of lunar phases while accounting for lactation number and season, which are known to affect pregnancy rate. The 4 lunar phase categorizations did have an association on PAI1 (p<0.05). The new moon phase resulted in the lowest PAI1 at 35.3% while the third quarter was the highest at 38.3%. Estimated marginal means were explored to identify the seasonal effect on pregnancy and found that winter had the highest probability of pregnancy and summer had the lowest. This analysis of 3 years of records provides evidence that the week of the new moon is the least probable week out of the month for pregnancy after first AI to occur, while the week before and week of the full moon are the most probable days for pregnancy after first AI to occur within the lunar cycle.
Open Access
Influence of BOVAMINE DEFEND® Plus on growth performance, carcass characteristics, estimated dry matter digestibility, rumen fermentation characteristics, and immune function in finishing beef steers
(Colorado State University. Libraries, 2024) Miller, Alexandra C., author; Engle, Terry E., advisor; Edwards-Callaway, Lily, committee member; Holt, Timothy, committee member
One hundred and eighty crossbred beef steers (406.0 ± 2.2 kg) were used to determine the impact of a novel direct-fed microbial (DFM) on growth performance, carcass characteristics, rumen fermentation characteristics, and immune response in finishing beef cattle. Steers were blocked by body weight and randomly assigned, within block, to 1 of 2 treatments (3 replicates/treatment: 30 steers/replicate). Treatments included: 1) no DFM (control) and 2) DFM supplementation at 50 mg∙animal-1∙d-1 (BOVAMINE DEFEND® Plus). All steers were fed a high-concentrate finishing diet and individual feed intake was recorded daily via the GrowSafe® system. Body weights were collected every 28 d. On d 55, 10 steers per pen were injected with ovalbumin (OVA). Jugular blood samples were collected from each steer on d 0, 7, 14, and 21 post-injection. On d 112, the same steers were injected again with OVA and intramuscularly with a pig red blood cell solution. Jugular blood samples were collected from each steer on d 0, 7, 14, and 21 post-injection. On d 124 rumen fluid was collected from 3 steers per treatment and used to estimate in vitro rumen fermentation characteristics. Equal numbers of steers per treatment were transported to a commercial abattoir on d 145, 167, and 185 of the experiment, harvested, and carcass data collected. Initial body weight (BW) was similar across treatments. On d 28 and 55, steers receiving DFM had heavier BW (P < 0.01) compared to controls. Average daily gain was greater in DFM-supplemented steers from d 0 to 28 (P < 0.01) and d 0 to 55 (P < 0.01) of the experiment compared to controls. Overall dry matter intake was greater (P < 0.04) and overall feed efficiency was similar in DFM-supplemented steers compared to controls. Dressing percentage (P < 0.02) was greater in steers receiving DFM compared to controls. Antibody titers to injected antigens were similar across treatments. However, red blood cell superoxide dismutase activity was greater (P < 0.05) in DFM-supplemented steers compared to controls. In vitro molar proportions of isobutyric and butyric acid were greater (P < 0.01) and dry matter (DM) digestibility tended (P < 0.07) to be greater in rumen fluid obtained from steers supplemented with DFM. These data suggest that BOVAMINE DEFEND® Plus supplementation improves growth performance during the initial period of the finishing phase, increases overall dry matter intake and dressing percentage, and may impact antioxidant status in beef cattle.
Open Access
Effect of hot-iron brand size and meloxicam on behavior, health, and performance of beef calves in a pasture setting
(Colorado State University. Libraries, 2024) Keogh, Lily, author; Edwards-Callaway, Lily, advisor; Cramer, Catie, advisor; Wolfe, Barb, committee member; Engle, Terry, committee member
Animal welfare is of growing importance in beef cattle production and therefore there is heightened interest in regularly practiced, painful management practices. Hot-iron branding is a common method of permanent identification of cattle, created by intense thermal damage to the hide. The main objectives of the study were to quantify the effects of hot-iron brand size and meloxicam on pain related behaviors and health and performance parameters of 2-month-old beef calves on a commercial cow calf operation. A total of 126 calves were enrolled in the study (bulls, n=56; heifers, n=70). Calves were hot-iron branded with one of two iron sizes (small (SM), large (LG)) and administered meloxicam (MEL; dosed for a 113-kg calf at 1mg/kg of bodyweight) or a placebo (PLA)), and castrated (CAS) or not castrated (NCAS), if a heifer calf. Following the treatment application, behavioral observation (2 h periods) using instantaneous scan sampling occurred at 6 h and 24 h post branding; these observation periods (OP) represent the pharmacokinetics of oral meloxicam. A logistic regression (PROC GLIMIX) was used to assess the association between castration status, brand size, medication, observation period, as well as any interactions, on the proportional behavioral outcomes. More LG brand calves were observed standing, lying, and displaying event behaviors as compared to the SM brand calves (P = 0.003, P = 0.011, P = 0.016, respectively). OP affected the display of event and state behaviors, with standing observed more at 6 h and event behaviors displayed more at 24 h (P = 0.0028). Concurrently, CAS and SM or LG branded calves exhibited more event behaviors and standing than NCAS calves (P = 0.022). No effect of the fixed variables on average daily gain (ADG) or morbidity were observed (P > 0.05). MEL did reduce the proportion of branded heifer calves expressing event behaviors as compared to PLA, however it had less of a behavioral impact on the concurrently castrated and branded calves (P = 0.022). The results indicate that pain is present within the 24 h following branding and castration and that concurrent castration and branding elicits a greater behavioral response than only branding. This study highlighted both the feasibility of administering an oral analgesic in a commercial setting and that implementing a smaller brand size may be a strategy to reduce pain associated with hot-iron branding.
Open Access
Propionibacteriaium acidipropionici CP 88 dose alters in vivo and in vitro ruminal fermentation characteristics
(Colorado State University. Libraries, 2024) Levenson, Jonah, author; Engle, Terry E., advisor; Wagner, John J., committee member; Torres-Henderson, Camille, committee member
Twelve steers, fitted with rumen canulae were used in a 4 x 4 Latin square design to examine the impact of the direct fed microbial Propionibacteria acidipropionici (PA) on rumen fermentation characteristics. All steers were housed together in one pen equipped with GrowSafe feed intake monitoring stations and one Greenfeed system used to estimate in vivo methane production. Steers were fed a corn silage-based diet throughout the experiment. Treatments consisted of PA administered at: 1) 0.0; 2) 1.0 x 108; 3)1.0 x 109; and 4) 1.0 x 1010 CFU∙animal-1∙day-1. Treatments were administered directly into the rumen as a single bolus dose daily. On day 7 and 14 of each period, rumen fluid was collected from each steer 2 h post treatment administration for VFA analysis and for determining in vitro fermentation characteristics. Following a 14-d washout period, animal treatments were switched, and the experiment repeated. Data were analyzed as a 4 x 4 Latin square design. In vivo propionic acid molar proportions (25.4 vs 23.6±0.24 mM) and total VFA concentrations (125.2 vs 121.3±1.87 mM) were greater (P < 0.05) in steers receiving PA when compared to controls. In vitro DM disappearance (P < 0.05; 63.3% vs 59.2%±1.12) and total VFA (P < 0.05; 147.9 vs 145.2±1.76 mM) were greater and methane (ml/g DMD) lesser (P < 0.04; vs 13.1 vs 15.6±0.11) in fermentation vessels incubated with rumen fluid from animals receiving PA when compared to controls. Dry matter disappearance (P < 0.03) and propionic acid (P < 0.04) increased linearly as dose of PA increased. In vitro total VFA tended (P < 0.08) to increase linearly and methane production tended (P < 0.09) to decrease quadratically in response PA dose. In vivo methane production was similar across treatments. In conclusion, PA addition improved in vivo and in vitro rumen fermentation, gas production, and rumen microbial manipulation.
Open Access
Gene expression analysis before and after the pelvic flexure in the equine hindgut
(Colorado State University. Libraries, 2024) Moss, Cameron D., author; Coleman, Stephen J., advisor; Engle, Terry, committee member; Metcalf, Jessica, committee member; Landolt, Gabriele, committee member
The equine hindgut is the primary site of the horse's nutrient breakdown, absorption, and energy production. More than 60% of the horse's energy comes from hindgut fermentation. In this process, commensal microbes in the hindgut aid in the digestion of plant materials to create volatile fatty acids that can be used by host cells to make energy. Many severe health issues- such as colic, laminitis, or colonic impactions- often occur in the equine hindgut, making it an important site to study to provide better management, treatment, and prevention options for horses suffering from gastrointestinal disease. Although much research exists focusing on the microbiome and overall physiology of the equine hindgut, relatively little addresses the role of gene expression in maintaining a complex yet essential homeostatic balance within the gastrointestinal tract. Previous from our lab found major differences in the microbial content of gastrointestinal compartments of the equine hindgut, separated by the pelvic flexure. The pelvic flexure is a short, narrow, horseshoe-shaped loop in the equine large colon. It defines the ventral and dorsal segments of the colon and is a common site of colonic impaction in horses. Although the pelvic flexure cannot and should not act as a "barrier," something "barrier-like" may be occurring around this region as it pertains to the hindgut microbiome. The mechanism for this action is not defined. As a result, this thesis aims to investigate gene expression in the intestinal epithelial cells of the ventral colon, pelvic flexure, and dorsal colon regions of a healthy hindgut to determine what differences exist. The insight gained from this analysis will provide a baseline for comparison to understand how gene expression patterns in these tissues adapt to changes in the microbiome and external factors like diet. The results of this thesis are the first steps towards a better understanding of homeostasis in the equine hindgut.
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.