Performance and welfare-centered strategies in the beef industry: heat stress management, pain mitigation, and diagnostics

Abstract

The objective of this dissertation is to explore both performance and welfare-based strategies within the beef industry to enhance cattle production and operational profitability by providing evidence-based management practices. The first chapter consists of a systematic literature review describing a diverse range of heat stress mitigation strategies employed within the feedyard sector and their effects on cattle performance, behavior, and physiological outcomes. A total of five studies were designed and conducted to describe two different heat stress mitigation strategies (Chapters 2 and 3), gross lesions at mortality (Chapter 4), prognostic abilities of biomarkers (Chapter 5), and effects of pain mitigation at castration (Chapter 6). Two randomized controlled trials, consisting of approximately 8000 steers each, focused on strategies to mitigate heat stress within a commercial feedyard operation in the Pacific Northwest. One of these studies aimed to determine the effects of shade on steer performance, behavior, and carcass outcomes after a terminal sort event. The second study aimed to determine the effects of night-time feeding on steer performance, behavior, and carcass outcomes after a terminal sort event. Outcomes measured in both studies included daily feed delivery, water consumption, open mouth breathing prevalence, and disease events. Overall average daily gain and feed conversion were also calculated. Carcass traits recorded included final live weight, hot carcass weight, quality grade, yield grade, and dark cutter count. Overall, shade inclusion was seen to decrease water consumption, open mouth breathing prevalence, culling events, and dark cutter counts, while increasing the proportion of steers grading prime and choice vs select. No effects were seen between the night-fed group compared to the morning-fed group; however, the environmental heat load during the summer of this study was very mild, as measured and recorded by the Temperature-Humidity Index. The impact of shade in this dissertation, as well as previously published literature, show benefits of proving shade to cattle on feed as a heat stress mitigation strategy. Further research is warranted on the effects of night-time feeding on heat stress mitigation, especially in the face of greater environmental heat burden. One observational study was conducted over two summers in the Great Plains region, where approximately 800 mortalities within commercial feedyards were systematically necropsied. All gross lesions, or abnormalities, were recorded for each necropsy. Feedyard mortalities commonly exhibited multiple concurrent lesions, averaging 2.3 lesions per animal. The most common concurrent lesions seen consisted of pulmonary and gastrointestinal lesions, which agree with the most common diagnoses recorded in feedyard mortalities. Additionally, the probability of having more than one lesion or more than one body system affected increased as days on feed at death increased. Performing systematic necropsies and recording all lesions can help producers and veterinarians establish or modify evidence-based treatment protocols for morbidities, with the goal to improve overall performance. Another observational study was conducted to determine potential associations between cardiac troponin (cTnI) serum concentration in cattle arriving at a commercial feedyard hospital for initial treatment of bovine respiratory disease, with the risk of retreatment, mortality, or culling within 60 days of first treatment. Blood was collected from over 300 steers and heifers, and 60-day outcomes were obtained. cTnI concentration was determined using an ELISA assay, and then further binomialized as LOW (< 0.156 ng/mg) or HIGH (≥ 0.156 ng/mg). The majority of samples had LOW cTnI concentrations; however, cattle with HIGH cTnI concentrations at first bovine respiratory disease treatment had a greater probability of not finishing the 60-day window due to either death or culling, compared to cattle with LOW cTnI concentrations. Though cTnI concentrations may be valuable as an additional prognostic tool in a commercial feedyard, further research is needed to determine the optimal cTnI cutoff value. Lastly, a single randomized controlled trial was performed to compare the use of lidocaine-infused castration bands to standard castration bands with no pain mitigation on 26 beef-dairy calves’ performance and welfare. Calves were monitored for 7 weeks post-banding, and outcomes measured included body weight, average daily gain, feed conversion, clinical illness scores, banding site scores, physiological markers, as well as multiple different measures of animal behavior. Differences in behavior between these groups were observed close to time of scrotal sloughing, indicating the calves banded with the lidocaine-infused castration bands had less pain; however, no differences were seen in overall performance or physiological markers, indicating both groups experienced acute and chronic pain post castration. Further research could help researchers better understand the implications of pain mitigation around time of castration in calves on performance and welfare. In conclusion, the studies presented in this dissertation evaluated strategies aimed at improving cattle performance and welfare. Collectively, these studies advance our understanding of management practices, necropsy evaluation, and welfare interventions that can improve cattle heath, productivity, and decision making in commercial beef production.