PSX-24 - Pre-slaughter factors affecting mobility, blood parameters, bruising, and muscle pH of finished beef cattle in the United States

Abstract: Animal welfare has been a priority in the U.S. slaughter industry for decades, and therefore, a particular emphasis has been placed on minimizing fear, stress, and discomfort in beef cattle as they are marketed through the pre-slaughter period. Still, stressors are an inherent component of this period, and little is known about the impact of these stressors on the welfare and meat quality of finished cattle in the U.S. The aim of the study was to track individual cattle throughout the pre-slaughter period to identify factors associated with key welfare and meat quality outcomes. Data were collected on 454 cattle in the winter and summer; most animals were black-hided (286, 63.7%) and steers (287, 63.2%). Pre-slaughter factors (e.g., distance traveled; truck waiting time; lairage density; lairage duration) were recorded for each study animal. Cattle welfare and meat quality indicators were measured on an individual animal basis. In lairage, cattle mobility was scored using the North American Meat Institute’s 1–4 scale (i.e., normal to extremely reluctant to move). Exsanguination blood was collected from cattle and analyzed for lactate, cortisol, and creatine kinase. Carcass bruising was categorized as: no bruise, one bruise ≤ the size of a deck of cards, one bruise > than the size of a deck of cards, and multiple bruises. Muscle pH was analyzed 32-36 hours postmortem. Aikake Information Criterion was used to assess multi-predictor models. Mobility and bruising were considered binary variables for analysis. Mixed effects linear and logistic regressions were used to analyze continuous and categorical variables, respectively. Longer truck waiting times increased cortisol (P = 0.04) and lactate (P =0.02) concentrations. Similarly, longer lairage durations increased creatine kinase concentrations (P = 0.05) and the odds of carcass bruising (OR: 1.01, CI: 1.0007, 1.0122). Cattle allotted more lairage space had decreased odds of impaired mobility (OR: 0.83, CI: 0.73, 0.96). Compared to summer, winter was associated with lower blood lactate (3.54 ± 0.22 vs. 7.22 ± 0.17 mmol/L (predicted mean ± SE); P < 0.0001) and reduced odds of impaired mobility (OR: 0.26, CI: 0.13, 0.51) and carcass bruising (OR: 0.48, CI: 0.30, 0.78). Muscle pH was not significantly impacted by any measured factor. These findings identify areas for improvement, such as reducing truck waiting times, shortening lairage duration, and providing cattle with more space in lairage. In addition, there may be opportunities for plants to modify their practices at times of the year when cattle may be the most susceptible to adverse welfare events (i.e., summer months). Likely, exposure to multiple stressors during the pre-slaughter period has a compounding effect on cattle welfare and meat quality, and the factors identified in this study are just a few of many important factors requiring further exploration.