Abstract The objective of this study was to assess the relationship of health status to EPD, growth, performance, carcass, and fertility metrics in Angus, Red Angus, and Simmental yearling bulls. For producers that continue to genetically select for lower actual BW, lower BW EPD, and higher CED EPD, it raises the question of whether placing selection pressure on these traits is associated with the health status of bulls during the growing phase. Poor health status has previously been associated with decreased feedlot performance and carcass characteristics. Further analysis is required to understand the relationship between health status, performance, and carcass traits in developing bulls within a bull test selection scenario. Health status was determined by number of times that the bull was treated with an antibiotic during the growing bull phase (M = 0.8358, SD = 1.431). Actual BW, CED, and BW EPD were taken from respective breed association databases. Performance metrics of average daily gain (ADG) and weight per day of age (WDA) were calculated during the growing bull phase. Carcass metrics including rib eye area (REA), intramuscular fat (IMF), and 12th rib backfat (BF) were obtained using ultrasound. Scrotal circumference (SC) was measured by a veterinarian as an indicator trait of fertility. Angus (n = 102), Red Angus (n = 15), and Simmental (n = 96) bulls were included across five contemporary groups of bull test data. Data were analyzed using the PROC CORR procedure of SAS. There was no correlation of health status to BW (P ≥ 0.22), BW EPD (P ≥ 0.09), or CED EPD (P ≥ 0.09) or SC (P ≥ 0.34) in any breed. Carcass metrics were not related (P ≥ 0.09) to health status across both Angus and Simmental bulls. As number of treatments decreased, ADG increased in Angus bulls (r = -0.36; P 0.01) and Simmental bulls (r = -0.33; P 0.01). As number of treatments increased, WDA decreased in Red Angus bulls (r = -0.53; P = 0.04). As number of treatments increased in Red Angus bulls, a corresponding decrease was observed (P £ 0.06) in BF (r = -0.50) and REA (r = -0.80). In conclusion, health status in the growing bull phase was not related to BW, BW EPD, or CED EPD. An increase in the number of treatments was related to a decrease in performance metrics across breeds and a decrease in carcass traits in Red Angus bulls. Fertility as determined by scrotal circumference was not related to health status.
Mathew et al. (Wed,) studied this question.