Adaptation level can affect performance traits, body and carcass measurements in taurine cattle

Abstract

Heat stress is an important factor in relation to the performance and yield of European cattle breeds in tropical environments. This study aimed to identify if the adaptation level of Angus and Simmental bulls affects their body, carcass, and performance traits. During a performance testing in summer, 100 bulls (N = 40 Angus and N = 60 Simmental) were evaluated for adaptation, body, carcass, and performance traits. At the end of the test, the animals were classified from the highest to the lowest respiratory rate (RR). From that, 20 Angus and 20 Simmental bulls were selected as extreme adaptation levels, in which the 10 with the highest RR were least adapted and the 10 with the lowest RR were the most adapted. These groups of animals were compared for fifteen traits, including the adaptation weight (AW) obtained at the start of the adaptation period, initial weight (IW), final weight (FW), and average daily gain (ADG) as performance traits, body length (BL); body depth (BD), hip length (LENG), and hip width (WID); hip height (HH); and withers height (WH) and heart girth (HG) as body traits and subcutaneous fat thickness (SFT), rib-eye area (REA), and intramuscular fat (IMF) percentage and rump fat thickness (RFT) as carcass traits. Statistical analyses were performed on the RStudio software using the ExpDes package. Statistical difference was considered when P < .05, and means were compared using Tukey’s multiple comparison test. There was a difference in final weight within the least adapted animals (P < .05) – greater for Simmental. The ADG of the most adapted animals was 0.21 kg greater in mean (P < .05) for Angus. At the beginning of the test, BL differed only between breeds, and at the end, it differed between breeds and the adaptation levels (P < .05). The least adapted Angus was 11.5 cm shorter in mean compared to least adapted Simmental and most adapted Angus. Overall, Simmental was longer for other body traits. For carcass traits, only the REA differed (P < .05) between the least adapted animals, being greater for Simmental. The adaptation level thus affected performance, especially for Angus. Therefore, we recommend the evaluation of respiratory rate in performance testing of the Angus and Simmental breeds.