Evaluation of calcium β-hydroxy-β-methylbutyrate on performance of <i>Bos indicus</i> -influenced cattle in a subtropical environment

β-Hydroxy-β-methylbutyrate (HMB), a metabolite of leucine, increases both protein synthesis and lipolysis, immune function, and overall health in both humans and animals. Previous cattle studies have shown that HMB, fed as calcium HMB (CaHMB), can minimize stress responses and improve meat quality. The objective of the present study was to investigate the effect of feeding CaHMB in a subtropical feedlot on performance of Nellore (Bos indicus) bulls. A total of 3,520 bulls (64 pens; 55 animals per pen) were studied with four levels of CaHMB (0 [control, CON], 3, 5, or 7 g per head per day) and half the pens had shade access (SH), and half did not in a split-plot experimental design. Diets containing CaHMB were fed during three phases of the study, adaptation, growth, and finishing. There were no CaHMB × SH interactions observed for any variable measured. However, adjusted final body weight (FBW) tended to increase in CaHMB-treated bulls up to 5.8 kg in bulls fed 3 g per day (linear P < 0.07). Additionally, adjusted average daily gain (ADG) and carcass ADG were also increased with 3 g per day CaHMB by 3.2% and 2.6%, respectively, when compared with CON (linear P < 0.04). Bulls fed CaHMB tended to have increased hot carcass weight (HCW) by up to 3.4 kg in bulls fed 3 g CaHMB per day and a 0.36% increase in dressing percentage (DP) (linear P < 0.07 and 0.09, respectively). No differences were observed in dry matter intake (DMI) during any of the feeding periods. No significant differences were observed in gain:feed. Of major importance to the subtropical environment, 34% of the days were considered hot to very hot with the comfort level (InCI) >0.45 on a 0 to 1.0 scale. In conclusion, supplementing Bos indicus bulls with CaHMB resulted in improved growth performance and carcass yield.