# Evaluation of calcium β-hydroxy-β-methylbutyrate on performance of Bos indicus-influenced cattle in a subtropical environment

## TL;DR

This study shows that adding calcium β-hydroxy-β-methylbutyrate (CaHMB) to the diet of Bos indicus bulls improves their growth and carcass yield in a hot climate.

## Contribution

The study demonstrates the effectiveness of CaHMB in improving performance of Bos indicus cattle in subtropical conditions.

## Key findings

- Bos indicus bulls supplemented with CaHMB showed increased final body weight and average daily gain.
- Carcass weight and dressing percentage improved with CaHMB supplementation.
- No significant changes in feed intake or gain:feed ratio were observed.

## Abstract

Improving beef cattle feedlot performance is important to facilitate the increasing world demand for beef. The leucine metabolite, β-hydroxy-β-methylbutyrate (HMB), has shown potential to improve feedlot performance in Bos taurusbred cattle when fed as the calcium salt (CaHMB). Data from this trial indicated that the use of CaHMB is justified for cattle in tropical regions.

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.

Graphical Abstract