Abstract
ABSTRACT The present study aimed to evaluate the feedlot performance, profitability and carcass traits of Brahman bulls classified according to the residual feed intake (RFI). Twenty-four bulls (19-month old, 370±34kg live weight) were housed in individual pens for 54 days and had the daily feed intake (observed dry matter intake, DMIobs; DMI % live weight, LW) and average daily gain (ADG) measured. Ultrasound carcass evaluations were performed at the initial and final weighings, when measurements were taken of Longissimus dorsi area, ratio, Longissimus and Biceps femoris fat thickness. The animals were ranked and divided into high (>+0.5 standard deviation; SD), medium (between ±0.5 SD from the mean), and low (<-0.5 SD) RFI groups. Low-RFI animals had lower DMIobs (P<0.10) and DMI % LW (P<0.05). No significant differences in initial and final weight or ADG were noticed (P>0.05). Low-RFI animals showed lower weight gain cost and higher daily profit (P<0.05). Carcass traits were similar between groups, regardless of evaluation date (P>0.05). Selection for RFI lead to animals with lower feed intake without affecting weight gain or carcass traits, thereby providing increased profitability for beef cattle farming.
Highlights
70% of the total energy consumption in beef cattle production systems is exclusively intended to meet the maintenance requirements of animals (Nutrient..., 1996)
This is because such measures are strongly correlated with weight gain and live weight, thereby causing increases in both adult weight and maintenance requirements of animals, which raises the costs of maintaining dams in herds (Arthur et al, 2001)
Some authors have shown that the carcasses of high-efficiency animals tend to have low subcutaneous and intramuscular fat (Basarab et al, 2003), other studies have found no differences in such traits between high- and lowRFI animals (Cruz et al, 2010; Gomes et al, 2012; Zorzi et al, 2013)
Summary
70% of the total energy consumption in beef cattle production systems is exclusively intended to meet the maintenance requirements of animals (Nutrient..., 1996). Selection based on classic efficiency measures, including feed conversion (FC) and gross feed efficiency (GFE), may fail to improve whole-system efficiency. This is because such measures are strongly correlated with weight gain and live weight, thereby causing increases in both adult weight and maintenance requirements of animals, which raises the costs of maintaining dams in herds (Arthur et al, 2001). Few studies to date have been conducted with the purpose of assessing feed efficiency and the effects of selection for RFI on key production traits in Brahman cattle. The present study aimed to evaluate potential differences in feedlot performance, profitability, and carcass traits in Brahman bulls, classified into feed efficiency groups according to the RFI
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