Abstract
The objective of this study was to evaluate the correlated responses to selection for growth in feed efficiency and carcass traits of Nellore animals. A total of 121 animals of the Nellore control (NeC) and selection herds were subjected to performance testing and classified regarding residual feed intake (RFI). Sixty-seven of these animals were selected and finished until reaching 4 mm of subcutaneous fat thickness between the 12th and 13th ribs. The animals were slaughtered at a mean age of 541 days and mean live weight of 423 kg for NeS and of 363 kg for NeC, and carcass traits were measured. Animals in NeS presented higher initial and slaughter weights, dry matter intake, hot and cold carcass weight, weight of retail cuts, and carcass yield than NeC animals for the same slaughter age and feedlot time. No significant differences in RFI were observed between herds, showing that the weight gain from selection for growth did not cause changes in the energy efficiency of the animals.
Highlights
The beef cattle production system is constantly changing to meet the requirements of sustainable agriculture and consumer demands for meat quality
The objective of the present study was to evaluate the correlated responses to selection for postweaning weight in feed efficiency and carcass traits of Nellore cattle
In the case of feedlot management in which about 80% of the costs are destined for feeding, the identification of animals that consume less feed without compromising production would result in major cost reductions for the system
Summary
The beef cattle production system is constantly changing to meet the requirements of sustainable agriculture and consumer demands for meat quality. In this respect, various segments of the beef cattle industry are concentrating their efforts to improve product quality, to increase productivity, and to multiply profits. Several studies have investigated the genetic progress of growth traits in selected herds (Packer et al, 1986; Razook et al, 1988, 1993, 1998; Cyrillo et al, 2000). Razook et al (2001) showed that selection for postweaning weight resulted in higher slaughter and carcass weights without altering the yield or quality of the meat produced. Bonilha et al (2008), using the same genetic groups of Nellore but with a larger data set, observed that selection for weight increased the body size of the animals without altering meat yield, body fat percentage or meat tenderness
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