Abstract
The objective of the present study was to analyze the phenotypic inter-relationships between growth, feed intake and carcass traits in polled Nellore cattle, as well as to determine which bulls produced the most efficient progeny. The experiment was conducted in the feedlot of the Guaporé Pecuária (Livestock) Company, OB Brand. The following traits were analyzed: initial live weight (ILW); final live weight (FLW); average daily gain (ADG); dry matter intake (DMI); gain:feed (G:F); residual feed intake (RFI); rib-eye area (REA); rump fat thickness (RF); backfat thickness at the 12th-13th rib (BF); weighted fat score (WF); and intramuscular fat percentage (IMF). Both univariate and multivariate analyses were performed to analyze the inter-relationships between the studied traits. No significant phenotypic associations were observed between growth, carcass traits and residual feed intake, while the correlation between RFI and G:F was negative. Therefore, RFI may be used to select more nutritionally efficient animals without compromising growth or adult size. The selection of bulls with progeny showing low residual feed intake is recommended, as selection for low RFI tends to improve feed efficiency without compromising growth and development.
Highlights
The Brazilian beef industry has grown rapidly in recent years and the growth in beef production is estimated to reach 4.4%/year by 2015. This prediction is supported by data showing Brazil as first in world exports of beef, second largest producer of veal and third largest consumer in the world (BRAZIL, 2011)
Several researchers have studied growth characteristics such as weights at different ages, growth curves and features related to the standard growth rate of Nellore (GUSMÃO et al, 2009; LOPES et al, 2011; LOPES et al, 2012; SANTOS et al, 2012; SOUZA et al, 2008)
Residual feed intake is defined as the difference between the estimated food consumption and the observed food consumption: it is a measure of feed efficiency which presents estimates of genetic and phenotypic correlations close to zero with muscle score at weaning, weaning weight adjusted to 210 days and feed intake and low genetic correlation with feed conversion ratio(BOUQUET et al, 2010)
Summary
The Brazilian beef industry has grown rapidly in recent years and the growth in beef production is estimated to reach 4.4%/year by 2015. Residual feed intake is defined as the difference between the estimated food consumption and the observed food consumption: it is a measure of feed efficiency which presents estimates of genetic and phenotypic correlations close to zero with muscle score at weaning, weaning weight adjusted to 210 days and feed intake and low genetic correlation with feed conversion ratio(BOUQUET et al, 2010). This indicates that different sets of genes influence growth characteristics and residual feed intake. The adoption of the latter as a tool to select more efficient animals should not compromise the adult size of animals selected for this trait
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