Development and evaluation of models to estimate body chemical composition of young Nellore bulls

Abstract

-The objective of this study was to develop accurate regression equations to predict body composition of Nellore cattle using chemical composition of the 9th, 10th, and 11th ribs and to evaluate the models proposed by analyzing mean and linear bias. Sixty-seven Nellore bulls were slaughtered and slaughter body weight (SBW), hot carcass weight (HCW), and 9th-, 10th-, and 11th-rib-cut weight (RCW) were measured. Empty body composition was obtained after grinding, homogenizing, sampling, chemical analysis, and pooling (blood, skin, head + feet, viscera, and carcass). Chemical components were determined in rib cut, carcass, and empty body: protein (RCP, HCP, and EBP), fat (RCF, HCF, and EBF), ash (RCA, HCA, and EBA), and water (RCWt, HCWt, and EBWt). Stepwise options were used to determine variables to be included and excluded from regressions. Predictive ability of equations was verified using standard error of prediction, coefficient of determination, and Cp statistic. Regression estimates were tested to evaluate the models in a database different from that used for equation development.

Empty body chemical composition of Nellore steers estimated by indirect methods

“…Water, fat, protein, and ash are body components of greatest interest for beef cattle nutrition. These components are distributed in a varied way in body tissues according to different factors and are important in dynamic models to estimate body composition (SILVA et al, 2017).…”

“…The most traditional indirect method is the use of 9-10-11 th ribs, recommended by Hankins and Howes (1946). Many studies have investigated this method and some errors in the estimates were found, although the method has been validated in several circumstances (SILVA et al, 2017;NEVES et al, 2018).…”