Evaluation of the physical and chemical composition of rib cuts as predictors of body composition of nellore steers
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The objective of this study was to establish equations to estimate the empty body chemical composition of Nellore steers using the following indirect techniques: 1) physical composition of the 9-10-11th rib cut; 2) physical composition of the 10th rib cut; and 3) chemical composition of the 10th rib cut. Thirty-one Nellore steers with weights ranging from 245 to 489 kg and ages from 20 to 29.7 months at slaughter were utilized. The empty body chemical composition was established through samples collected after grinding all animal tissues. The equations using the percentage of dissectable fat in the 9-10-11th rib cut showed a high precision for estimating the percentage of water (r2 = 0.91; Syx = 1.168) and ether extract (r2 = 0.94; Syx = 1.298) of the empty body; the same was observed when the percentage of dissectable fat in the 10th rib cut was used (r2 = 0.82 and 0.85; Syx = 1.658 and 1.942, respectively, for water and ether extract). The equations using the percentage of ether extract in the 10th rib cut showed a high precision for estimating the percentage of water (r2 = 0.89; Syx = 1.311) and the ether extract (r2 = 0.89; Syx = 1.730) of the empty body, but there was no advantage over the physical composition of the 9-10-11th and 10th rib cut. Multiple regressions using carcass weight and the percentage of bones and kilograms of lean, fat, and bones dissectable in the 10th rib cut improved the coefficients of determination for water and ether extract to 0.87 and 0.91. The equations to estimate the percentages of protein and ash showed a low precision, indicating that those techniques are not recommended to estimate these components in the empty body of Nellore steers.