Prediction of physical and chemical body compositions of purebred and crossbred Nellore cattle using the composition of a rib section

The goal of this research was to develop empirical equations to predict chemical and physical compositions of the carcass and the body using the composition of the 9th- to 11th-rib section (rib(9-11)) and other measurements. A database (n = 246) from 6 studies was developed and comprised 37 bulls (BU), 115 steers (STR), and 94 heifers (HF), of which 132 were Nellore (NEL), 76 were NEL x Angus crossbreds (NA), and 38 were NEL x Simmental crossbreds (NS). The right half carcass and the rib(9-11) from the left half carcass were analyzed for ether extract (EE), CP, and water. The remaining components were chemically analyzed to determine the composition of the body. A stepwise procedure was used to determine the variable inclusion in the regression models. The variables included were EE in the rib(9-11) (EER; %), CP in the rib(9-11) (CPR; %), water in the rib(9-11) (WR; %), visceral fat (VF; %; KPH and mesenteric fats), organs plus viscera (OV; %), carcass dressing percentage (CD; %), cold carcass weight (kg), and empty BW (EBW; kg). No sex or breed effects were found on EE and CP compositions of the carcass (C-EE and C-CP, respectively; %); the equations were as follows: C-EE = 4.31 + 0.31 x EER + 1.37 x VF [ n = 241; R-2 = 0.83; mean square error (MSE) = 4.53] and C-CP = 17.92 + 0.60 x CPR -0.17 x CD (n = 238; R-2 = 0.50; MSE = 1.58). Breed affected water content in the carcass (C-W, %); the equations were as follows: C-W = 48.74 + 0.28 x WR - 0.017 x EBW for NEL; C-W = 46.69 + 0.32 x WR - 0.017 x EBW for NA; and C-W = 38.06 + 0.48 x WR - 0.017 x EBW for NS (n = 243; R-2 = 0.67; MSE = 5.17). A sex effect was found on body chemical EE composition (BWEE); the equations were as follows: BWEE = 2.75 + 0.33 x EER + 1.80 x VF for BU; BWEE = 1.84 + 0.33 x EER + 1.91 x VF for STR; and BWEE = 4.77 + 0.33 x EER + 1.28 x VF for HF (n = 243; R-2 = 0.89; MSE = 3.88). No sex or breed effects were found on CP composition in the body (BWCP); the equation was as follows: BWCP = 14.38 + 0.24 x CPR (n = 240; R-2 = 0.59; MSE = 1.06). A sex effect was found for body water content (BWW); the equations were as follows: BWW = 38.31 + 0.33 x WR - 1.09 x VF + 0.50 x OV for BU; BWW = 45.67 + 0.25 x WR - 1.89 x VF + 0.50 x OV for STR; and BWW = 31.61 + 0.47 x WR - 1.06 x VF + 0.50 x OV for HF (n = 241; R-2 = 0.81; MSE = 3.84). The physical carcass composition indicated a breed effect on all components and a sex effect for fat in the carcass. We conclude that body and carcass compositions can be estimated with rib(9-11) for purebred and crossbred NEL animals, but specific equations have to be developed for different groups of animals.