Modelos matemáticos de predição de consumo, desempenho e características de carcaça de bovinos Nelore terminados em confinamento

Abstract

The objective was to develop and evaluate models to predict dry matter intake, productive performance and carcass characteristics through performance and intake measures of Nellore cattle finished in feedlot. Two articles were developed, in chapter 1, were used individual data from five feedlots developed between 2016 and 2020 at the Fazenda Escola da Faculdade de Medicina Veterinária e Zootecnia of the Universidade Federal de Mato Grosso do Sul (UFMS), totaling 144 non-castrated male Nelore cattle and slaughtered at 24 months old, with an average initial body weight of 345 Kg±42 and an average final weight of 497 Kg±57, in which productive performance was evaluated (average daily gain, total feedlot gain, slaughter weight, carcass yield, hot carcass weight, loin eye area and subcutaneous fat thickness), in order to predict dry matter intake, final live weight, hot carcass weight, total weight gain and average daily gain. In chapter 2, the same data from the first one were used, plus the last confinement carried out at UFMS, in 2021, with 24 non-castrated male Nellore cattle, with the objective of predicting carcass yield, subcutaneous fat thickness, ribeye area and shear force. The mathematical models were evaluated by the coefficient of determination, coefficient of correlation and concordance and square root of the mean square of the error. Thus, the best prediction equations were: for dry matter intake (0,2407 + 0,6200.NDFI + 1,0775.TDNI + 0,0007.TWG), final body weight (11,9822 + 1,3158.NDFI + 0,9533.IBW + 0,9927.ADG, and -142,1223 + 0,9709.TDNI + 0,9468.IBW + 112,8006.ADG + 1,3538.DC), hot carcass weight (0,1971.IBW + 0,4476.FBW – 0,2190.DC), total weight gain (– 164,8646 + 0,0181.FBW + 1,4038.DC + 110,7189.ADG), average daily gain (0,0135.DMI – 0,0051.IBW + 0,0059.FBW), slaughter carcass (3,2829.CPI – 0,8286.TNDI + 0,0246.FBW – 0,3836.TWG + 0,4195.DC + 39,6007.ADG, and 1,5497.CPI + 0,9562.DC – 0,0043.DC² – 0,3252.ADG²), subcutaneous fat thickness (5,1928.DMI – 0,1862.DMI² – 9,2198.NDFI + 0,9344.NDFI² – 0,6565.TDNI – 0,0338.DC), ribeye area (– 0,3149.DMI² + 69,1469.CPI + 0,4006.DC – 0,0032.DC²) and shear force (2,3139.CPI – 0,0421.TDNI² + 0,0711.DC – 1,1557.ADG), where DMI = Dry matter intake (kg/day), CPI = Crude protein intake (kg/day) NDFI = Neutral detergent fiber intake (kg/day); TDNI = Total digestible nutrients intake (kg/day); FBW = Final body weight (kg); TWG = Total weight gain (kg), ADG = Average daily gain (kg/day); DC = Days in confinement. Intake, performance and confinement time measures can be used as predictors of dry matter intake, performance trait and carcass. The prediction equations for dry matter intake, final live weight, warm carcass weight, total weight gain, average daily gain and rib eye area showed satisfactory precision and accuracy for non-castrated Nellore cattle finished in confinement systems under conditions tropical.