Estimation of Metabolizable Amino Acids and Energy Requirements and Development of Mathematical Models to Predict Average Daily Gain for Beef Cattle

This study aimed to estimate metabolizable energy (ME), protein (MP) and amino acids (MAA) requirements for maintenance and growth, and to develop a mathematical model to predict ADG for beef cattle using a meta-regression approach. A data set including 91 sources of literature with 385 treatments was assembled after data collection and screening. To estimate nutrient requirements for maintenance and growth, metabolizable nutrient intakes were regressed on metabolic body weight (MBW) and ADG using a mixed model with a random study effect. A multiple linear regression model was derived to predict ADG using MBW and nutrient intakes as independent variables. The random forest analysis was used to identify the importance of independent variables associated with ADG and compare it with the multiple linear regression model. The accuracy of the model was evaluated by Monte−Carlo cross-evaluation. The ME and MP requirements for maintenance were 0.56 MJ/BW^0.75 and 4.31 g/BW^0.75. The maintenance requirements of metabolizable arginine (Arg), histidine (His), isoleucine (Ile), leucine (Leu), lysine (Lys), methionine (Met), threonine (Thr), tryptophan (Trp), phenylalanine (Phe), valine (Val) and total AA were 0.044, 0.073, 0.013, 0.13, 0.10, 0.024, 0.075, 0.026, 0.088, 0.11 and 0.76 g/BW^0.75. The estimated ME and MP requirements for growth were 45.8 MJ/kg ADG and 398.7 g/kg ADG. The growth requirements of metabolizable Arg, His, Ile, Leu, Lys, Met, Thr, Trp, Phe, Val and total AA were 4.5, 6.4, 7.3, 24.0, 2.9, 2.4, 6.1, 1.7, 9.5, 9.3 and 74.5 g/kg ADG. The multiple linear regression analysis showed that ADG was positively correlated with intakes of ME, ether extract, starch and Trp (p < 0.05). The results of the Monte−Carlo cross-evaluation showed that the multiple regression model was more accurate in predicting ADG than the random forest model. ME and MP requirements for maintenance are consistent with previous studies, but requirements for growth tend to be overestimated. Future studies are needed to evaluate MAA requirements. An accurate model was developed to predict ADG, offering a theoretical basis and guidance to improve growth performance and feed conversion efficiency for beef cattle.