Estimated beef cattle performance under intensive grazing systems in Uruguay

The objective of this study was to analyze the effect of the quantity and quality of the feed offered on the performance of male beef cattle, >6 months old, on intensive grazing systems in Uruguay. Two hundred and fifty-four results from different experimental trials (nexp=68) performed between 1991 and 2020 by different research institutions in Uruguay were compiled and analyzed. The experiments included feeding studies with cultivated pastures as a single nutritional source (nexp=61), as well as supplementation studies on the same type of pastures (nexp=49). Simple, quadratic, multiple linear regressions and recursive partitions were performed to synthesize the information. Quadratic relationships between forage allowance (FA) and average daily gain (ADG) were observed for the different animal categories and seasons of the year. Including other parameters such as initial body weight and supplementation with energy concentrates or silages allowed to predict the ADG of animals under a wide range of feeding alternatives. Briefly, low FA levels (≤1.75 %BW) limit animal performance to maintenance gain conditions (0.2 kg/day). To achieve adequate levels of ADG (0.6-0.7 kg/day), with a low to moderate FA (between 1.75 to 3.5 %BW), the nutritional value of pasture needs to reach at least level 3 of quality (>58 %ODM, >13 %CP, 21 %Leg and 3.5 %BW (ADG in the range of 0.7 to 1.0 kg/day). The increased response in additional ADG (0.4-0.5 kg/day) by the effect of supplementation with energy concentrate was achieved with low FA levels (≤2.25 %BW). The prediction of additional ADG using a multiple linear regression parameter allows evaluating whether supplementation is appropriate.