Stylosanthes silage as an alternative to reduce the protein concentrate in diets for finishing beef cattle

The objective of this study was to evaluate the effects of silage and concentrate on nutrients digestibility, ruminal fermentation, efficiency of nitrogen use and animal performance of feedlot beef cattle. Two experiments were conducted simultaneously evaluating the same diets. The forage: concentrate ratio was 50:50 and diets consisted of Stylosanthes (StS) or corn (CS) silages in combination with two concentrates: without (C1) or with soybean meal (C2). In experiment 1, four rumen and abomasum fistulated bulls with an average initial body weight (BW) of 200 +/- 15.7 kg were distributed to a Latin square design with a 2 x 2 (S x C) factorial arrangement (experiment 1). Experiment 2 was conducted using 48 Nellore bulls with an average initial BW of 358 +/- 30 kg, distributed to a complete randomized design with a 2 x 2 factorial arrangement and 12 replicates. In experiment 1, there was an S x C interaction tendency (P <= 0.09) for DM, OM, CP and NDF intakes. Greater intake of DM, OM, CP and NDF was observed for CS with C2. The intake of iNDF was greater (P = 0.01) for StS-based diets. There was a decrease tendency (P = 0.06) on the total CP digestibility in StS-based diets. Nitrogen balance was greater for CS-based diet (P = 0.04). There was an S x C interaction tendency (P = 0.10) for microbial synthesis efficiency (MSE). In experiment 2, C2-based diets showed greater (P < 0.01) intakes of DM, OM and CP. The average daily gain (ADG) and carcass average daily gain (CADG) were greater (P < 0.01) for diets containing the C2. Thus, it is concluded that StS can replace CS in diets of feedlot beef cattle. However, the concentrate source affects animal performance. Stylosanthes silage represents a sustainable alternative for animal production.