Effects of mixing Stylosanthes conserved as hay or silage with corn silage in diets for feedlot beef cattle

The objective of this study was to evaluate the total and partial digestibility, ruminal pH and ammonia nitrogen (NH3-N) concentration, nitrogen balance (Experiment 1) and performance (Experiment 2) of beef cattle fed diets containing corn silage (CS) and Stylosanthes (silage or hay) as forage source. Treatments were: 1) CS; 2) Stylosanthes silage (StS); 3) Stylosanthes hay (StH); 4) CS + StS (StS-mixed diet); and 5) CS + StH (StH-mixed diet). Experimental diets (125 g CP/kg DM) consisted of 50% forage and 50% concentrate (DM basis). Five cannulated bulls (251 ± 42.6 kg of body weight) were distributed to a 5 × 5 Latin square (Experiment 1). The trial lasted 80 d. The experiment 2 was performed with 40 bulls (360 ± 2.7 kg of body weight) in a completely randomized design and eight replicates during a 99-days period. In experiment 1, CS diet showed greater (P ≤ 0.02) total digestibility of DM, OM, CP and NDF than other diets. Mixed diets had greater (P = 0.02) total NDF digestibility compared to StS and StH. Corn silage showed greater total digestibility of DM, OM, NDF and CP (P ≤ 0.03) compared to mixed diets. Ruminal NDF digestibility was greater (P = 0.03) for CS than other diets. Ruminal pH was greater (P