The objective of the experiment was to evaluate the use of soybean straw as partial substitute for sorghum silage in the roughage fraction of the diet of confined calves, being tested the following treatments: T0 with 100% of sorghum silage; T33 with 66.67% of sorghum silage plus 33.33% of soybean straw; T66 with 33.33% of sorghum silage plus 66.67% of soybean straw. The diets were fed during 77 days for Charolais-Nellore crossbred calves with an initial average weight and age of 165.6 kg and 11 months, respectively. The diets contained 14% of crude protein in the dry matter (DM), with 20% supplied in the form of urea. The roughage:concentrate ratio was of 70:30 (DM basis). The data were submitted to regression analysis, being obtained the following regression equations: for average daily gain in kg (ADG) = 1.166273 - .00186 IW (initial weigh) - .00351 SL (substitution level); daily dry matter intake in kg/100 kg live weigh (DMILW) = 2.284983 + .002679 IW - .002303 SL; daily digestible energy intake Mcal/100 kg live weigh/day (DEILW) = 5.709589 + .010964 IW - .018736 SL; food convertion (FC) = - 4.42 6857 + .064579 IW + .023165 SL. It was verified that for each increase of 1% in the substitution of the sorghum silage by soybean straw, occured a decline of 3.51g in ADG, 2.3g in DMILW, while food convertion worsen .023 units. The increase of the proportion of soybean straw in the diet in substitution to sorghum silage causes a linear decline in animal performance. However, even in the highest substitution level, weight gain is still satisfactory.
feed intake; food convertion; weight gain; straw; crop residue
