Levels of substitution of corn by soybean hulls in high-concentrate diets for finishing beef heifers

Abstract

We examined the production performance of Nellore heifers fed high-concentrate (90%) diets in which ground corn (GC) was substituted by ground soybean hulls (SH) at increasing levels (0, 33, 66, and 100%), in the concentrate portion. A total of 144 heifers (263.40 ± 13.90 kg average initial weight; 27 months old) received the test diets in a feedlot for 112 days. The experiment was set up as a completely randomised design with four treatments. Data were subjected to ANOVA and orthogonal contrasts, adopting ? = 5%. The sum of squares of treatments in the contrast analysis was decomposed into two orthogonal contrasts (L - linear and Q - quadratic effect) for the level of SH substituting GC. Dry matter intake was not changed by the GC substitution levels, averaging 2.51% of body weight. There was a linear increase in neutral detergent fibre intake (1.08, 2.03, 2.92, 3.78, 4.85 kg/day) and feed conversion (6.20, 7.08, 7.77, and 8.67 kg/kg); and a linear decrease in total digestible nutrient intake (5.78, 5.16, 5.03, 5.12, and 3.66 kg/day), average daily gain (1.24, 1.11, 1.02, and 0.89 kg/day), and slaughter weight (383.52, 374.71, 363.25, and 366.27 kg) as the substitution level was increased (0, 33, 66, and 100%, respectively). Subcutaneous fat thickness and loin-eye area were not influenced (P > 0.05), averaging 5.30 mm and 53.09 cm2, respectively. Substituting ground corn by ground soybean hulls in high-concentrate diets determined a reduction in production performance of feedlot-finished Nellore heifers.