Effects of including physically effective fiber from sugarcane in whole corn grain diets on the ingestive, digestive, and ruminal parameters of growing beef bulls

Abstract

The objective of this study was to evaluate the inclusion of physically effective fiber (peNDF) from sugarcane in feedlot diets containing whole corn grain on ingestive, digestive, and ruminal parameters. Five rumen-cannulated Nellore bulls (BW = 393 ± 9 kg) distributed in an incomplete 5 × 5 Latin square received diets containing 5% (D5), 15% (D15), 25% (D25), or 35% (D35) sugarcane. All diets included a mineral-protein supplement. Omasal digesta collection and fecal spot collection were carried out to estimate ruminal and total digestibility. The ruminal contents were emptied to calculate ingestion (ki), passage (kp), and digestion (kd) rates. The linear, quadratic, and cubic effects of including sugarcane (i.e., different peNDF contents) were evaluated using orthogonal contrasts. The intake of total digestible nutrients (TDN, P = 0.06), dry matter (DM, P = 0.03), and organic matter (OM, P = 0.03) showed a quadratic pattern, with the highest estimated values occurring between 6.14 and 10.2% of peNDF. Ruminal digestibility [%, (P = 0.01) and kg/d, (P = < 0.01)] and total digestibility (kg/d, P = 0.03) of OM, ki (P = < 0.01), kp (P = 0.01) and kd (P = < 0.01) rates of OM, ki (P = 0.07), kp (P = 0.01), and kd (P = 0.05) rates of neutral detergent fiber (NDF) and microbial crude protein synthesis (MPS) (P = < 0.01) were also maximized, with inclusion levels between 6.14 and 10.2% of peNDF, although the efficiency of MPS tended to increase linearly (P = 0.08). The total concentration of volatile fatty acids (VFA) decreased linearly (P = 0.03), while the rumen ammonia pool [concentration (mmol/L) x volume of rumen liquid (L)] increased linearly (P = < 0.01). Ruminal pH responded linearly with the addition of sugarcane to the diet. We conclude that feedlot animals might benefit from diets containing between 6.14 and 10.2% of peNDF when whole corn grain diets are used.