Total nutrient digestibility and small intestine starch digestion in Nellore and Nellore × Angus steers fed whole shelled corn-based diet with or without roughage

This study aimed to evaluate total nutrient digestibility, pancreatic α‐amylase, and the expression of maltase-glucoamylase (MGAM) and solute carrier family 5 member 1 (SLC5A1) in the small intestine in Nellore and Nellore × Angus steers fed whole shelled corn-based diet with or without inclusion of sugarcane bagasse as a roughage source. Sixteen Nellore and 16 Nellore × Angus steers with 353 ± 25.3 kg were allotted in a completely randomized design using a 2 × 2 factorial arrangement (2 breeds and 2 diets). The two experimental diets [dry matter (DM) basis] comprised: 800 g/kg of whole shelled corn and 200 g/kg of protein-mineral pellet (WSC) or 740 g/kg of whole shelled corn, 200 g/kg of protein-mineral pellet, and 60 g/kg of sugarcane bagasse (WSCB). The intake of DM and other dietary components were greater in steers fed WSCB than in steers fed WSC (P < 0.01). However, WSCB decreased the total tract digestibility of DM, organic matter, crude protein, neutral detergent fiber, and total digestible nutrients (P ≤ 0.01) and tended to decrease ether extract digestibility (P = 0.08). There were no effects of breed on DM intake, nutrient intake, or nutrient digestibility (P > 0.10). Feeding WSCB to steers increased fecal output as well as starch excretion in feces (P < 0.01), whereas it tended to decrease starch in feces when expressed as a percentage (P = 0.09). Steers fed WSCB had greater pancreatic α-amylase activity (P = 0.03) and tended to have greater MGAM (P = 0.09) expression. On the other hand, animals fed WSC had greater SLC5A1 (P = 0.03) expressions. In conclusion, WSC diet increased total nutrient digestibility. However, there was no effect of diet on total starch digestibility, but the inclusion of sugarcane bagasse may increase small intestine starch digestibility since it has greater pancreatic α-amylase activity and MGAM expression.