Effect of flint corn processing methods on intake, digestion sites, rumen pH, and ruminal kinetics in finishing Nellore bulls

Abstract

This study aims to (1) verify the influence of flint corn processing methods on intake; rumen digestion kinetics; microbial efficiency; rumen pH; and ruminal, intestinal, and total tract digestibilities in Nellore bulls; and (2) determine whether snaplage (SNAP) plus a mineral–protein supplement could be used successfully to supply energy, fiber, and protein in a finishing diet without causing ruminal acidosis. Five rumen-cannulated Nellore bulls (265 ± 18.2 kg, 8 ± 1.0 mo old) were distributed in a 5 × 5 Latin square design. Five different diets were evaluated. Three experimental diets [dry matter (DM) basis] comprised 600 g/kg dry ground corn grain (DCG), high–moisture corn (HMC), or reconstituted corn grain silage (RCG) plus 300 g/kg whole-plant corn silage and 100 g/kg mineral–protein supplement. SNAP was included in two experimental diets, namely 900 g/kg SNAP (SNAP-90) or 800 g/kg SNAP +100 g/kg stalklage (SNAP-80) plus 100 g/kg mineral–protein supplement. The experiment lasted 115 d, with five periods of 23 d. These periods were divided into two subperiods of 14 d for dietary adaptation and 9 d for ruminal emptying, omasal, urinary, and fecal sample collection. Statistical analyses were performed using the MIXED procedure in SAS 9.4. DCG-based diet tended (P = 0.07) to increase DM and organic matter (OM) intake. Diets based on HMC, RCG, SNAP-80, and SNAP-90 increased (P < 0.05) intestinal and total digestion of DM, OM, and starch compared with the diet based on DCG. There was greater (P < 0.05) microbial crude protein synthesized per kg of crude protein intake for bulls fed HMC-based diet compared with bulls fed DCG-, SNAP-80-, or SNAP-90-based diets. Intake and passage rates of starch were lower (P < 0.05) and digestion rate of starch tended to be lower (P = 0.06) for DCG-based diet compared with the other diets. The rumen pH was affected (P < 0.05) by diets. However, rumen pH was above 6.2 for all evaluated diets. Also, there was no effect of flint corn processing methods on ruminal, intestinal, and total tract digestibility of fiber. In conclusion, diets based on HMC, RCG, SNAP-80, and SNAP-90 can be used to improve starch availability without negatively affecting ruminal parameters. HMC and RCG are viable processing methods for flint corn and can replace DCG to improve nutrient digestibilities. In addition, SNAP could be used as an exclusive fiber and energy source for feedlot-finished Nellore bulls.