RESUMEN
Two studies were conducted to evaluate the effects of abomasal carbohydrate infusion on nutrient digestibility and fecal measures. In Exp. 1, 5 Holstein steers were assigned to a Latin square with 1-wk periods and were abomasally infused on a single day at the end of each period with water alone, a single pulse dose of water with 1 g/kg BW oligofructose or cornstarch, or 4 pulse doses of water with 0.25 g/kg BW oligofructose or cornstarch administered every 6 h. Total tract nutrient digestibility was not affected by treatment except for a tendency for a decrease in starch digestibility in response to the 1 g/kg BW dose of cornstarch ( < 0.10). Compared with the control, both oligofructose and starch infusions caused similar decreases in fecal pH ( < 0.05) and increases in fecal short-chain fatty acids ( ≤ 0.01) measured 12 h after the first infusion, with the single 1 g/kg BW infusions causing a greater magnitude of pH change compared with the four 0.25-g/kg BW infusions ( < 0.01). All treatments increased concentration of fecal lipopolysaccharide compared with the control for at least 1 time point following the infusion ( < 0.05), with a greater increase observed for the 0.25 g/kg BW infusions of oligofructose compared with the other treatments ( < 0.05). Results of Exp. 1 indicate that both oligofructose and cornstarch infusions increased carbohydrate fermentation in the intestines and can be used as a method to evaluate the impact of excessive intestinal fermentation on intestinal health. In Exp. 2, 6 Holstein steers received abomasal pulse doses of 0 (control) or 10 g/d live var. (SB) according to a crossover design with 18-d periods. Abomasal infusions of 4 pulse doses of 0.25 g/kg BW oligofructose administered every 6 h were conducted on d 16 of each period. During the baseline period prior to the oligofructose challenge, there were no effects of SB on fecal measures except for an increase in apparent total tract NDF digestibility ( < 0.05), suggesting that SB increased intestinal fiber fermentation. During the oligofructose challenge, SB increased fecal score ( = 0.03) and tended to reduce fecal short-chain fatty acids ( = 0.10). Results of Exp. 2 suggest that abomasal SB modestly stabilized the intestinal environment during increased carbohydrate fermentation.