Effect of feeding mixtures of high moisture corn and dry-rolled grain sorghum on ruminal fermentation and starch digestion

Abstract

This experiment was conducted to study the effects of feeding mixtures of high moisture corn (HMC) and dry-rolled grain sorghum (DRGS) on ruminal fermentation and site and extent of starch digestion. Twelve ruminally, duodenally and ileally fistulated sheep were assigned to the following treatments: T 1 100% HMC; T 2 67% HMC:33% DRGS; T 3 33% HMC:67% DRGS; and T 4 100% DRGS. Starch and DM intake increased (quadratic, p<0.05) with increasing DRGS. Ruminal starch digestibility (%) decreased (linear, p<0.01) as DRGS was added to the diet (T 1 89.6; T 2 75.4; T 3 70.2; and T 4 51.3) whereas digestion in the small intestine (percentage of intake) increased (linear, p<0.01; T 1 9.2; T 2 22.0; T 3 28.7; and T 4 47.1). Numbers (organisms × 10 3) of total protozoa (quadratic p<0.20; T 1 184.0; T 2 558.5; T 3 250.2; and T 4 130.8) and Entodinium (quadratic, p<0.20; T 1 183.7; T 2 555.9; T 3 244.6; and T 4 118.7) tended to be higher for the grain mixtures. The numbers of Holotrichs ( p<0.05) and ruminal pH decreased linearly ( p<0.05) with increasing dietary HMC level. The molar proportion of propionate decreased linearly ( p<.01) as HMC increased in the diet. No associative effects were detected in ruminal starch digestion when both DRGS and HMC were in the diet. However, the elevated number of protozoa observed when HMC and DRGS were combined may have an effect on the site of starch digestion.