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

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 x 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. (C) 1999 Elsevier Science B.V. All rights reserved.