RYEGRASS VERSUS CORN STARCH OR BEET PULP FIBER DIET EFFECTS ON DIGESTION AND INTESTINAL AMINO-ACIDS IN DAIRY-COWS

Changes in digestion and AA supply in dairy cows were studied when fre sh grass was partly replaced by concentrate mixtures based either on c om starch or sugar beet pulp fiber. Treatments were tested in a Latin square utilizing three lactating cows with ruminal and intestinal cann ulas. Partial replacement of grass decreased CP digestibility. When hi gh starch concentrate was fed, NDF digestibility was lower than that o f the high fiber diet, mainly because of decreased ruminal digestion o f NDF. For the high starch concentrate, 39% of the ingested starch esc aped ruminal fermentation. Although less OM was fermented in the fores tomachs on high starch concentrate, the duodenal AA N flow was higher than for the high fiber concentrate. The proportion of microbial prote in was unaffected; thus, efficiency of microbial synthesis was estimat ed to be higher when hi h starch concentrate was fed.