ORGANIC-MATTER AND NITROGEN DIGESTION BY DAIRY-COWS FED CALCIUM SALTS OF RAPESEED OIL FATTY-ACIDS OR RAPESEED OIL

The aim of this experiment was to study the effects on digestion of a supply of Ca salts of vegetable oil as a fat source for ruminants. Total tract digestibility and ruminal digestion were studied using three ruminally and duodenally fistulated dairy cows in a Latin square design. Diets compared were a control diet (C) based on corn silage and concentrate, and the C diet supplemented with calcium salts of rapeseed oil (S) or supplemented with rapeseed oil (O). Organic matter digestibility was lower (P < .05) for diet O than for diet C; diet S was intermediate and not different (P > .05) from diet C. Treatment did not affect (P > .05) the proportion of OM digested in the rumen, total N and microbial N flow at the duodenum, or efficiency of N microbial synthesis. In situ degradation of DM and NDF was higher for diet S than for diet C. The molar concentration of ruminal acetate was lower (P < .05) for 0 than for C and S. Under the conditions of this trial, supplemental calcium salts rich in polyunsaturated fatty acids did not decrease ruminal digestion.