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 O than for C and S. Under the conditions of this trial, supplemental calcium salts rich in polyunsaturated fatty acids did not decrease ruminal digestion.