Ruminal lipid balance and intestinal digestion by dairy cows fed calcium salts of rapeseed oil fatty acids or rapeseed oil.

The effects of supplemental calcium salts of rapeseed oil fatty acids (FA) and rapeseed oil on ruminal metabolism and apparent digestibility of lipids in the small intestine were studied using three multiparous Holstein x Friesian cows in a 3 x 3 Latin square design. Cows fitted with ruminal, duodenal, and ileal cannulas were fed restricted amounts of a control diet (C) containing 65% corn silage and 35% concentrate mix or diet C with supplemental calcium salts of rapeseed oil FA (S) or diet C supplemented with rapeseed oil (O). Fatty acid contents were 1.9, 8.4, and 7.6% for diets C, S, and O, respectively. The average flow of total FA to the duodenum was lower than the intake for supplemented treatments, suggesting catabolism of FA by ruminal microbes. Fatty acid flows at the duodenum were higher (P < .10) for diets supplemented with fat than for diet C, except for C18: 3(n-3) and straight-chain and branched-chain C15 and C17. Fat treatment affected total and individual FA flow to the ileum, except C14:0 and C18:2(n-6) and excreted amount of individual FA, except C14:0, C16:0, and total C18:1. In our trial, the addition of fat, regardless of origin, affected small intestinal digestibilities of C14:0 and C18:2(n-6) and did not affect changes in the amount of FA in the hindgut.