Fatty acid and triglyceride composition of milk fat from lactating Holstein cows in response to supplemental canola oil

The objective was to determine the influence of dietary lipid on total and sn-2 fatty acid composition and triglyceride structure of milk fat in lacta ting Holstein cows. Five primiparous Holstein cows surgically fitted with r uminal and duodenal cannulas were used in a 4 X 5 incomplete Latin square. All cows received a basal diet. Treatments consisted of a basal diet with n o supplemental canola oil (control), basal diet with canola oil added to th e concentrate portion of the diet to provide 1.6% fat, basal diet with 330 g of canola oil infused directly into the rumen, and basal diet with 330 g of canola oil infused directly into the abomasum. Canola oil treatments dec reased palmitic acid and increased oleic acid content of milk fat compared with the control. Stearate was higher when canola oil was rumen available c ompared with control and abomasal infusion. Abomasal infusion increased lin oleic and linoleic acids in milk fat compared with the other treatments. Th e sn-2 fatty acid composition reflected total fatty acid composition. All c anola oil treatments reduced palmitic acid and increased oleic acid content at the sn-2 position. Changes in sn-2 composition reflect specificity of t he acyl transferases and substrate concentration. Triglyceride composition reported as carbon number was altered by canola oil. Triglycerides in carbo n number C50, C52, and C54 were increased while C32, C34, and C36 were decr eased.