Preliminary results on the relative incorporation of docosahexaenoic and eicosapentaenoic acids into cows milk from two types of rumen protected fish oil

Abstract

Effects of feeding two different types of rumen protected fish oil for 5 days (approximately 1.1 kg of oil per day, containing docosahexaenoic (DHA, C 22:6 ) and eicosapentaenoic (EPA, C 20:5 ) in the ratios of 4.8:1 or 0.6:1; DHA:EPA) on the fatty acid composition of milk from Friesian cows in mid-lactation grazing pasture was examined. Feeding the DHA enriched supplement increased the proportion of DHA and EPA in milk to 2.19% and 1.25%, respectively. There was a major difference in the apparent transfer of DHA and EPA from the diet into milk (7.8% and 21.1%, respectively). In comparison, feeding the EPA enriched supplement the proportions of DHA and EPA increased to 0.69% and 1.36%, respectively. The apparent transfer of DHA and EPA from the protected lipid supplement was similar, being 6.8% and 8.1%, respectively. Both types of fish oil increased the proportion and yield of C 18:1 trans and C 18 conjugated linoleic acid (CLA) in milk fat . The C 18:1 trans was greater in milk fat from the high EPA supplement (13.7% and 17%, DHA and EPA enriched supplement, respectively) and likewise the proportion of c-9, t-11 CLA was greater (2.9% and 5.1%; DHA and EPA enriched supplement, respectively); this may be due to the lower ruminal protection of the high EPA supplement.