Marine oils are used as ration additives to provide omega-3 fatty acids to dairycows. Supplementing dairy cows with omega-3 fatty acid-rich feeds does not easilyincrease quantities in milk fat of ...dairy cows because polyunsaturated fatty acids arebiohydrogenated in the rumen. Lipid encapsulation of omega-3 fatty acids providesprotection from biohydrogenation in the rumen and allows them to be available forabsorption and utilization in the small intestine. Lactating cows were supplemented withrumen protected algae biomass or algal oil in a 4 à 4 Latin Square. Feeding lipidencapsulated algae supplements increased docosahexaenoic acid content in milk fat whilenot adversely impacting milk fat yield; however, docosahexaenoic acid was preferentiallyesterified into plasma phospholipid, limiting its incorporation into milk fat. In the secondstudy, triglyceride emulsions of oils enriched in either oleic, linoleic, linolenic, ordocosahexaenoic acids were intravenously infused to avoid confounding effects oftriglyceride esterification patterns in the small intestine and to compare mammary uptake.Milk transfer of fatty acids delivered as intravenous triglyceride emulsions was reducedwith increased chain length and unsaturation. Increased target fatty acids were evident inplasma phospholipid, suggesting re-esterification in the liver. Transfer efficiencies were 37.8, 27.6, and 10.9±5.4% for linoleic, linolenic, and docosahexaenoic acid. Both liverand mammary mechanisms may regulate transfer of long-chain polyunsaturates.Intracellular fatty acid binding proteins (FABP) are cytoplasmic proteins that arehypothesized to be essential for fatty acid transport and metabolism by accelerating longchainfatty acid uptake and targeting to intracellular organelles, such as the endoplasmicreticulum for triglyceride esterification. FABP3 mRNA is highly expressed in bovinemammary and heart tissue, but is not present in MAC-T cells, a bovine mammaryepithelial cell line. When overexpressed in MAC-T cells, FABP3 does not appear to berate-limiting for fatty acid uptake in vitro and did not alter lipid metabolism. The functionof FABP3 in the mammary gland remains unclear.
