Milk fatty acid profile of cows grazing elephant grass BRS Kurumi pasture with and without energy supplementation

Abstract

This study evaluated the effects of energy supplementation on the intake and milk fatty acid composition of cows grazing BRS Kurumi elephant grass pasture during the rainy season. Two treatments (with and without supplementation) were evaluated using a switchback design with six Holstein × Gyr dairy cows after the peak of lactation. The average milk yield, body weight, and days in milk of the cows at the beginning of the study were 18.0±2.89 kg day^−1, 560±66 kg, and 99±12, respectively. The evaluations were performed over three grazing cycles, with adaptation periods of 14 days and six days of sampling. In the energy supplementation treatment, each cow received 3 kg day^−1 of ground corn (as-fed basis), with 2 kg day^−1 at the morning milking and 1 kg day^−1 at the afternoon milking. The ground corn presented 87.5% dry matter, 7.3% crude protein, 5.1% ether extract, and 85% of total digestible nutrients. The cows supplemented with ground corn consumed more oleic (+567%) and linoleic (+88%) acids. Unsupplemented cows consumed 26% more α-linolenic acid and produced milk with more oleic (+10%), vaccenic (+23%), and rumenic (+21%) acids, and less (−7%) pro-atherogenic fatty acids (lauric + myristic + palmitic acids). Milk fat from unsupplemented cows showed better nutritional quality, with lower atherogenicity and thrombogenicity indices and a higher hypo/hypercholesterolemic fatty acid ratio.