Fatty Acid Profile in Milk Fat from Qinghai Plateau Yak at Different Altitudes and Parities1

Qinghai Plateau yak are the most important grazing livestock for milk and beef production on the Qinghai-Tibetan plateau because they are adapted to extremes of cold environment and higher elevation and can be grazed throughout the year. Milk samples (n = 47) from Qinghai Plateau yak cows of different parities and milk samples (n = 6) from Qinghai yellow cattle cows were analyzed using gas chromatography-mass spectrophotometry. Differences in fatty acid profiles of Qinghai Plateau yak milk fat from rangelands at 3 different elevations, at 2 parities, and between species were compared. Additionally, fatty acid profiles of forages from different elevations were analyzed. Fatty acid percentages (g/100 g total fatty acids) in milk fat of Qinghai Plateau yak from different rangelands were largely similar, but there were differences (P < 0.05) in individual fatty acids, including conjugated linoleic acid. There were also elevation differences in fatty acid percentages (e.g., cis-9, cis-12 C18:2 and cis-9, cis-12, cis-15 C18:3; g/100 g total fatty acids) of forage plants. Milk from multiparous Qinghai Plateau yak cows showed greater (P < 0.01) percentages of C18:1 and C18:2, total unsaturated fatty acids, total monounsaturated fatty acids, and total polyunsaturated fatty acids and lesser (P < 0.01) percentages of total saturated fatty acids than primiparous counterparts. The cis-9, trans-11 conjugated linoleic acid isomer percentage in milk fat from multiparous cows was greater (P < 0.01) than from primiparous cows. The study results also suggested that short-chained, medium-chained, and saturated fatty acid percentages of milk fat were greater (P < 0.05) for Qinghai Plateau yak compared with those of Qinghai yellow cattle.