Chemical and Fatty Acids Composition of Yak Milk from Qinghai-Tibetan Plateau in Different Seasons

Background: Yak milk is the main source of dietary protein, fat and micronutrients for Qinghai-Tibetan Plateau residents. However, few studies have focused on the seasonal variation of nutritional components in natural grazing (without supplementary feeding) yak milk. Methods:Yaks living at high altitudes (average altitude of more than 4200 metre) were selected (summer, n=18; winter, n=18; spring, n=15) to analyzed seasonal influence on chemical and fatty acids composition of yak milk. Result: Results showed that the contents of fat, protein, lactose, non-fat milk solid, vitamin A and the main fatty acids (C6:0, C12:0, C14:0, C15:0, C16:0, C17:0, C20:0, cis-9 C16:1, cis-9 C18:1, trans-9 C18:1, LA, etc.) in winter yak milk were significantly different from those in summer and spring yak milk (p less than 0.05). This suggests that chemical and fatty acids composition of yak milk were influenced by seasons.