Comparative Study of Nutrient Composition of Yak Milk from Qinghai Plateau Yak in Different Seasons

This study analyzed the effect of season on the nutrient and fatty acid composition of yak milk. Yak milk samples from the Qinghai-Tibet Plateau in summer and winter (n = 18, each) were selected for this study. Results showed that the contents of protein, lactose, non-fat milk solid, ash, vitamin A and main trans fatty acids (trans-9 C_18:1 and trans-9,12 C_{18:2 n-6}) were significantly lower in winter than in summer (P < 0.05), while the contents of fat and main fatty acids (C_16:0, C_17:0, C_18:0, cis-9 C_16:1, cis-9 C_18:1 and cis-9,12 C_{18:2 n-6}) in yak milk were significantly higher in winter than in summer. This suggests that the nutrient and fatty acids composition of yak milk from the Qinghai-Tibet Plateau are influenced by season.