title: Seasonal variations in the fatty acid profile of milk from yaks grazing on the Qinghai-Tibetan plateau.
abstract: An experiment was conducted to study the seasonal changes in the fatty acid profile of milk from yaks (Bos grunniens) when kept at altitudes of 3000 m above sea level (a.s.l.) and higher. Data and samples were collected in summer (July), autumn (September), winter (November) and spring (March) from ten lactating yaks (four in spring). The yaks grazed pastures adjacent to the farm building throughout the year. In spring only they received 0·6 kg crop by-products per day (dry matter basis). Fresh alpine grasses, available in summer and autumn, showed high concentrations of α-linolenic acid (46-51 g/100 g lipids) compared with the dry, yellow vegetation of winter and spring (16 g/100 g lipids). In autumn and summer, the milk fat had higher concentrations of polyunsaturated fatty acids than in winter. These polyunsaturated fatty acids were comprised of vaccenic acid, rumenic acid and α-linolenic acid, which are all considered beneficial to human health. The rare fatty acid, γ-linolenic acid, was also detected in yak milk, especially in the milk obtained in spring. The results suggest that yak milk, which is the most important basic food of the Tibetan herders, has the most favourable fatty acid profile when yaks grazed green pasture, which also corresponds to the period of highest milk production.
authors.affiliation: State Key Laboratory of Grassland Agro-Ecosystem, Institute of Arid Agroecology, School of Life Sciences, International Centre for Tibetan Ecosystem Management, Lanzhou University, Lanzhou 730000, PR China.
authors.forename: Luming
authors.initials: L
authors.lastname: Ding
authors.forename: Yupeng
authors.initials: Y
authors.lastname: Wang
authors.forename: Michael
authors.initials: M
authors.lastname: Kreuzer
authors.forename: Xusheng
authors.initials: X
authors.lastname: Guo
authors.forename: Jiandui
authors.initials: J
authors.lastname: Mi
authors.forename: Yujiao
authors.initials: Y
authors.lastname: Gou
authors.forename: Zhanhuan
authors.initials: Z
authors.lastname: Shang
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.forename: Jianwei
authors.initials: J
authors.lastname: Zhou
authors.forename: Hucheng
authors.initials: H
authors.lastname: Wang
authors.forename: Ruijun
authors.initials: R
authors.lastname: Long
mesh_terms: D000531:Altitude; D000822:Animal Husbandry; D000818:Animals; D002417:Cattle; D005227:Fatty Acids / Q000737:chemistry; D005260:Female; D008892:Milk / Q000737:chemistry*; D012621:Seasons
chemical_list: D005227:Fatty Acids