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.

Identification of the oleic acid ethanolamide (OEA) isomer cis-vaccenic acid ethanolamide (VEA) as a highly abundant 18:1 fatty acid ethanolamide in blood plasma from rats and humans

“…In addition to oleic acid (cis9-18:1), other monounsaturated fatty acids with 18 carbon atoms (18:1) are present in common foods, namely petroselinic acid (cis6-18:1), vaccenic acid (cis11-18:1), elaidic acid (trans9-18:1), trans-petroselinic acid (trans6-18:1), or trans-vaccenic acid (trans11-18:1) [15][16][17][18]. These fatty acids can be considered as potential sources for the formation of FAEAs in vivo and could explain our observations by UHPLC-ESI-MS/MS.…”

“…Additionally, meat like mutton, veal, beef, or pork contains oleic acid as the main fatty acid [15]. In contrast, vaccenic acid is only part of few and special foods like yak milk [16] or milk products like Scamorza ewe milk cheese [17]. According to the manufacturer (Altromin, Lage, Germany), the fat content of the used rat chow consists of the indigenous fat of the processed cereals and added soy oil.…”

“…As candidates qualify the position isomers of oleic acid (cis9-18:1), namely vaccenic acid (cis11-18:1) and petroselinic acid (cis6-18:1), or the respective trans-isomers elaidic acid (trans9-18:1), trans-vaccenic acid (trans11-18:1), and transpetroselinic acid (trans6-18:1). Vaccenic acid mainly appears in milk, e.g., from yaks [16] or milk products like Scamorza ewe milk cheese [17]. Furthermore, vaccenic acid seems to influence the endocannabinoid system by reducing the plasma level of AEA in hypercholesterolemic subjects [18].…”

Postpartum oestrous cycling resumption of yak cows following different calf weaning strategies under range conditions

“…The yak ( Poephagus grunniens ) is a multipurpose ruminant which fills an important ecological and social niche on the Qinghai‐Tibetan plateau (Ding et al., ; Sarkar, Meyer, & Prakash, ). However, productivity and growth rate of yaks are low compared with cattle (Ding et al., ) and their low reproductive rate restricts yak production (Zi, ).…”

Isolation, identification and fibrolytic characteristics of rumen fungi grown with indigenous methanogen from yaks (Bos grunniens ) grazing on the Qinghai-Tibetan Plateau

“…The yaks graze on the Qinghai-Tibetan Plateau at an elevation higher than 3000 m throughout the year, and local inhabitants rely on the yaks as an important source of transportation, milk and meat (Ding et al 2013). Due to the long-term shortage of crop grains, yaks mainly live on wild grass to thrive in a harsh environment (Long et al 2008).…”