季节性放牧对牧草、牦牛瘤胃液和乳脂中脂肪酸组成的影响及其关联分析

Effects of Seasonal Grazing on Fatty Acid Composition in Forage,Yak Rumen Fluid and Milk Fat and Their Correlation Analysis

本研究旨在探讨季节性放牧对牧草、牦牛瘤胃液和乳脂中脂肪酸组成的影响。选取20头带犊大通泌乳牦牛[体重(251.5±10.5) kg],在春季(4—6月)、夏秋季(7—9月)、冬季(10—12月)连续9个月放牧。采集春季、夏季和冬季3个放牧季节牧草、放牧牦牛瘤胃液和常乳,测定和分析牧草、瘤胃液和乳脂中脂肪酸组成和含量。结果显示:夏季牧草中粗蛋白质、肉豆蔻酸、棕榈酸、c9油酸、c9t11共轭亚油酸、t10c12共轭亚油酸、总共轭亚油酸和多不饱和脂肪酸含量显著高于春季、冬季(P<0.05),春季显著高于冬季(P<0.05)。夏季放牧牦牛瘤胃液中乙酸、丁酸、异丁酸、总挥发性脂肪酸、t11油酸、c9t11共轭亚油酸、t10c12共轭亚油酸、总共轭亚油酸和多不饱和脂肪酸含量显著高于春季、冬季(P<0.05),春季显著高于冬季(P<0.05)。夏季放牧牦牛乳脂中乳蛋白、乳脂、全乳总固体、非脂乳固体、乳糖、酪蛋白含量和酸度显著高于春季、冬季(P<0.05),春季与冬季差异不显著(P>0.05);夏季放牧牦牛乳脂中油酸、亚油酸、c9t11共轭亚油酸、t10c12共轭亚油酸、总共轭亚油酸以及多不饱和脂肪酸含量显著高于春季、冬季(P<0.05),春季显著高于冬季(P<0.05)。综上所述,夏季牧草、放牧牦牛瘤胃液和乳脂中总共轭亚油酸和不饱和脂肪酸含量最高,冬季最低,建议选择夏季进行放牧,在冬季则对放牧带犊大通泌乳牦牛进行合理补饲,以保证有较高品质的乳脂供应。

The purpose of this study was to investigate the effects of seasonal grazing on the composition of fatty acids in forage,yak rumen fluid and milk fat. Twenty Datong lactating yaks[body weight(251. 5 ±10.5)kg]with calves were selected to graze for 9 months. The forage,rumen fluid and normal milk of grazing yaks in spring(April to June),summer(July to September)and winter(October to December)were collected,respectively. The composition and contents of fatty acids in forage,rumen fluid and milk fat were determined and analyzed. The results showed that the contents of crude protein,myristic acid,palmitic acid,c9-oleic acid,c9t11-conjugated linoleic acid,t10c12-conjugated linoleic acid,total conjugated linoleic acids and polyunsaturated fatty acids in forage in summer were significantly higher than those in spring and winter(P<0.05),and those in spring were significantly higher than those in winter(P<0.05). The contents of acetic acid,butyric acid,isobutyric acid,total volatile fatty acids,t11-oleic acid,c9t11-conjugated linoleic acid,t10c12-conjugated linoleic acid,total conjugated linoleic acids and polyunsaturated fatty acids in rumen fluid of grazing yaks in summer were significantly higher than those in spring and winter(P < 0. 05),and those in spring were significantly higher than those in winter(P<0.05). The contents of milk protein,milk fat,total milk solids,nonfat milk solids,lactose,casein and acidity in milk fat of grazing yaks in summer were significantly higher than those in spring and winter(P < 0. 05),but there were no significant differences between spring and winter(P>0.05). The contents of oleic acid,linoleic acid,c9t11-conjugated linoleic acid,t10c12-conjugated linoleic acid,total conjugated linoleic acids and polyunsaturated fatty acids in milk fat of grazing yaks in summer were significantly higher than those in spring and winter(P<0.05),and those in spring were significantly higher than those in winter(P<0.05). To sum up,the contents of total conjugated linoleic acid and unsaturated fatty acids in forage,rumen fluid and milk fat of grazing yak in summer are the highest and in winter are the lowest. It is suggested to graze in summer and reasonably supplement grazing Datong lactating yaks with calves in winter to ensure high-quality milk fat supply.[Chinese Journal of Animal Nutrition,2022,34(5):3046-3055]