The Study Of Milk Nutrient Component And Fatty Acid Of Pastured White Yak In Tianzhu, Gansu

The milk performance of yaks with different birth,the contents of protein, fat, lactose, dry matter and ash in the yaks'milk were measured;the content of fatty acid in yaks' milk fat was tested by GC-MS.The results were compared with the counterparts of holstein,scalper. The pasture yield of alpine pasture and the nutrient component of the pasture in Tianzhu Tibetan Municipality, Gansu,were studied, too.The milk yield increased with the increase of the yaks' birth. After fifth birth; the milk yield tended to decrease; the milk yield of third to fifth birth yaks in Nannigou pasture was significantly higher than that of their congener in Daiqian pasture and Wushaoling pasture (P<0.05) ,and the mean milk yield of the former in July and August was higher than that of the two later;the pasture production in Nannigou was higher than those in Daiqian and Wushaoling .The higher milk performance of yaks in Nannigou was attributed to the higher pasture production in the pasture.The contents of fat and protein in yaks' milk from the 3 pastures were not significantly different(P>0.05 ),while the contents of fat and protein in yaks' milk were exetremly significantly higher than those of Holstein milk(P<0.01).The contents of fatty acids in yaks' milk from the 3 pastures were not significantly(P>0.05),indicating that the conditions of the pasture have no effect on the contents of fatty acid in yaks' milk.The contents of fatty acids in milk of 1 to 5 birth yaks were not significantly different(P>0.05),showing that the different birth yak has the same physiological mechanism of synthesizing fatty acid.Contrasted with the contents of fatty acids of Holstein milk,the contents of unsaturated fatty acids(USFA) in yaks' milk were significantly higher(P<0.05) and the contents of saturated fatty acids(SFA) in yaks' milk were significantly lower(P<0.05),resulting from different genes and feeding patterns.The contents of SFA and USFA and the ratio between SFA and USFA were 65.05%,34.95% and 1.86 in fading period. The contents of SFA and USFA and the ratio between SFA and USFA were 63.61%,36.39% and 1.75 in end of fading period. The contents of SFA and USFA and the ratio between SFA and USFA were63.09%,39.02% and 1.62 in buding period. The contents of SFA and USFA and the ratio between SFA and USFA were56.96%,43.04% and 1.32 in flourishing period.With the rising of temperature and the mature of pasture,the contents of SFA in yaks'milk were declining while the contents of USFA were increasing.