Study On Nutritional Regulation Of Milk Fat Synthesis In Lactating Ruminant

This experiment aimed to regulate milk fatty synthesis by the change toward the mammary glands nutrition matter provided, and through the variety of the milk compositions and related blood compositions to study the mechanism of milk fatty depression. Mammary uptake of nutrients was estimated through assay of arteriovenous differences and blood flow measurements.Experiment one: Four ShaNeng milk goats fitted with permanent ruminal fistulae and embedded carotid under the skin are infused rumen outside about four kinds of volatile fatty acids continuously(the proportion of acetate:propionate:butyrate is:① 75:15:10; ② 65:25:10; ③ 55:35:10; ④ 45:45:10).The experiment was designed as 4×4 Latin square test. The food was given 1.5kg/d in particle and the proportion of the fine and crude is 45:55, and given every 2h. Among them, the food of one day should satisfy the demand of the sheep, the VFA that rumen infused provides the equivalent of an additional 30% of MEm.One experiment periods consisted of nine days, six days pre-infusing, three days sampling, and the interval is seven days. The result is:① The continuous infusion of VFA can change VFAs concentration and proportion in the rumen, PH is 6.56-6.74, the VFA concentration and molar ratio are changed, the total VFA lowers gradually (p<0.05). Acetic acid concentration is far high than propionate, butyrate in artery, and the mammary uptake ratio of VFAs is different . The relationship exists between the artery and the rumen of acetate, propionate,butyrate。 ② The milk yields and food intakes are little effect. With the decrease of the acetic acid in the rumen, the milk fat percent and yields descend, but Group 3 is the tallest. The lactose has no effect, the milk protein is effect between the group 2 and group 4.③ With rising of propionate in the rumen, the insulin linearly increases ((p<0.05)); the blood glucose is no effect. ④ The concentration of acetic acid, BHBA, TG in the artery that synthesize the fat acid totally expresses the different degree to decline, the NEFA rises linearly, and the group 4 is higher than theelse(p<0.05),it has no influence with TG^ BHBA.The mammary uptake ratio of the NEFA^ Acetate N BHBA and TG descend totally, the groups 1 and 2 is higher than the else for the NEFA (p<0.05 ) .The mammary uptakes of acetate linearly decrease, the group 4 is higher than group 2( p<0.05),there is no influence with TG^ NEFA.d) Milk fatty acids Ci6:o are the most, it has no difference in the experiments, the next in order is Ci8:i(cis-Ci8:i), Ci4:o, Cio:o> Ci2:o etc.With the decrease of the acetic acid concentration in the rumen, the de novo milk fatty acid synthesis increase.and the long chain fatty acids descend curvedly. Ci8:o and Cjg^curvedly decrease, and group 4 is less than group l.CLA and tl0cl2CLA decrease linearly.In conclusion, the milk goats fed the particle in the rate of the fine/crude 45:55 and infused of mixed VFA continuously can be changed of the milk fat percent and yields at the same time the fatty acid compositions, and there is some effect of insulin on the MFD, CLA and TEA have no effect on it. The conversion efficiency of the de novo milk fatty acids is higher than the long chain fatty acids by the infusion of mixed VFA in rumen.Experiment two: Two ShaNeng milk goats which embedded carotid under the skin were studied the variety of the composition of the milk and related bloods through arteriovenous differences and the hyperinsulinemic-euglycemic clamp, and to verify the mechanism about the milk fat synthesis. The experiment is to divide into 3 periods, each term 5 days. The initial interval allowed for acclimation, and baseline measurements were established during the second interval. During the third interval a hyperinsulinemic-euglycemic clamp was maintained, and insulin was infused continuously at the rate of ljig/kgBWh", and euglycemia was maintained by infusion of glucose (25% w/v) at variable rates. One side neck intravenous injects glucose and insulin , another side is blood sampling. Feed freely and food was given every 2h. The result is: The insulin has some effect on the depression of milk fat; and blood glucose slightly affect, The milk fat percent lower (p<0.05), and the milk fat yields reduces 40.44% (p<0.01).Milk protein N the milk yields andfoods intake also descend, and the lactose increase a little bit. It decreases availability of milk fat precursors in different degree, and it has very effect to TG and acetate (p<0.05). The mammary uptake ratio of butyric acid and NEFA decrease (p<0.05), the else is no significant. All the Mammary uptakes of the precursors also descend, the acetate ? NEFA and butyric acid is 23.53% (p<0.05K 48.71 %(p<0.01) and 50.57 % (p<0.05) in turn, and TG and propionate acid are not significant.Milk fatty acid compositions were modified. The short chain fatty acids (C4:o- Cg:o) descends 16.39% (p<0.05), the medium chain fatty acids (C&:o-Ck,/2) increases 6.1%, the long chain fatty acids (C16/2-C22) descends 1.72%. Trans-Ci8:1 descends (p<0.05) ,and same as CLA and trans-10, cis-12CLA .Cis-Cig:i rise 4.55%OTo sum up, for the milk goat, according to the comprehensive analysis, insulin can lower the milk fat percent and yields, and change the milk fatty acid compositions, but it is not significant. The insulin has some double function to regulate the synthesis of milk fatty acid. There is no effect of CLA and TFA on MFD.