Responses in splanchnic and mammary amino acid metabolism to short-term graded removal of methionine in lactating goats  

作　　者：Yantao Li Mark D.Hanigan Xueyan Lin Zhiyong Hu Zhengui Yan Qiuling Hou Yun Wang Zhonghua Wang 

机构地区：[1]Ruminant Nutrition and Physiology Laboratory,College of Animal Science and Technology,Shandong Agricultural University,Tai'an 271018,China [2]Department of Dairy Science,Virginia Tech,Blacksburg 24061,USA

出　　处：《Animal Nutrition》2023年第2期116-125,共10页动物营养（英文版）

基　　金：National Natural Science Foundation of China under project number 31772623 and by China Agriculture Research System of MOF and MARA.

摘　　要：Four multi-catheterized lactating goats were used in a 4×4 Latin square experiment to investigate the responses of amino acid metabolism in portal-drained viscera(PDV),liver,and mammary glands to short-term varying supplies of methionine(Met).During the last 45 h in each experimental period,goats were fasted for 12 h and then abomasally infused with an amino acid(AA)mixture plus glucose for 33 h.Treatments consisted of graded removal of Met from an infused AA mixture to achieve Met content in the infusate of 100%(complete),60%,30%,or 0%that in casein.Graded Met removal decreased the pro-duction of milk,milk protein,lactose,and fat linearly whilst also decreasing arterial Met concentration linearly(P<0.05).Meanwhile,net PDV uptake and liver removal of Met decreased linearly(P<0.05)due to decreased Met affinity of PDV and liver(P<0.05).Net mammary uptake of Met(P>0.1)was maintained as Met supply declined.This was achieved through increased mammary affinity(P<0.05)and increased mammary blood flow(P<0.05)totally offsetting the negative effect of decreased circu-lating Met concentration.Graded removal of Met from the infusate linearly decreased mammary uptake-to-milk output ratios of Met(P<0.05)and tended to decrease essential amino acid(EAA)linearly(0.05<P<0.1).Treatments also linearly decreased circulating concentration of prolactin and linearly increased insulin concentration(P<0.05).In conclusion,results of the present study indicated there were several mechanisms used to mitigate a Met deficiency,including reduced catabolism of Met in PDV,liver,and peripheral tissue(including mammary glands)and a linear increase in mammary blood flow.The observed decreases in milk protein production as Met supply decreased appear to be a result of regulatory events which may have been driven by decreased circulating prolactin,rather than as a result of decreased mammary Met uptake.

关 键 词：METHIONINE Lactating goat Milk protein Amino acid Splanchnic tissue 

分 类 号：S827[农业科学—畜牧学]