Effects On Mammary Metabolism And Productivity In Lactating Goats When One Essential Amino Acid Limits Milk Production

Lactation processes employ the priority to utilize the plasma AA, we use this theory to provide limited AA of lactation. In this way, AA extraction by the mammary gland from blood may be maximized. The aim of this study was to detect and analyse amino acid (AA) absorption and metabolism of the mammary gland in response to an imposed limitation on Lys(-L), Arg(-A), Met(-M) or His(-H) supply for milk production by nutrients infusion technique, arterio-venous technique and flow probes monitor technique.Three nonpregnant, multiparous lactating British Saanen goats (40±5 kg of BW) were used. Under general anesthesia, a catheter was placed into the abomasum,the carotid artery was elevated to a subcutaneous position, the common collateral vessels between the udder halves were ligated, and an ultrasound flow probe was positioned around the external pudic artery (EPA). In two 3×3 complete Latin Square designes(-L and–A; -M and -H), lactating goats were fed a low protein ration that provided only 100% of metabolizable protein and energy requirements for maintain. The protein and energy of milk production was alleviated by infusion into the abomasum of an AA mixture (full AA or excluding one AA) and ripe corn starch. Goats were assigned to treatments (8 to 10 d) according to the design. On the three days of the sampling period, arterial and mammary vein blood were withdrawn to determine blood AA concentration(10ml/30min). Flow probes monitored mammary blood flow. The results showed that low levels of blood EAA were: 1) yields of milk, CP(milk N×6.38) and CP (milk N×6.25) content significantly reduced (p<0.05) in the group of -M and -H. But these had no deference in the group of -L and -A; 2) mammary blood flows increased by 46.7%, 101.5%, 61.1% and 41.3%; 3) Extraction rates of free AA by mammary gland during–L, -M and–H increased by 39.7%,139.9%,31.3%, especially the grop of -M and-H (p<0.05). But it had no deference in -A; 4) arterial and venous blood concentration lower (p<0.05) except–A. But mammary uptake changed little. Mammary gland may attempt to overcome an AA deficiency by controlling MBF and extraction.?This method of the study can be used for the research of ideal AA during lactation in ruminant animals.