CHANGES IN PLASMA AMINO-ACID PATTERNS AND WOOL GROWTH IN RESPONSE TO ABOMASAL INJECTIONS OF AMINO-ACIDS DURING LATE PREGNANCY AND EARLY LACTATION

Provision of sulfur-containing amino acids into the abomasum has incre ased wool production in non-reproducing sheep and, on the basis of suc h studies, they have generally been considered as the primary limiting nutrients for wool growth. The specific amino acid needs of reproduci ng ewes were investigated in the current study. Three groups of pregna nt ewes were fitted with temporary abomasal fistulae. For the last 3-4 weeks of pregnancy and the first 3 weeks of lactation, solutions cont aining sodium hydroxide (as a carrier) or methionine or a mixture of v aline, arginine, lysine and threonine (VALT) were injected into the ab omasum twice per day. The injection of methionine did not increase pro tein deposition during pregnancy; this was indicated by the failure of the treatment to lower the concentration of other amino acids in plas ma, or increase liveweight, lamb birth weight or wool growth. Response s in early lactation were different with the methionine injected sheep having a lower concentration of free lysine, valine, alanine and seri ne in plasma, indicating an increased rate of protein deposition, and a faster growth rate in the ewes. Injections of VALT caused a decrease in the concentration of cystine and methionine in plasma and depresse d wool growth and tensile strength. The results indicate that a lack o f methionine was not limiting protein deposition during late pregnancy , but may have been during early lactation. Valine, arginine, lysine a nd threonine were not the primary limiting amino acids in late pregnan cy or early lactation.