Effects Of Rumen-Protected Leucine And Rumen-Protected Methionine On Production Performance And Negative Energy Balance Of Dairy Goats In The Postpartum Period

Lactation initiation significantly increases the nutritional requirements of dairy animals,and the reduction in dry matter intake before and after calving makes periparturient dairy animals highly susceptible to a negative nutritional balance.Highly productive dairy cows call up to 1 kg/d of tissue protein from skeletal muscle during the first 7-10 days of lactation to meet the amino acid requirements of lactation.In fact,somatic tissue mobilization begins prior to parturition to meet amino acid requirements for fetal,uterine and mammary tissue growth.Therefore,maximizing the energy requirements of dairy animals during the perinatal period is essential for a smooth perinatal transition.The metabolic status of perinatal nutrition affects the postpartum and even lifelong lactation performance of dairy animals.Our group showed that per-rumen methionine can effectively improve liver function and hepatic gluconeogenesis in periparturient dairy cows and maintain their health;functional amino acid(leucine)can stimulate pancreatic α-amylase secretion in adult cows and sheep,promote small intestine starch digestion and increase energy supply.The aim of this study was to investigate the effects of per-ruminal leucine and per-ruminal methionine on the production performance and negative energy balance of periparturient dairy goats,to comprehensively evaluate the supplementary effects of per-ruminal leucine and per-ruminal methionine and their mechanisms,and to provide a theoretical basis for production applications.Experiment 1 Effects of rumen-protected leucine and rumen-protected methionine on performance and milk quality of dairy goats during the late perinatal periodSixty first-parturition and late perinatal dairy goats were randomly divided into 4groups: control group(CON): feeding basal diet;Rumen-protected leucine group(RPL):basal diet + 5 g/d rumen-protected Leucine(amount to small intestine,same below);Rumen-protected methionine group(RPM): basal diet + 5 g/d rumen-protected methionine;Rumen-protected leucine and rumen-protected methionine mixed group(RP(L+M)): basal diet + 5 g/d rumen-protected leucine + 5 g/d rumen-protected methionine.Rumen-protected leucine or rumen-protected methionine was supplemented from postpartum day to postpartum day 21.After 21 days,all the sheep in the large group were uniformly fed to the large group.Body weight was measured on 0 d,7 d,21 d,and 90 d after delivery.The milk yield of each animal was calculated on 7,14 d,21 d,50 d,70 d,and 90 d.Milk samples were collected on day 21 to detect milk composition,and the daily feed intake of each animal was recorded twice a week during the addition period.It was observed that the addition of RPL and RPM had no effect on feed intake,body weight,milk production and milk composition of dairy goats,but tended to improve lactation efficiency;RPM significantly improved milk production and increased body milk protein,lactose and total solids production in dairy goats.Therefore,both RPL and RPM could improve production performance.Meanwhile,there was an interactive effect on the regulation of milk protein.Under the present experimental conditions,RPM improved the postpartum performance of dairy goats better than RPL.Experiment 2 Effects of rumen-protected leucine and rumen-protected methionine on blood biochemical indices of dairy goats during the late perinatal periodBased on experiment 1,jugular vein blood samples of all sheep were collected before morning feeding on the 7 d,14 d,and 21 d after delivery to detect blood biochemical indices.The results showed that RPL reduced plasma NEFA,TG,GSH-Px,SOD and T-AOC,increased plasma VLDL and MDA,and had no effect on plasma BHBA,TBIL,ALT,AST,ALB and TP;plasma Lys decreased and Met and Cys increased.RPM decreased plasma NEFA,TG and ALT,increased plasma VLDL and BHBA,and had no effect on plasma TBIL,AST,ALB and TP;increased plasma Val and Asp,and decreased plasma Thr and His.Except for the interaction effect of plasma Val and Hyd levels,RPL and RPM had no reciprocal effect on other biochemical parameters of plasma.The addition of RPL and RPM could regulate lipid metabolism,change plasma amino acid composition and reduce plasma antioxidant capacity in perinatal dairy goats;RPL had no effect on liver function,while PRM could enhance liver function;there was no reciprocal effect between RPL and RPM in regulating lipid metabolism and liver function,and RPM was stronger than RPL in alleviating perinatal NEB.RPL improves milk production efficiency by regulating liver lipid metabolism and altering plasma amino acid composition in dairy goats;RPM improves lactation performance by regulating periparturient lipid metabolism,enhancing liver function and altering plasma amino acid composition in dairy goats.RPL and RPM had no reciprocal effects in regulating lipid metabolism and liver function,and RPM was more effective than RPL in alleviating periparturient NEB.both of them decreased the plasma antioxidant fraction in dairy goats,which may be associated with higher production performance.