Effects Of 2-hydroxy-4 (Methylthio) Butanoic Acid Isopropy Ester On Production Performance Of Cashmere Goats,and The Amino Acid Transporter Genes Expression Of Sucking Lambs

The objective of this experiment was to investigate the effect of dietary 2-hydroxy-4-(methylthio)butanoic acid isopropyl ester(HMBi)supplemental levels on production performance and amino acids metabolism of lactating ewes and sucking lambs.The study could provide a reference for the use of HMBi on goats.On this basis,it was amid to explore the expressions of several sulphur amino acids transporters gene SLC3A2,SLC38A2,SLC1A5 and SLC6A19,in order to provide the theoretical basis for the molecular mechanism of absorbtion,transportation and utilization of amino acids.Twenty seven healthy lactating Shaanbei White Cashmere goats with similar body weight(49.79±1.86 kg)were selected and randomly assigned to 3 groups with 3 replicates in each group,and each replicate contained 3 ewes and 3 lambs.The control group was fed the basal diets,while 2% and 4% HMBi was added respectively in the test groups.The experiment included a pretral period of 10 days and an experimental period of 60 days.Average daily gain,cashmere quality of ewes and lambs,and milk composition,serum biochemistry indices,plasma and milk amino acid content of ewes were measured.At the last day of trial,one lamb in each replicates were butchered,collected tissues of skin,liver,duodenum,jejunum and ileum.Primers were designed according to the sequences of SLC3A2,SLC38A2,SLC1A5 and SLC6A19 cDNA of goat in GenBank.Those genes' s relative expressions were quantified by Real-time Quantitative PCR(RT-QPCR),and then analysis their expression pattern in 5 tissues above.Main results showed that as follows:1.Supplement HMBi in diet could ease the weight loss of ewes during lactating period.The average daily gain(ADG)of ewes in 2% group was significantly higher than those in control group(P<0.05);Supplement HMBi in ewes' s diet could increase the average daily gain of lambs,and the ADG of lambs in 4% group was significantly higher than those in control group(P<0.05).2.1)With the increasing of dietary HMBi levels,the wool length and growth rates of ewes increased,but there was no effect on cashmere diamater(P>0.05);The dietary HMBi levels of ewes had no significant effect on hair length,diameter and growth rates of suking lambs(P>0.05);2)The milk fat percentage,milk protein percentage,milk total solid content,and solid not fat content of ewes in 4% group were significantly higher than those in control group(P<0.01);The content of methionine,essential amino acids and total amino acids in milk of test groups had a increasing trend;3)The serum urea nitrogen content of ewes in 4% group was significantly lower than those in control group(P<0.05),plasma Met content of ewes in 4% group was significantly higher than those in control group(P<0.05).3.The expressions of SLC3A2 in skin and SLC1A5 in jejunum have significant difference among three groups(P < 0.05),but there was no significant difference on expressions of SLC38A2 and SLC6A19 among different groups(P>0.05).4.The expression pattern showed as follows: In the different tissues,the expressions of 4 genes were highest in liver,but lowest in skin;In different segments of small intestine,the expressions of SLC3A2 were highest in duodenum,then in jejunum and ileum;The expressions of SLC38A2,SLC1A5 and SLC6A19 were highest in jejunum,then in duodenum and ileum.In conclusion,supplement HMBi in diet could improve the growth performance and cashmere quality of lacting cashmere goats,and increase the growth performance of sucking lambs,but have no significant influence on cashmere quality and the expressions of several sulphur amino acids transporters gene.According to the organizational difference of amino acids transporter genes' s expressions,we supposed that neutral amino acids in small intestine are mainly absorbed in duodenum and jejunum.Besides,liver may be a relatively active place for amino acid metabolism.