Effects Of Alpha Lipoic Acid On Sheep Production Performance,blood Biochemical Indices,glucose Metabolism,and Immune To Heat Stress

To investigate the effects of α-lipoic acid on sheep performance,glucose metabolism,biochemical indices and immune responses to heat stress.15 sheep aged 4 to 5 months weight between 35 to 40 kg were randomly selected,and equally divided into three groups:the control group(CTL),the low-dose LA supplement group(LA-L,supplemented with 600 mg/kg α-LA),and high-dose LA supplement group(LA-H,900mg/kg α-LA)was added.The diet was 7 days for the experimental factors and 33 days for the formal trial.Each test sheep was placed in a homemade metabolic cage.After 7 days of adaption,the sheep went into the formal experiment period of 33 days from July to Agust in summer with the temperature-humidity index up to 72,which was considered in the heat stress.The initial body weight for each group was determined by the average of three consecutive days weighing before 7:00 a.m.when the sheep were not fed.During the test,the sheep were weighed once every two weeks.In the middle of the experiment,blood sample were collected and plasma and serum were extracted to test biochemical indices.At the end of theexperiment,the sheep were slaughtered,dressing percentage and liver samples were collected to test various tissue indicators.The test results are as follows:1)The feed intake and daily gain of sheep increased after lipoic acid addition(0.05<P<0.1).Feed dry material intakes of LA-L and LA-H were increased by 7.6%and 2.5%respectively compared to the control group;daily gain of LA-L was increased by 11.2%compared to the control group(P<0.05).2)The feeds energy intake in the lipoic acid groups were increased,and the energy intake of LA-H was increased by 7.95%more than that of the control group(P>0.05).The energy deposition rate of LA-L was 10.36%higher than that of CTL.The difference in nitrogen deposition rate was not significant between the groups.The digestibility and utilization rates of calcium and phosphorus were increased with a trendency(0.05<P<0.1).3)From the blood biochemical indices,plasma ALT and AST in α-LA addition groups were decreased,and LA-H group was significantly lower than that of CTL group(P<0.05).Blood urea level in LA-L and LA-H group were also decreased compared with CTL group,but it was not different significantly.Glucose,cholesterol,triglyceride and low density lipoprotein were all decreased in LA-L and LA-H,but there was no significant difference with CTL(P>0.05).4)The metabolic changes were also reflected in metabolomics.Through the LC-MS detection and analysis of sheep serum samples,there were 1294 characteristic metabolites were detected from the serum.Analyzed difference using statistics(P<0.05)combined with PC A(VIP>1)as well as OPLS-DA,20 characteristic differential metabolites in posstive modeland 17 differential metabolites in the negative model were found,these metabolites were located in the glucose,amino acids and lipid metabolic pathway,showed that α-LA closely connected with nutrition metabolism.5)α-LA affected glucose metabolism was also find in molecular level.the mRNA expression of G6PC in the lipoic acid treatment group was significantly lower than that in CTL,and PEPCK1,FBP1,and ACSS3 all decreased,but there was no significant difference with CTL;PCB was increased.At the protein level,the expression levels of G6PC and PEPCK1 were significantly reduced in α-LA group.6)There is a great immune response with the addition of α-LA,immune globulin IgG,IgA were all increased.Immune related cytokines were changed,proinflammatory cytokines,such as IL-1β and TNFα in the LA groups were decreased,so did the inflammatory cytokine of IL-8(P<0.05),but the IL-6 did not change significantly.On the other hand,IFN-γ,an anti-inflammation and immune regulatory cytokine increased significantly(P<0.05).The similar it was in the molecular level,the mRNA expression of IL-1β,IL-8 and NF-κB were significantly decreased;IFNγwere significantly increased.The immune response of sheep was increased.7)As for the antioxidation ability,GR and SOD(P<0.05)level in α-LA addition groups were increased,and the harmful oxidation production MAD were significantly decreased(P<0.05).Under heat stress in sheep,α-LA increased the blood and liver HSP70 expression level dramatically.At the protein level,the expression levels of HSP70 and HSF1 were significantly increased in α-LA group.