Effect Of Dietary Supplementation With Glutamine On Immune Performance, Cecum Microbiome And Skeletal Muscle Of Young Rex Rabbits

RexRabbit is a kind of small-typeherbivorous mammalwith high economic value which could both use for its fur and meat. Young Rex Rabbits during 1~2 months after weaningshoweda low immunity and easier to get various diseaseleading to many adverse effectson its health and performance. Glutamine hasprovedto be a conditional essential amino acid which playedvery important roles in anti-stress, immunityenhancing, tissue repairing and muscle growing under disadvantageousbody conditions,itcan be used as an ideal green feed additive.Theeffectofdietarysupplementationwithdifferentlevelsofglutamineon immune performance andcecummicrobiomeand muscle development were estimated on young RexRabbit.The feeding trial lasted 60 days(phase I:0 d-30 d; phase II: 31 d-60 d) after a 7-day-pertrial. A total 240 RexRabbitson 35-day-old after weaning were random assignedinto6groups(40replicates,1rabbitperreplicate) and fedwithbasaldietby adding0,0.4%,0.8%,1.2%,1.6%, 2.0%glutaminerespectively.Sixrabbitsfromeachgroupweresla ughtered on 30dand60 dforsampleanalyzing to determine the effect ofimmuneorgan index, Igs and GSH content in serum, MUC1 and MUC2geneexpressioninileummucosa, the normal flora amount in cecum.Muscle developmentwas analyzedon 60 d.Resultshowedthat:1. AddingglutamineindietcouldimprovetheimmuneorganindexandserumIgAandGSHvalueofyoun gRexRabbitsignificantly(P<0.05)orverysignificantly(P<0.01)inbothtwophasesinadose-dependentmanner.However,nullassociationwasfoundinseru mIgMcontent(P>0.05)whileasignificantlydecreasedtrend(P<0.01)waspresentedinIgGcontent.TheMUC1 and MUC2geneexpressioninileummucosa of control group were both abnormal increasedsignificantly(P<0.01) in phase I. MUC1 increased with glutaminelevelinacertainrange in phaseII, while MUC2expressionwasnotinfluencedbyglutamine(P>0.05).The best adding level ofglutamine for phase I was 1.6%while0.8% was the best for phase II.2. Diet add glutamine could obviously improve the cecum flora quantity and structureof young RexRabbit in two phases, increased the frequency of beneficial advantage bacteriumlikeRuminococcus albus,Alistipes(P<0.05), while reducing the numbers of Clostridium and Escherichia coli(P<0.05 or P<0.01)which have an potential pathogenicity,thereby maintain a balance of the caecum microbiome.However,no significantchange was found intotal bacteria(P>0.05).The best adding level of glutamine for phase I was 1.6% while 0.8% was the best for phase II.3. The diet to add a certain level of glutamine could regulatedthe related gene expression in skeletalmuscle cells, increase IGF-I, IGF-II and FASNgene expression(P<0.05 or P<0.01) whileinhibited MSTNgene expression(P<0.01), result in apromoting effect on skeletal muscle development. So, with the increasing of the glutamine addedin diet, the densities of skeletal muscle showed a rising trend while the fiber diameter and the proportion of muscle and sarcoplasmdecreased at the same time.In summary,dietarysupplementationwithglutaminecouldobviouslyimprovetheimmuneperformanc eoftheyoungRexRabbit and enhance ilealmucosalimmunity.For cecum bacteria floras, glutamine can effectively reduce the frequency of pathogens, increasedthe probioticsfrequency, thereby enhancing the young rabbit digestive performance, advantageous to keep the young rabbits’ healthy under stress conditions. Moreover, itcould also promote the development of muscle fibers, improving the quality of musclesthrough regulated the expression of related genes in muscle cells. Consideredall health indicators,the appropriatedietsupplement level of glutamineduring the first month after weaningis 1.6%,whichishigherthan0.8%inthe second month after weaning.