Effect Of Nisin On Growth Prformance,Aastrointestinal Fermentation And Microbiota In Fatting Hu Lambs

Antibiotics are effective growth promoter for ruminant.However,issues of bacterial resistance and antibiotic residue affect ecological environment and animal food safety,and then endanger human health.Therefore,antibiotics have been baned to use for non-therapeutic purposes in China in 2020,and it has become urgent to find a non-antibiotic alternatives.Our previous in vitro study revealed the microbial mechanism of nisin(NIS)substitution for monensin(MON)in regulating rumen fermentation,but in vivo experiments have shown that low-dose of NIS did not affect rumen fermentation and microbiota in Hu lambs.Hence,higher dose of NIS was selected in this study,and MON was used as a positive control,to further verify the effectiveness of NIS on gastrointestinal tract fermentation and microbiota in Hu lambs.This study is divided into the following three parts:1 Effect of nisin on growth performance,nutrient digestion and plasma metabolites in fatting Hu lambsThis trial was conducted to evaluate the effects of high-dose of NIS substitution for antibiotics on growth performance,nutrient digestion and plasma metabolites in fatting Hu lambs.Thirty-six three-month-old male Hu lambs(23.5 ± 1 kg)were blocked by body weight(BW)into two blocks(low BW and high BW).Lambs within each block were then allotted to 9 pens respectively(two lambs/pen).Pens within each block were randomly assigned to one of three dietary treatments: negative control(NC,basal diet),positive control(40 mg of MON/kg of feed),and NIS group(274.5 mg of NIN/kg of feed).The feeding trial was conducted for eight weeks,with the first week for adaptation followed by seven weeks of dietary treatment.The results showed that ADG,DMI and G: F was not affected in three group(P ≥ 0.37).Compared with control,the NIS-fed lambs had lower EE intake(P < 0.01).No effect of NIS and MON was found on DM digestibility,OM digestibility,NDF digestibility and ADF digestibility(P ≥ 0.31).Lambs receiving NIS and MON had lower EE digestibility compared with NC(P < 0.01),but CP digestibility was higher in MON-fed lambs than in those fed NIS(P < 0.05).NIS and MON supplementation had no impact(P ≥ 0.08)on plasma alkaline phosphatase,aspartate aminotransferase,alanine aminotransferase,blood ammonia,creatinine,uric acid,total bile acid,triglyceride,total protein,albulin,globulin,glucose,while total cholesterol was higher in the MON-fed lambs(P < 0.05).Overall,lambs receiving NIS and MON reduced EE digestibility,but the growth performance and fitness was not affected.2 Effect of nisin on rumen fermentation and microbiota in fatting Hu lambsAt the end of the experimental period,one lamb was randomly selected from each units,and slaughtered for rumen contents collection.This trial was conducted to evaluate the effects of NIS subsitiution for antibiotics on rumen fermentation and rumen microbial community structure of Hu lambs.Compared with control,MON significantly increased rumen p H and reduced concentrations of ammonia,total VFA,acetate,butyrate and valerate(P < 0.05).In contrast,NIS had no effect on rumen fermentation parameters(P ≥0.05).Quantitative real-time PCR showed that NIS significantly reduced the population of total bacteria and fungi compared with NC(P < 0.05),while that of protazoa and methanogens were not affected(P ≥ 0.18).MON supplementation had no impact on the population of total bacteria,fungi,protozoa and methnaogens(P ≥ 0.18).In order to understand the impacts of MON and NIS on the overall rumen bacterial community,PCo A analysis was performed.A clear separation was seen among three group(P < 0.05).None of the relative abundance of bacteria at phylum level was affected by both of NIS and MON(P ≥ 0.64).At genus level,the relative abaundance of Ruminococcaceae NK4A214 group and Lachnospiraceae＿uncultured was significantly increased by NIS(P < 0.05),while the relative abundance of Muribaculaceae＿norank and Lachnospiraceae XPB1014 group was significantly increased by MON(P < 0.05).Overall,both NIS and MON addition changed rumen microbiota.The MON addition changed rumen fermentation pattern and reduced acetate/propionate ratio.In contrast,NIS addition had no effected on rumen fermentation parameters,but reduced the population of total bacteria and fungi.3.Effects of nisin on colon fermentation and microbiota in fatting Hu lambsAt the end of the experimental period,one lamb was randomly selected from each units,and slaughtered for colon contents collection.This trial was conducted to evaluate the effects of NIS subsitiuttion for antibiotics on colon fermentation and colon microbial community structure of Hu lambs.The results showed that MON significantly increased colon p H compared with negative control.Both NIS and MON reduced concentrations of total VFA and acetate(P < 0.05).The concentration of propionate was increased by MON(P < 0.05),but decreased by NIS(P < 0.05).The NIS-fed lambs had lower colon ammonia concentration than NC.Quantitative real-time PCR showed that MON significantly reduced the population of total bacteria.Both NIS and MON had no affected on the population of fungi and methanogens compared with NC.None of the alpha diversity measurements of the colon bacterial community was affected by NIS(P ≥ 0.05),MON addition significantly reduced the numbers of OTUs,Chao 1,ACE,and Shannon diversity index,but increased Simpson index(P < 0.05).In order to understand the impacts of MON and NIS on the overall rumen bacterial community,PCo A analysis was performed.MON was separated from NC and NIS(P < 0.01),while the separation was not seen between NIS and control(P ≥ 0.05).None of the relative abundance of bacteria at phylum level was affected by NIS(P ≥ 0.05).MON addition decreased the relative abundance of Firmicute,and increased the relative abundance of Bacteroidetes and Actinobacteria compared with NC(P < 0.05).None of the relative abundance of bacteria at genus level was affected by NIS(P ≥ 0.05).The MON addition had a great impact on relative abundance of colon bacteria at genus level.MON mainly decreased the relative abundance of Ruminococcaceae sp.,,and increased the relative abundance of Muribaculaceae＿norank,Lachnospiraceae NK3A20 group and Bifidobacteriaceae＿Unclassified compared with NC.Overall,Lambs receiving NIS reduced colon concentrations of total VFA and ammonia,while colon microbiota was not affected.The MON addition changed colon bacterial community structure,and decreased total VFA concentration,but increased propionate concentration.In summary,NIS addtion at 274.5 mg/kg DM and MON addition at 40 mg/kg DM had no effect on growth performance of fatting Hu lambs.NIS addition changed rumen but not colon microbial community structure,and reduced the total VFA concentration in both rumen and colon.In contrast,MON addition changed microbial community structure,and reduced acetate concentration and acetate/propionate ration in both rumen and colon.