Effect Of Different Dirtary Biological Agents On Growth Performance,Nutrient Digestion And Ruminal Microbial Flora Of Dorper×thin-tailed Han Crossbred Mutton Lambs

The aim of this study was to provide a theoretical basis for the substitution of probiotics for antibiotics and their development direction.Chose Monensin,Bacillus licheniformis,Saccharomyces cerevisiae or Compound biological agent as additives.Experimental animals are Dorper×thin-tailed Han crossbred lambs,carried out feeding experiment,digestion and metabolism experiment and slaughter test.To investigate effect of different biological agents in diets on growth performance,nutrient digestion and Utilization,ruminal microbial flora of Dorper×thin-tailed Han Crossbred mutton lambs.Experiment 1 Effects of Dietary Supplementation of Different Biological Agents on Growth and Slaughter Performance of Dorper×Thin-Tailed Han Crossbred Mutton Lambs.This experiment was conducted to study the effects of dietary supplementation of different biological agents on growth performance,Slaughter performance,tissue and organ development and meat quality of Dorper×thin-tailed Han crossbred mutton lambs.One hundred and sixty Dorper×thin-tailed Han crossbred F₁mutton lambs（weighted about 32 kg）were randomly assigned into 5 groups with 4 replicates in each group and 8 mutton lambs per replicate according to a single factor experimental design.Control group used a basal diet,21 mg/kg monensin,4×10⁹CFU/kg Bacillus licheniformis,3.2×10⁹CFU/kg Saccharomyces cerevisiae and 1.1 g/kg compound biological agents（Bacillus licheniformis,Saccharomyces cerevisiae and alkaline proteinase）were supplemented in experimental groups.The pretest lasted for 10 d,and the test lasted for 56 d.Feed intake was recorded every 2 d and lambs were weighed every 20 d.Ten lambs from each group were slaughtered to determine slaughter performance,tissue and organ weight and meat quality after body weight of lambs in compound biological agents group reached 50kg.The results showed as follows:1)for average daily gain and dressing percentage,compound preparation group was significantly higher than control group（P<0.05）;feed to gain ratio in B.licheniformis group and compound preparation group was significantly lower than that in control group（P<0.05）.2)Complex stomach weight in B.licheniformis group,S.cerevisiae group and compound preparation group was significantly higher than that in control group（P<0.05）,and the percentage of complex stomach weight of live weight before slaughter（LWBS）in compound preparation group was significantly higher than that in control group and monensin group（P<0.05）;small intestine weight and its percentage of LWBS in B.licheniformis group,S.cerevisiae group and compound preparation group were significantly higher than those in control group and monensin group（P<0.05）.3)The percentage of kidney weight of LWBS in S.cerevisiae group was significantly higher than that in control group,while the other internal organ weight percentages of LWBS were not significantly different among groups（P>0.05）.4)Meat quality indexes had no significant difference among groups（P>0.05）.In conclusion,from the effects as feed additives on growth performance of mutton lambs,Bacillus licheniformis,Saccharomyces cerevisiae and compound biological agents can replace monensin,and Bacillus licheniformis is better than Saccharomyces cerevisiae,and compound biological agents has the best effect.Experiment 2 Effects of different biological agents in diets on nutrient digestion and utilization of Dorper×thin-tailed Han Crossbred mutton lambs.Four lambs in each group were selected for a digestibility trial after the lambs in compound preparation group reached 37 kg of BW.The digestibility trial lasted for 13 days including 7 days of adaptation period.The results showed as follows:apparent digestibility of dry matter and acid detergent fiber in biological agents group was significantly higher than that in control group（P<0.05）,apparent digestibility of dry matter in compound preparation group was higher than that in monensin group and B.licheniformis group（P<0.05）,apparent digestibility of organic matter in compound preparation group had the same trend as apparent digestibility of dry matter,and was significantly higher than that in control group,monensin group（P<0.05）;apparent digestibility of gross energy,metabolizability of gross energy in biological agents groups were significantly higher than those in control group（P<0.05）;apparent digestibility of nitrogen in biological agents groups were significantly higher than that in control group（P<0.05）.The apparent digestible nitrogen and apparent digestibility of nitrogen in compound preparation group were significantly higher than those in control group,monensin group and B.licheniformis group（P<0.05）.In terms of nutrient digestion and utilization and energy and nitrogen metabolism,Bacillus licheniformis,Saccharomyces cerevisiae and compound preparations of protease and probiotics were better than monensin,and compound preparations of protease and probiotics has the best effect.Experiment 3 Effects of different biological agents in diets on serum parameters and ruminal microbial flora of Dorper×thin-tailed Han Crossbred mutton lambsTen lambs from each group were slaughtered to determine rumen fermentation parameters and ruminal microbial flora after body weight of lambs in compound biological agents group reached 50 kg.Blood samples were drawn from the jugular vein by vein puncture into vacutainer tubes in the morning,then determine serum parameters.The results showed as follows:1)for concentrations of IgA,IgG and IgM in the serum,B.licheniformis group and compound biological agents group were significantly higher than control group（P<0.05）;concentrations of IgA,IgG in S.cerevisiae group was significantly higher than that in control group（P<0.05）.The serum concentrations of SOD and GSH-PX of the compound biological agents group was significantly higher than those in control group（P<0.05）.Compared with the control group,the serum concentration of GH and INS were higher for lambs in B.licheniformis group（P<0.05）,the serum concentration of GH and IGF-I were higher for lambs in S.cerevisiae group（P<0.05）,the serum concentration of GH,IGF-I and INS were higher for lambs in compound biological agents group（P<0.05）.2)There were lower concentrations of NH₃-N for lambs in when the lambs were fed Monensin,Bacillus licheniformis,Saccharomyces cerevisiae or Compound biological agent compared with the control diet（P<0.05）;concentrations of MCP of B.licheniformis group and compound biological agents group were significantly higher than control group（P<0.05）.The lambs fed one of the Monensin,Bacillus licheniformis,Saccharomyces cerevisiae or Compound biological agent had higher concentrations of propionate and butyrate than those in the control group（P<0.05）.And had lower concentrations of acetate and acetate:propionate ratios than those in the control group（P<0.05）.3)The Lachnoclostridium＿10 from the B.licheniformis group was more abundant compared with the control group（P<0.05）.The lambs supplemented with Saccharomyces cerevisiae tended to increased the proportion of Fibrobacter（P<0.05）in total reads.In the compound biological agents group,the Alloprevotella had the highest relative abundance（P<0.05）.In conclusion,Bacillus licheniformis,Saccharomyces cerevisiae and Compound biological agents could improve serum immunity,improve rumen fermentation,and regulate the rumen microflora of lambs.Comprehensive studies had show that the addition of Bacillus licheniformis,Saccharomyces cerevisiae and compound biological agents to the diet of Dorper×thin-tailed Han crossbred lambs producesd a beneficial effect on nutrient digestibility and utilization,serum traits,and ruminal fermentation of mutton sheep,and it also had effects on rumen microbes,improved the growth performance and slaughter performance of mutton lambs.