Isolation And Identification Of Probiotics Improving The Degradation Rate Of Cellulose In Beef Cattle Feeds

Ruminants rely on cellulase secreted by rumen microorganisms to digest plant feeds that can not be used by monogastric animals.Cellulase-producing microorganisms can not only improve the feed digestibility of ruminants by pretreatment of silage in vitro,but also increase their daily gain and feed digestibility by feeding ruminants.In order to improve the utilization rate of cellulose in beef cattle roughage,the isolation and identification of cellulose degradation strains were studied in this research.Firstly,according to the standard of producing cellulase,the cellulase-producing strain was isolated from the rumen fluid of buffalo,then the strain which still had the ability of cellulose degradation in vitro was screened by corn silage test,and the safety and stress resistance of the strain were tested.finally,a microecological preparation was developed and fed to Simmental frame cattle to test its growth-promoting effect.The main contents and results are as follows:1.Isolation of strains: Using carboxymethyl cellulose degradation ability as an indicator of cellulase production,8 strains with high cellulase activity were isolated from rumen fluid of female buffalo(Nili-Lafite × Jianghan)tolerant to crude feeding.Two strains of Bacillus amyloliquefaciens(A,C),two strains of Bacillus licheniformis(E,CO4),and four strains of Bacillus pumilus(B1,B2,D1,D2)were identified.2.Cellulose degradation test in vitro: the 8 strains were tested by filter paper degradation test and corn micro silage test.All strains did not have the ability to degrade cellulose on filter paper,and 4 strains(A,C,D1,D2)could significantly reduce the contents of cellulose and hemicellulose in silage corn(silage for 90 days)(p < 0.05).Among them,compared with the blank group,strain C decreased the cellulose content by 3.10% and hemicellulose content by 1.75%,suggesting that strain C can be used as a silage fermentation enhancer to improve the utilization rate of cellulose in silage corn.Because strain C comes from buffalo,it is officially named SN-C.3.Safety test: strains A,SN-C,D1 and D2 were screened by virulence gene identification,drug sensitivity test and mouse safety test.Strain A gave up the research and development as a microecological agent after the colony was moist and the morphology of the moss growing on the cellulase detection plate was still irregular,and strain D1 and D2 contained non-hemolytic enterotoxins nhe A and nhe C,and were resistant to some veterinary penicillins and cephalosporins,so they were at risk of diffusing drug resistance,so they abandoned D1 and D2 as animal feeding microecological agents.Although SN-C contains non-hemolytic enterotoxin nhe A and nhe C,but the safety test in mice shows that it is safe,so it is selected as a subsequent microecological preparation research and development strain.4.Microbial preparation development: SN-C microbial preparations were made by SN-C microecological preparations,and SN-C and SN-6,Enterococcus HDRs Ef1 were subjected to SN-C:SN-6:Ef1=1:1:0.1 Proportional compound,made into SN-C composite microoridation formulation5.Effect of microecological preparation in beef cattle feeding experiment: a 35-day feeding experiment of Simmental frame cattle was carried out with SN-C microecological preparation and SN-C compound microecological preparation.Although SN-C alone did not increase the average daily gain of beef cattle,SN-C compound microecological preparation could significantly increase the average daily gain(1.34 kg/d in the control group and 1.44 kg/d in the compound microecological preparation group).Because the growth-promoting effect of the SN-C compound microecological preparation group was better than that of the SN-6 alone feeding group(p < 0.05 and p < 0.01 respectively),but in the compound preparation,the dosage of Enterococcus faecium HDRs Ef1 was only 5%,suggesting that SN-C has a growth-promoting effect in the compound microecological preparation.This research shows that the SN-C strain can significantly reduce the cellulose content in silage corn,and the hemicellulose content also has a decreasing trend,which proves that it has the potential as an additive to silage.In addition,the feeding test of beef shelf cattle suggests that SN-C has the potential as a growth-promoting microecological agent for beef cattle.