Effect Of Composite Microecologics Agents On Growth Performance,Blood Indexes And Carcass Quality Of Fattening Beef Cattle

Antibiotics can cause bacterial drug resistance and endanger human food safety,many countries have explicitly banned the addition of growth-promoting antibiotics in animal production.Microecologics is a kind of feed additive which can replace antibiotics.Microecologics,also known as live bacterial preparation,refers to the use of microecologics,the use of beneficial and harmless probiotics to the host,through a special process of living microbial preparation.Saccharomyces cerevisiae,Bacillus subtilis and Bacillus licheniformis are three common probiotics,which are widely used in the diets of calves and monogastric animals.Therefore,in this study,the above probiotics were made into a composite microecologics according to a certain proportion and added to the basic TMR diet in order to study the effects of the composite microecologics on the growth performance,serum indexes,carcass traits and meat quality of beef cattle in the later fattening stage.In order to provide a theoretical basis for the application of composite microecologics agents in beef cattle breeding and promote the production of high-quality beef products.1.Effects of dietary composite microecologics agents on growth performance of fattening cattle24 Simmental fattening beef cattle with similar body weight（408.1±15.6）kg,were randomly divided into two groups in this experiment:control group（CG）and experimental group（TG）.The pre-feeding period was 7 days,and the positive feeding period was 60days.CG group was fed with basal diet,TG group was fed with basic diet plus composite microecologics,200 g additive was added to the experimental beef cattle diet twice,and mixed well.The results showed that compared with the control group,the average daily gain（ADG）of the test group increased significantly（P<0.05）,the feed gain ratio decreased significantly（P<0.05）,the apparent digestibility of crude fat increased significantly（P<0.05）,and the apparent digestibility of（NDF）of neutral detergent fiber increased significantly（P<0.05）.There was no significant difference in apparent digestibility of（ADFI）,dry matter（DM）,acid detergent fiber（ADF）and crude protein（CP）in average daily feed intake（P>0.05）.The increase of chest circumference of fattening cattle in the experimental group was significantly higher than that in the control group（P<0.05）,but there was no significant difference in body height,oblique length,abdominal circumference,rump width,chest width and other body measurements（P>0.05）.2.Effects of dietary composite microecologics agents on blood indexes of fattening cattleThe serum growth hormone（GH）of the fattening cattle in the experimental group increased significantly from the 15th day to the 30th day of the experiment（P<0.05）.On the 45th day,the serum GH level was significantly higher than that in the control group（P<0.01）.The contents of immunoglobulin A（Ig A）,immunoglobulin M（Ig M）and immunoglobulin G（Ig G）were significantly increased（P<0.05）.There was no difference in serum biochemical indexes such as total protein（TP）,triglyceride（TG）,low density lipoprotein（LDL）,urea nitrogen（Urea）and serum thyroxine T4（P>0.05）.3.Effects of dietary composite microecologics agents on carcass traits and meat quality of fattening cattleAt the end of the feeding experiment,3 beef cattle in each group were randomly selected and slaughtered.The longissimus dorsi muscle from section 12 to section 13 of each experimental cow was selected as the experimental material for meat quality analysis.The results showed that the shearing force of beef in the experimental group decreased significantly（P<0.05）,the brightness L*increased significantly（P<0.05）,and the yellowness b*decreased significantly（P<0.05）,but there was no significant difference in pH_45min,pH_24h,drip loss and intramuscular fat between the two groups（P>0.05）.Carcass weight,slaughter percentage,eye muscle area,backfat thickness,net meat weight,bone weight,net meat weight and flesh to bone ratio;other meat quality indexes and carcass traits and carcass shape had no significant difference（P>0.05）,the average benefit of 7.75 yuan per day than the control group.In conclusion,adding composite microecologics agents（including Saccharomyces cerevisiae,Bacillus licheniformis and Bacillus subtilis）to beef cattle diet can improve the growth performance of beef cattle,enhance the body immunity and improve the quality of beef,which can bring considerable benefits to beef cattle breeding.