The Effect Of SARA On Rumen Function And Production Performance Of Holstein Steers In The Late Fattening Period

Subacute rumen acidosis（SARA）is a major disease that is unhealthy breeding of beef cattle.Reducing the risk of SARA has certain significance in maintaining normal rumen function and improving productivity in beef cattle.The purpose of this experiment is to reduce the incidence of SARA of Holstein steers in the late fattening period through nutritional regulation,so as to produce high-quality beef and improve breeding efficiency.Fifteen Holstein steers of late fattening period（18 months of age）were selected from an beef cattle farm,and randomLy divided into three groups:SARA group group,test group 1 and test group 2,five heads per group.Test period is 120 days,Weighed and calculated the average feed intake,average daily gain,and feed-to-weight ratio at the 30 d,60 d,90 d,and 120 d during the test period;The concentrations of rumen lactic acid（LA）,Short-chain fatty acids（SCFA）,lipopolysaccharides（LPS）and the rumen fluid pH were detected;The concentrations of serum hydrion（H⁺）,bicarbonate ions（HCO₃^-）,triglycerides（TG）,urea nitrogen（BUN）,total protein（TP）,albumin（ALB）,globulin（GLO）and the activity of serum alanine aminotransferase（ALT）,aspartata aminotransferase（AST）,alkaline phosphatase（ALP）were detected;Rumen epithelial tissue samples were taken for immunohistochemical analysis,and score for laminitis at the end of the test period（120 d）.The results are as follows:（1）In terms of the incidence of SARA and clinical examination:With the extension of the test period,the rumen fluid pH value of Holstein steers in each group was significantly decreased（P<0.01）,and the SARA group was extremely lower than test group 2（P<0.01）and 1（P<0.05）on the 120th day,while the incidence of SARA in the test group 2（40%）was lower than the SARA group（100%）and test group 1（60%）;The SARA group and test group 1 Holstein steers’s ruminant frequency was extremely reduced before and after the test period（P<0.01）,which was significantly at the test group 2（P<0.05）,and the test group 2 was extremely higher than SARA group on the 90th day（P<0.01）,the test group 2 was higher than the SARA group and test group 1 on the 120th day（P<0.01）;The SARA group group’s laminitis score reached M4,which was higher than the test group 1（M3）and 2（M2）.（2）In terms of rumen fermentation metabolism and epithelial damage:With the extension of the test period,with the increase of the concentrations of LA,SCFA,and LPS in rumen fluid of Holstein steers in each groups,the concentrations of LA and LPS in the test group 2 were always extremely lower than SARA group（P<0.01）,the concentrations of SCFA in the test group 2 was extremely higher than SARA group group on the60th and 90th days,（P<0.01）.On the end of the test period,a larger number of inflammatory cell was infiltrated in the propria of Holstein steers ruminal mucosa in the SARA group;The rumen epithelial local tissue in the test group 1 was excessively keratinized,and a small number of lymphocyte was infiltrated in the propria of the mucosa;The keratinized layer was obvious,but no apparent gross lesions.（3）In terms of blood index:The concentrations of blood H⁺and HCO₃^-of Holstein steers in each group were significantly before and after the test period（P<0.01）;On the 60th and 120th days,the the concentrations of H⁺in the test group 2 was lower than SARA group（P<0.05）;The concentrations of HCO₃^-in the test group2 was always higher than the SARA group（P<0.01）and test group 1（P<0.05）.The activity of ALT in the SARA group was significantly increased with the extension of the test period（P<0.01）,while the activity of AST was significantly increased（P<0.05）;On the 90th day,the activities of ALT and AST in the test group 2were lower than that in SARA group（P<0.05）;On the 120th day,the activity of AST in the test group 2 was extremely lower than that in SARA group and test group 1（P<0.01）.The concentrations of TG in each group was significantly inceased before and after the test period（P<0.01）;On the 120th day,the concentrations of TG in the test group 2 was lower than that in SARA group（P<0.05）.With the extension of the test period,the concentrations of TP in the SARA group was significantly decreased（P<0.05）,the concentrations of GLO in the SARA group was decreased（P<0.01）,while the ALB-to-GLO ratio was increased（P<0.05）.（4）In terms of growth performence and breeding benefits:The feed-to-weight ratio of Holstein steers in each group was extremely decreased in the test（P<0.01）;The daily net profits of the three groups increased in turn,which respectively were 2.06,2.26,and 2.95 yuan per head.According to the results of the experiment,when the the Holstein steers has SARA,the rumen epithelial local tissue integrity and function were impaired due to abnormally increased levels of LA,CFA and LPS,and the prevalence is deepened with the extension of the fattening period and the increase of concentrate-to-forage ratio;In the late fattening period of Holstein steers,the test group 2 feeding method（concentrate-to-forage ratio 6.7:3.3,Nemf 8.45 MJ/kg）can effectively reduce the incidence of SARA,and achieve Holstein steers fattening quality efficiency.