Effects Of Supplementary Feeding On Growth Performance,blood Index And Rumen Flora Of Grazing Calves

In order to study the effects of supplementary feeding on the growth,blood indicators and rumen flora of grazing calves.This experiment took grazing and suckling calves as the research object,and analyzed the changes in body weight,body size,blood biochemical indicators,blood amino acid levels and rumen flora abundance around the "grazing + supplementary feeding" feeding model.It aims to improve the growth and development of grazing calves and provide a theoretical basis for the breeding methods of grazing calves.Experiment 1: Sixteen days old,similar body condition and healthy grazing suckling calves were selected and randomly divided into grazing group and grazing plus supplementary feeding group.All test calves were grazing on the same pasture with the cows,and the supplementary feeding group was supplemented on the basis of grazing.From 0 to 30 days of the trial period,the daily gain of calves in the two groups was not significantly different(P>0.05),and the daily gain of calves in the grazing plus supplementary feeding group was significantly higher than that in the grazing group(P<0.05).In the whole experimental period,the body measurements of grazing and supplementary feeding group calves except for the chest circumference tended to be higher than of the grazing group(P>0.05).Experiment 2: The calf venous blood was collected early in the morning on the0 th,30th,and 60 th day of the test period to determine the relevant blood indicators.The results of supplementary feeding on blood indicators of grazing calves: urea nitrogen(BUN),glucose(GLU),insulin-like growth factor-1(IGF-1),insulin(INS),immunoglobulin G(Ig G)and interleukin-1(IL-1)indicators were significantly improved(P<0.05).And serum total protein(TP),blood ammonia(AMM),growth hormone(GH),triiodothyronine(T3),thyroxine(T4),interleukin-2(IL-2)and tumor necrosis factor ɑ The content of(TNF-ɑ)tended to be higher than that of the grazing group,but the difference was not significant(P>0.05).There was no significant difference in the activities of calf serum alkaline phosphatase(ALP),alanine aminotransferase(ALT)and aspartate aminotransferase(AST)between the two groups(P>0.05).Experiment 3: Detected 17 kinds of free amino acids in plasma.The content of essential amino acids(EAA)in the grazing plus supplementary feeding group was significantly higher than that of the grazing group(P<0.05),while the content of non-essential amino acids(NEAA)in the grazing plus supplementary feeding group was significantly lower than that of the grazing group(P <0.05).The total amino acid(TAA)content of the grazing plus supplementary feeding group tended to be higher than that of the grazing group,but the difference was not significant(P>0.05).The content of arginine,leucine and phenylalanine in blood EAA of the grazing plus supplementary feeding group was significantly lower than that of the grazing group(P<0.05),and the content of methionine,isoleucine and histidine was significantly higher than that of the grazing group(P<0.05).The NEAA content of glutamate,glycine,cystine and aspartic acid in the grazing plus supplementary feeding group was significantly higher than that of the grazing group(P<0.05),while the alanine content of the grazing plus supplementary feeding group was significantly lower than that of the grazing group(P<0.05),the content of other amino acids was not significantly different(P>0.05).Experiment 4: The coverage rate of the tested samples in this experiment reached more than 98.5%.At the end of the experiment,the Shannon index,Chao1 index and ACE index grazing plus supplementary feeding group were significantly lower than the grazing group(P<0.05).At the microbial level,the dominant bacteria in the rumen of calves are Firmicutes and Bacteroides,and at the microbial level,the dominant species in the rumen are Prevotella,RC9 flora and Rumenococcus.Branch NK4A214 group.Calf blood biochemical indicators,some growth-related hormones,enzyme activities and some immune indicators are significantly correlated with the abundance of rumen flora(P<0.05);there are 6 kinds of amino acids in EAA and NEAA that are significantly related to the abundance of rumen flora Correlation(P<0.05).