Effects Of Compound Buffers On Growth Performance, Blood Indices And Rumen Development Of Sucking Calves

The breeding of sucking calves determines their subsequent production performance.Meanwhile,strengthening the breeding of sucking calves is an important link to improve the quality of dairy cows and create high yield and quality dairy cows.Sixty newborn calves with similar birth weight and birth time were divided into 2 groups with 30 calves per group（25 female and 5 male）.The control group was fed according to normal sucking calves in pasture,and the treatment group was fed 5 mL compound buffer（K2HPO4 10 000 mg/L,Na2HPO4 10 000 mg/L）in milk.In this study,the effects of compound buffers on growth performance and rumen development of blood index agents of sucking calves were studied,aiming to provide reference for early nutritional regulation of sucking calves.The test results are as follows:Experiment 1:To study the effects of compound buffer on the growth performance of sucking calves.Compared with the control group,there were no significant differences in feed intake,daily gain and body size indexes of calves in treatment groups after adding compound buffer（P>0.05）,but the diarrhea situation of sucking calves at 16-30 d was significantly improved.Experiment 2:To study the effects of compound buffer on blood indexes of sucking calves.Compared with the control group,the blood biochemical indices of calves in treatment group were as follows:at 1 d,the contents of GLU,TG and GLB were significantly increased（P<0.05）,and the content of BUN and NEFA were significantly decreased（P<0.05）;at 30 d,the contents of TG and BUN were significantly decreased（P<0.05）;at 45 d,the contents of GLU,IgG,NEFA and BHBA were significantly increased（P<0.05）,while the contents of TG and BUN were significantly decreased（P<0.05）;at 60 d,the contents of GLU and TG were significantly decreased（P<0.05）.Hormone and growth factor indexes of treatment groups:at 45 days,the contents of INS,IGF-1 and IGFBP-2 were significantly increased（P<0.05）;at 60 d,the contents of IGF-1 and IGFBP-2 were significantly increased（P<0.05）.Antioxidant indices of treatment group:at 1d,T-AOC content was significantly increased（P<0.05）;at 45 d,the contents of T-AOC and SOD were significantly decreased（P<0.05）.Experiment 3:To investigate the effect of composite buffers on rumen development in lactating calves.Compared with the control group,after adding compound buffer,the rumen fermentation parameters of calves in the experimental group were as follows:rumen pH was significantly increased at 30 d,45 d and 60 d（P<0.05）,and the ratio of acetic acid to propionic acid in the test group was significantly increased at 45 d（P<0.05）.Rumen microflora:there were no significant differences in microbial diversity（P>0.05）.The phylum level was shown that the relative abundance of Firmicutes was significantly decreased（P<0.05）and the relative abundance of Bacteroidetes was significantly increased at 30 d（P<0.05）.At the genus level were as follow,at 30 d,the relative abundance of Prevotella₁,Olsenella and Christensenellaceae_R-7_group in treatment group significantly increased（P<0.05）,and the relative abundance of Lachnospiraceae_NK3A20_group,Ruminococcaceae_UCG-014 and Ruminococcus₂ were significantly decreased（P<0.05）;at 45 d,the relative abundance of Christensenellaceae_R-7_group in treatment group was significantly increased（P<0.05）;at 60 d,the relative abundance of Prevotella₉ in treatment group was significantly decreased（P<0.05）,and the relative abundance of Prevotellaceae_UCG₀01 and Christensenellaceae_R-7_group were significantly increased（P<0.05）.Rumen tissue morphology:rumen papillae length,width,mucosa thickness and rumen weight had no significant differences（P>0.05）.Rumen epithelial transcription analysis:A total of 232 differentially expressed genes were screened,of which 158 genes were up-regulated and 74 genes were down-regulated.GO enrichment analysis was mainly conducted in biological processes（BP）:humoral immune response,immune response,defense response to external stimuli,and cell component（CC）:In extracellular space and extracellular region,the main pathways for KEGG enrichment analysis were:complement and coagulation cascade,drug metabolism-cytochrome P450,and tyrosine metabolism.In conclusion,the addition of complex buffers in diets has no significant effect on the growth performance of sucking calves,but can reduce diarrhea of sucking calves,improve body immunity,increase rumen pH,regulate rumen bacterial abundance,interfere with rumen environment to help maintain rumen homeostasis,and enhance rumen immune function expression,which is conducive to the early growth and development of sucking calves.