Biochemical Indicators And Changes In Rumen Environment Parameters In Holstein Cows With Different Lactation Cell Counts

Ruminal microbial structure and function play an important role in regulating the health of the dairy organism,and rumen fluid interface characteristics have an important influence on the activity of rumen microbes.The aim of this experiment was to analyse the changes in biochemical indicators and parameters of the rumen environment in Holstein cows with different milk somatic cell counts,with a view to finding differences in digestive metabolism that affect mammary health in dairy cows.Firstly,Holstein cows were grouped according to the number of somatic cells in their milk,and changes in milk composition,serum biochemical parameters and relevant immune factors were measured in each group to reveal differences in the performance of cows with different numbers of somatic cells in their milk.Secondly,we measured the changes in rumen environment parameters in Holstein cows with different lactosomal cell counts,and analysed the differences in rumen fermentation capacity and rumen interface characteristics in cows with different lactosomal cell counts.Finally,the analysis of changes in rumen microbiota and rumen enzyme activity in dairy cows with different lactosomal cell counts provided a theoretical basis for further analysis of changes in the rumen environment of dairy cows with different lactosomal cell counts that regulate the physiological status of the organism.Experiment 1:Thirty one Holstein cows with similar lactation days,litter size and body weight were selected for this experiment based on the principle of similarity.Cows in the L-SCC group（14cows,<100,000 SCC/m L）,M-SCC group（8 cows,400,000～500,000 SCC/m L）and H-SCC group（9cows,>500,000 SCC/m L）were divided according to their somatic cell count,and tail-root venous blood,rumen fluid and milk were collected to determine milk composition,fatty acid composition in milk and serum parameters.The results showed that compared to cows in the L-SCC group:1)milk fat percentage in milk from cows in the M-SCC group was significantly lower（P<0.05）,and milk fat and lactose percentage in milk from cows in the H-SCC group were significantly lower（P<0.05）.2)Milk fatty acids from cows in the M-SCC and H-SCC groups,including C8:0,C10:0,C12:0,C14:0,C14:1,cis-9,C15:0,C16:0,C16:1,cis-9,C18:0,C18:1,cis-9,C18:2,cis-9,12,C21:0 were significantly decreased（P<0.05）.3)Serum levels of Ig G₂,Ig M,IL-1β,IL-6,Hpt,TNF-ɑlevels were significantly increased（P<0.05）.Trial 2:Based on the grouping of cows in Trial 1,rumen fluid was collected by mouth from each group of cows for subsequent analytical studies.The changes in the rumen environment of cows with different lactosome cell counts were investigated by measuring relevant indicators such as rumen fermentation parameters and interfacial properties in each group of cows.The results showed that compared with the L-SCC group,1)there were no significant changes in ammonia nitrogen and volatile fatty acids produced by fermentation in the rumen of cows in the M-SCC group;no significant changes in ammonia nitrogen and a significant decrease in total volatile acids produced by fermentation in the rumen of cows in the H-SCC group（P<0.05）,in which the contents of acetic acid,propionic acid,isobutyric acid,butyric acid,isovaleric acid and valeric acid decreased significantly（P<0.05）.（2）The redox potential of cows in the M-SCC and H-SCC groups increased significantly（P<0.05）,and the surface tension and cell surface hydrophobicity decreased significantly（P<0.05）.Experiment 3:16S rRNA high-throughput sequencing was applied to resolve changes in the rumen microbiota of Holstein cows with different somatic cell counts,and to further reveal changes in the rumen environment of cows with different milk somatic cell counts by measuring changes in microbial enzyme activity indicators in the rumen.The results showed that compared to cows in the L-SCC group:1)Significant increase in xylanase in the rumen of cows in the M-SCC and H-SCC groups（P<0.05）。2)coverage of rumen microbial sequencing was significantly higher（P<0.05）in cows in the M-SCC and H-SCC groups;there were no significant differences in rumen microbial species,diversity and abundance between cows in the M-SCC and H-SCC groups.3)At the phylum level,the relative abundance of Bacteroidota was significantly higher in the M-SCC and H-SCC groups,and a significant decrease in Firmicutes and Desulfobacterota（P<0.05）,while the relative abundance of other phyla did not differ significantly in the rumen of cows in the L-SCC,M-SCC and H-SCC groups.At the genus level,Prevotella dominated the rumen microflora genus,with the relative abundance of Prevotella significantly increased in cows in the M-SCC and H-SCC groups compared to cows in the L-SCC group（P<0.05）.The relative abundance of Ruminococcus,Christensenellaceae R-7 group,Rikenellaceae Rikenellaceae RC9 gut group were significantly increased（P<0.05）.In summary,the serum levels of some immunoglobulins and cytokines were significantly higher in the M-SCC and H-SCC groups compared to the L-SCC group,promoting an inflammatory response in the body.In addition,significant changes in the interfacial properties of the rumen fluid in both groups resulted in the inhibition of microbial activity and adsorption capacity,reduced feed utilisation,decreased production of various volatile fatty acids and consequent significant decreases in milk fat,milk fatty acid and lactose rates.16SrRNA assays showed that in the rumen of cows in the M-SCC and H-SCC groups,the relative abundance of bacteroidota,Prevotella.The relative abundance of these organisms was significantly increased,providing sufficient precursors for the synthesis of immunoglobulins and acute phase proteins by the inflamed organism.