Effects Of Diet Composition On Semen Quality Of Qinchuan Beef Bulls

The reproductive performance of bulls is affected by breed,nutrition,environment and feeding management,and one of the main factors is the difference in diet composition.Studies have shown that long-term feeding of corn silage to breeding bulls will have adverse effects on their reproductive performance.In order to explore the effect of silage in the diet on the semen quality of the new Qinchuan beef line(hereinafter referred to as Qinchuan beef cattle),and to carry out precise feeding and management of Qinchuan beef bulls,this study was carried out.In order to study the effect of diet composition on the semen quality of Qinchuan beef cattle,6 Qinchuan beef bulls of about 36 months old and healthy condition were selected as experimental animals and randomly divided into two groups with three heads in each group.The control group used 50% alfalfa hay as the main source of roughage,and the experimental group used 50% corn silage instead of alfalfa hay as the main source of roughage.By detecting various parameters of sperm,serum antioxidant indexes,sex hormone content in semen,rumen microflora and sperm transcriptome,the effect of diet composition on semen quality of Qinchuan beef bulls and how it affected semen quality were studied.The results of this test show that:1.At the end of the test,blood samples of Qinchuan beef bulls were collected to detect serum antioxidant indexes.The results showed that the test group significantly increased the serum catalase(CAT)activity of Qinchuan beef bulls(P<0.01).There were no significant differences in glutathione peroxidase(GSH-Px),superoxide dismutase(SOD)activities and malondialdehyde(MDA)content,indicating that adding silage to the diet composition helps Qinchuan cattle to decompose hydrogen peroxide in beef cattle and increases the body’s antioxidant capacity.2.Through the detection of the two groups of bovine semen parameters,it was found that the test group and the control group had no significant difference in sperm concentration,motile sperm concentration,forward motility sperm concentration and motility rate,but the bull sperm motility,forward motility and morphology normal rate in the test group were significantly different(P<0.01).It shows that adding silage to the diet composition will reduce the semen quality of Qinchuan beef bulls,which is not suitable for feeding bulls.3.The content of sex hormones in the semen of the two groups of bulls was detected.The results showed that there was no significant difference in the content of testosterone(T)and estradiol(E2)in the semen of the two groups of bulls,but the follicle-stimulating hormone(FSH)and luteinizing hormone(LH)in the semen of the test group were significantly lower than that of the control group(P<0.05),the content of inhibin B(INHB)in the semen of the test group was significantly higher than that of the control group(P<0.01),and FSH and INHB were negatively correlated.It indicated that the addition of silage to the diet composition would affect the expression of hypothalamic-pituitary-gonadal axis hormones and adversely,this will hane a negative affect on semen quality.4.The 16 Sr DNA amplicon sequencing of the test bovine rumen fluid showed that the abundance of Fibrobacterota,Bacteroidetes and Cyanobacteria in the rumen microorganisms in the test group was significantly increased(P<0.05),while the abundance of Proteobacteria was significantly decreased(P< 0.05);at the genus level,the relative abundance of Fibrobacter was significantly increased in the experimental group compared with the control group(P < 0.05),and significantly decreased the relative abundance of Acetobacter(P < 0.01).The correlation analysis between the abundance of rumen microflora and semen quality showed that the abundance of Bacteroidetes was strongly negatively correlated with sperm motility,forward motility,and morphological normal rate(P<0.05).The correlation coefficients were-0.812,-0.864,-0.836;Acetobacter abundance was strongly positively correlated with sperm motility,forward motility,and morphological normal rate(P<0.05),and the correlation coefficients were 0.947,0.940,and 0.912;The changes in the rumen microbial flora caused by the addition of silage to the diet composition will affect the semen quality of Qinchuan beef bulls.5.Transcriptome sequencing of the test bovine semen samples found that 650 differentially expressed genes were obtained between the treatment group and the control group,including 285 down-regulated genes and 365 up-regulated genes.Differential gene function prediction results showed that GO functional annotations were enriched to 39 GO items,mainly enriched in stem cell differentiation,sperm cell development,cellular calcium homeostasis,intercellular adhesion,positive regulation of responses to DNA damage stimuli,etc;KEGG pathway analysis enriched 40 signaling pathways,the pathways related to spermatogenesis include estrogen signaling pathway,signaling pathway regulating stem cell pluripotency,tumor necrosis factor signaling pathway,relaxin signaling pathway,prolactin signaling pathway,adhesive junction,glyceride metabolism and other signaling pathways.The protein interaction network constructed by the differential genes showed that there were 19 core regulatory proteins with more than 6node-connected proteins.The differential genes constituted ribosomal proteins(RPS27A,RPL23,RPS29,POLR2 F,RPL35),ubiquitin 2(UBQLN2))and acyl-Co A dehydrogenase mid-chain(ACADM)as the core regulatory network,which play a regulatory role in spermatogenesis.To sum up,it is helpful that the use of silage instead of alfalfa hay as the main source of roughage in the diet composition for the decomposition of hydrogen peroxide in Qinchuan beef bulls,affects the expression of hypothalamic-pituitary-gonadal axis hormones,and significantly reduces the Semen quality of bulls;16Sr DNA amplicon sequencing analysis of rumen fluid found that the addition of silage to the diet changed the rumen flora structure of Qinchuan beef bulls,and the change of flora structure had an adverse effect on semen quality;semen samples Transcriptome sequencing analysis showed that differential genes were involved in biological processes related to spermatogenesis,which reduced the semen quality of bulls in the experimental group.