Regulation Of Virginiamycin On Rumen Fermentation, Bacterial Community Structure And Its Application Of Beef Cattle

This experiment was aimed to study the effects of virginiamycin on rumen fermentation, rumen microbial community structure and growth performance, nutrient digestibility, blood biochemical parameters of beef cattle. In order to provide a theoretical basis for promoting growth mechanism of virginiamycin and and its application in ruminants.Experiment 1: This experiment was conducted to study the effects of virginiamycin on growth performance, nutrient digestibility and blood biochemical indicators of beef cattle.16 Xia Nan cattles with an initial weight of 482 kg were randomly divided into two groups.The treatment group was supplemented with 30 mg/kg virginiamycin in concentrated feed.The pre-feeding period was 5 days and the formal stage was 40 days. The results showed that:(1) The feed to weight ratio of virginiamycin group compared with the control group had significant reduction(P<0.05), the ADG of virginiamycin group was increased in a certain degree(P>0.05).(2) The virginiamycin group was compared with the control group,the digestibility of EE, NDF was increased in a certain degree(P > 0.05), the digestibility of CP and OM had a increasing trend(0.05≤P≤0.1)(3) The contents of blood IgG and blood glucose of the virginiamycin group were increased in a certain degree(P>0.05), and the contents of TP had the trend of increasing(0.05<P<0.1). The contents of blood urea nitrogen were decreased in a certain degree(P>0.05). These results indicated that virginiamycin could significantly decrease the feed to weight ratio, and have the trend of improving CP and OM digestibility and blood total protein of beef cattle.Experiment 2: This experiment was aimed to study the effects of virginiamycin on rumen fermentation and microbial protein synthesis amount of beef cattle. Using three cattles(weight in 490±20 kg)with permanent rumen fistula as experimental animals. The test used the self contrast method and was divided into control period and treatment period,the pre-feeding period was 7 days and the formal stage was 14 days. The treament period was added to 30mg/kg virginiamycin in concentrated feed, control period was not added.The results show that:(1) Virginiamycin could improve rumen pH in a certain degree(P>0.05), could significantly reduce ruminal ammonia concentration(P<0.05) and had no significant effects on concentrations of VFA(P>0.05).(2)Virginiamycin made the concentrations of urine allantoin, uric acid and urinary purine derivative increase(P>0.05).Virginiamycin made the concentrations of rumen microbial nitrogen(MN) and microbialprotein(MCP) increase by 13.30%(P>0.05). These results indicated that: Virginiamycin could improve ruminal pH in a certain degree, had no significant effect on VFA;Virginiamycin could significantly reduce concentration of NH3-N, had the function of promoting ammonia nitrogen utilization and improving the rumen MCP synthesis.Experiment 3: This experiment was aimed to study the effects of virginiamycin on rumen bacterial diversity and structure. The experiment design and animals were the same as Experiment two. We collected rumen fluid samples in day 21. Using Miseq high throughput sequencing method to determine microflora diversity and structure of rumen fluid. The results show that:(1) Virginiamycin have no significant effect on OTU number,the α diversity index(P>0.05); 577 OTUs and 556 OTUs can be respectively seen in the control group and virginiamycin group from Venn diagram, both of them contained 548 OTUs, the bacteria of two groups were similar.(2) According to the composition of bacteria phylum level. Virginiamycin made the proportion of Bacteroides increased by17.16%, Firmicutes decreased by 44.99%, Proteobacteria increased by 64.68%(P>0.05).(3) According to the composition of bacteria genus level. Virginiamycin increased proportion of Prevotella by 44.13%(P>0.05) and significantly reduced the proportion of Bifidobacteriaceae-uncultured and Streptococcus(P<0.05).(4) According to the composition of bacteria species level. Virginiamycin increased the proportion of Prevotella by 45.26%(P>0.05) and proportion of Selenomonas(P>0.05), significantly reduced the proportion of Streptococcus(P<0.05); These results suggest that: The total number and diversity of the rumen bacteria were not significantly influenced by virginiamycin, but it altered the composition of bacteria in rumen.