Effects Of Sodium Bicarbonate Supplementation On Rumen Fermentation,Rumen Microbiome And Epithelial Function Of Hu Sheep Fed A Pelleted Total Mixed Ration

As a new feeding strategy,the total mixed pellet diet has been widely used in ruminant production.Previous studies have shown that the total mixed pelleted diet feeding can effectively improve animal performance.However,long-term feeding of this diet would increase the risk of subacute ruminant acidosis in ruminants.As a safe strongly alkaline and lightly acid salt,sodium bicarbonate has been commonly used as a ruminal regulator for ruminants.However,its regulatory effects on the physiological functions of the rumen in Hu sheep under the total mixed pelleted diet were still unclear.Therefore,the objective of this study was to investigate the effects of supplementing sodium bicarbonate to the total mixed pelleted diet on rumen fermentation,rumen microbiome and epithelial function of Hu sheep,providing a theoretical basis for the application of sodium bicarbonate in the industry.1.Effects of sodium bicarbonate supplementation on growth performance,rumen fermentation,rumen epithelial morphology and function of Hu sheep fed a total mixed pelleted diet.The objective of this study was to explore the effects of sodium bicarbonate supplementation on growth performance,fermentation parameters,rumen epithelial morphology and function of Hu sheep fed a pelleted total mixed ration.Sixteen90-day healthy Hu sheep were selected for a 30-day experiment after a 5-day adaptation.The sheep were randomly allocated to two groups,which fed with either a basic diet(CON)or sodium bicarbonate(SB)at a dose of 5 g/kg of pelleted TMR.Feed was supplied daily in two equal portions at 0800 and 1600 h,with free access to diet and water.Daily feed intake was recorded for each animal throughout the experiment period,and it was confirmed that all feeds offered to the sheep were remain at 10 percent.The body weight was measured once a week for individual animals.At the end of the experiment,animals were slaughtered,then rumen fluid and rumen contents were collected for detection.The results showed that the average daily gain(P = 0.021)was significantly greater in the SB group than that in the CON group.The total weight gain(P = 0.067)and average daily feed intake(P = 0.062)of the SB group tended to increase compared with the CON group,while the feed conversion ratio(P = 0.074)tended to decrease.There was no significant difference in nutrient apparent digestibility(P > 0.05)between the two groups.The ruminal p H(P = 0.016)was higher in the SB group compared with CON group,while the SB group decreased the concentrations of total volatile fatty acids(P = 0.018).As compared with the CON group,the concentration of ruminal acetate(P = 0.093)in the SB group tended to decrease.The results of rumen epithelial morphology and related functional gene expressions showed that there were no significant differences between the two groups(P > 0.05).In summary,these results showed that the supplementation of sodium bicarbonate in pelleted total mixed diets improved the growth performance and rumen health of Hu sheep,while the morphology and function of rumen epithelium were not affected.2.Effects of sodium bicarbonate addition on the composition and structure of ruminal digesta-associated microbiota of Hu sheep fed a pelleted total mixed diet.The purpose of this experiment was to evaluate the effects of sodium bicarbonate addition on the composition and structure of ruminal digesta-associated microbiota of Hu sheep fed a total mixed pelleted diet.Experimental design was mentioned in chapter one.At the end of this experiment,all sheep were slaughtered after morning feeding.The rumen contents were collected for microbial DNA extraction.Then high-throughout sequencing was performed to explore the changes in the composition and structure of rumen microbiota.At the phylum level,15 phyla were recognized in the two groups through 16 S r RNA gene sequencing.Compared with the CON group,the relative abundance of Candidate＿division＿TM7(P = 0.042)was enriched in the SB group.The results revealed that there were 23 genera with relative abundance greater than 1% in the two groups.Compared with the CON group,the relative abundance of unclassified Veillonellaceae(P = 0.021)in the SB group was significantly reduced,while the relative abundance of unclassified Christensenellaceae(P = 0.043)was greatly increased.Moreover,at the OTU level,the SB group reduced the relative abundance of OTU24(Succiniclasticum,Firmicutes,P = 0.043)compared to the CON group.In general,these results suggested that the addition of sodium bicarbonate had little effect on the composition and structure of rumen digesta-associated microbiota.3.Effects of sodium bicarbonate addition on the composition and structure of rumen epithelium-associated microbiota of Hu sheep fed a pelleted total mixed dietThe objective of this study was to explore the effects of sodium bicarbonate addition on the composition and structure of rumen epithelium-associated microbiota of Hu sheep fed a pelleted total mixed diet.Experimental design was mentioned in chapter one.At the end of this experiment,all animals were slaughtered after morning feeding.The rumen epithelial tissues were collected for microbial genomic DNA extraction.Then 16 S r RNA gene sequencing was conducted to evaluate the variations in the composition and structure of epithelium-associated microbiota.At the phylum level,19 phyla were detected in the two groups through high-throughout sequencing.The dominant bacterial phylum of the two groups were Bacteroides,Firmicutes and Proteobacteria.There was no significant difference in the relative abundance of all bacteria between the two groups(P > 0.05).At the genus level,there were 41 genera with relative abundance greater than 0.05 percent in the two groups.Compared with the CON group,the relative abundance of Ruminococcaceae UCG-009(P = 0.021)and Prevotellaceae UCG-003(P = 0.043)was higher in the SB group.The relative abundance of Butyrivibrio 2(P = 0.043)was lower in the SB group than that in the CON group.Additionally,at the OTU level,the relative abundance of OTU35(Prevotellaceae UCG-001,Bacteroidetes,P = 0.029)was lower in SB group than that in the CON group.In summary,these results revealed that the addition of sodium bicarbonate had little effect on the composition and structure of rumen epithelium-associated microbiota.