Effects Of Dietary Fiber On Reproductive Performance And Intestinal Microbiota During Pregnancy

Dietary fiber is often supplemented in sow gestation diets.The effect of dietary fiber supplementation during gestation on sow reproductive performance were inconclusive and the mechanisms remain unclear.Gut microbiota is in close connection with nutrition,metabolism,reproduction and health of the host.Fiber can regulate intestinal microbiota composition and is fermented by microorganisms into SCFA as energy source and signaling molecules for the host.Two experiments were designed in this study to explore the effect of fiber treatment during gestation on reproduction and the role of intestinal microorganisms and its fermentation product SCFA.Trail 1: A total of 190 sows were selected and random Ly allocated in six treatment groups according to parity and backfat thickness,with TDF level as the trail factor.Sows were fed the experimental diet throughout gestation with different TDF levels（CON: 12.5% TDF;T1: 17.4% TDF;T2: 17.7% TDF;T3:18.1% TDF;T4: 18.4% TDF;T5: 18.8% TDF）.All the groups received isocaloric diets on a DE basis.Sow serum and feces were collected on the d30,d60,d90 and d110 of pregnancy.The serum of neonatal and weaning piglets was collected.The serum biochemical parameters of the sows and piglets,the short-chain fatty acid content of the sow feces and the microbial composition were detected.Litter performance and lactation performance were measured and recorded during the trail.The results are as follows:（1）Reproductive performance: Sows fed T5 diet had more piglets born alive than sows fed CON,and had a tendancy to increase the number of total born.Regression analysis suggested that dietary fiber level positively affected the total piglets born and piglets born alive.（2）Serum biochemical parameters: T3-T5 treatment reduced serum glucose levels in sows.T1-T5 treatment reduced the blood glucose and FFA level of newborn piglets,and had a tendency to increase the blood glucose level of weaning piglets.T1-T4 treatment reduced FFA level of weaning piglets.（3）Fecal SCFA: T5 treatment increased the fecal butyrate and tended to increase acetate and total short-chain fatty acid.（4）Fecal microbiota: Different fiber level did not affect the fecal microbial alpha diversity,but changed the beta diversity on d60 and d110 of pregnancy.The results analyzed on phylum and genus levels are as follows:a)At the phylum level,the relative abundance of Proteobacteria and Acidobacteria in the T4 treatment group was the highest,which was significantly higher than that in the control group（P < 0.05）.Correlation analysis showed that the abundances of Tenericutes and Actinobacteria were negatively correlated with TDF levels,while Fibrobacteres were positively correlated with TDF levels（P < 0.05）.b)At the genus level,different dietary TDF levels significantly changed relative abundance of seven genus.Streptococcus in Firmicutes,Prevotellaceae_NK3B31_group,Prevotella₁ and Prevotella₉ in Bacteroides,and Succinivibrio in Proteobacteria were negatively correlated with TDF levels,while Prevotellaceae_UCG-001 was positively correlated with dietary TDF levels（P < 0.05）.The abundance of Prevotellaceae_NK3B31_group decreased with dietary fiber addition,and the control group was significantly higher than the T1,T2 and T4 groups（P < 0.05）.In addition,Phascolarctobacterium abundance was highest in T2 group,Lachnospiraceae_XPB1014_group and Oscillospira abundance were highest in T3 group,and Turicibacter abundance was highest in T4 group（P < 0.05）.Trail 2: A total of 128 female C57BL/6J mice with similar body weight were selected and random Ly distributed into 4 groups.Mice were fed the experimental diet throughout pregency.mice were fed fiber-free diet（NF,0% fiber）,high fiber diet（HF,10% fiber）,fiber-free diet + probiotic（PRO）and sodium butyrate diet（Na Bu,fiber-free diet + 5% sodium butyrate）.The maternal body weight and feed consumption during pregnancy and lactation were weighted weekly.Litter performance,and lactation performance were measured and recorded during the trail.Maternal feces were collected at d14.5 of gestation to detect short-chain fatty acid and intestinal microbial composition.Eight female mice were sacrificed per treatment at d17.5 of pregnancy to examine fetal growth performance.The results are as follows:（1）Reproductive performance: Dietary treatments have no effect on fetal growth performance.HF group significantly increased the birth weight of the pups,as well as the average daily feed intake during gestation and the first week of lactation.（2）Serum biochemical parameters: The levels of total cholesterol and HDL-C in NaBu treatment showed a significant increase when compared with NF group;the level of LDL-C in HF group had the highest value among the four groups（P < 0.05）.（3）Placental gene expression: Diet treatments had no significant effect on placental tissue structure,but significantly affected the expression levels of Igf1,Slc38a4 and Vegfa genes.HF group and Na Bu group had a increased expression of Igf1 and Slc38a4（P < 0.05）,and PRO group decreased the expression of Vegfa（P < 0.05）.（4）Fecal SCFA: HF group showed a significant higher level of fecal acetic acid,propionic acid and total SCFA among other groups（P < 0.05）.HF group had elevated valeric acid leval compared with PRO group and Na Bu group（P < 0.05）.Na Bu group had lower butyric acid levl compared with NF group（P < 0.05）.（5）Fecal microbes: Different treatments did not affect fecal microbial alpha diversity during pregnancy,but β diversity in HF group was significantly different from other groups.The analysis results of microbial phylum and genus are as follows:a)At the phylum level,dietary treatments had no significant effect on the abundance of each phylum.b)At the genus level,dietary treatments during pregnancy significantly changed the relative abundance of six genera（P < 0.05）.The abundance of Faecalibaculum in the Na Bu group was significantly higher than that in the HF group and the PRO group（P < 0.05）.The abundances of Parabacteroides,Helicobacter and Butyricimonas in the PRO group were significantly higher than those in the other groups,while the abundances of Muribaculum and Odoribacter in the HF group were significantly higher than those in the other groups（P < 0.05）.The heat map at genus level showed that the HF group has higher content of SCFA-producing bacteria Alloprevotella,Akkermansla and Alistipes and beneficial bacteria Turicis and Odoribacter.That indicates that the HF group can modify gut microbial composition with a higher abundance of SCFA-producing bacteria and beneficial bacteria.In summary,the results of this study indicate that the number of piglets total born and born alive are linearly increased with dietary TDF level,18.8% TDF treatment has the optimal reproductive performance.However,different dietary TDF levels have limited effects on gut microbiota but increased butyrate fermentation during pregnancy.Further studies have revealed that 10% fiber level can increase maternal feed intake and birth weight of the pups,and improve the intestinal microflora and SCFA fermentation of during pregnancy,while sodium butyric acid and probiotics have no such effects.It is suggested that intestinal microbial fermentation has a certain contribution to the improvement of reproductive performance.