Abstract: 【Objective】 The aim of the study was to investigate the effects of dietary vitamin D (VD) supplementation on reproductive performance of sows,growth performance of piglets and fecal flora of sows and piglets.【Method】 Forty pregnant sows (7±1 fetal periods,Yorkshire×Landrace) were selected and randomly divided into 2 groups with 20 replicates per group and 1 sow per replicate.The sows in control group were fed the basal diet,and each sow in VD group was supplemented with 1.0 g/d VD on the basis of the basal diet.The trial lasted from day 90 to day 113 of gestation and from the begainning to day 14 of lactation.The reproductive performance of sows (labor course,litter size,born alive rate,mummy rate,etc.) and the growth performance of piglets (birth litter weight,weaning litter weight,diarrhea rate,etc.) were measured during the experiment.Fecal samples of sows at day 113 of gestation, 14 of lactation, and piglets on 14 days old were collected for high-throughput sequencing of 16S rRNA gene,and microbial community structure and diversity were analyzed.【Result】 Compared with the control group,the mummy rate and IUGR rate of pregnant sows in VD group were significantly decreased (P＜0.05),and the average litter weight of newborn piglets was significantly increased (P＜0.05).Shannon index of lactating sows in VD group was significantly increased (P＜0.05).At phylum level,compared with control group,the abundance of Proteobacteria and Firmicutes in feces of pregnant sows in VD group was significantly decreased (P＜0.05).The abundance of Spirochaeta in fecal microorganisms of lactating sows was significantly increased (P＜0.05).The abundance of Bacteroidetes was significantly increased in lactating piglets,while the abundance of Spirochaeta and Firmicutes and the ratio of Firmicutes to Bacteroidetes were significantly decreased (P＜0.05).At genus level,compared with control group,the abundance of Family_ⅩⅢ_AD3011_group in fecal microorganisms of pregnant sows in VD group was significantly decreased,and the abundance of Candidatus-saccharimonas was significantly increased (P＜0.05).The abundances of Treponema and Parabacteroides in fecal microorganisms of lactating sows were significantly increased (P＜0.05).【Conclusion】 Supplementation of VD during late gestation and lactation period could improve the reproductive performance of sows,increase the relative abundance of beneficial bacteria such as Firmicutes,Bacteroides,Spirochaeta,Treponema and Paracellosis in fecal flora of sows and piglets,and reduce the relative abundance of harmful bacteria such as Proteobacteria,thereby improving the intestinal microbial structure of sows and piglets and achieving a new balance of intestinal microbes.

Key words: vitamin D; reproductive performance of sows; growth performance of piglets; fecal flora