Abstract: 【Objective】 The purpose of this experiment was to explore the effects of different concentrations of alfalfa polysaccharides (APS) to the diet on serum hormone indexes,antioxidant capacity,immune function,reproductive performance and fecal flora of pregnant sows.【Method】 A total of 90 pregnant sows (PIC,parity 3-4) with similar genetics,body condition,and backfat thickness,were randomly assigned to six groups using a single-factor completely randomized design.They were respectively the control group (CON) and the 200,400,600,800 and 1 000 mg/kg APS groups (experimental groups A,B,C,D and E),with 15 replicates in each group and one pig in each replicate.The trial included a 10-day pre-trial (gestation days 45-55) and an 80-day main trial (gestation day 55 to weaning).On the morning of the 55th day of the gestation before feeding,6 pigs in each group were randomly selected for blood collection through the anterior vena cava to determine serum biochemical,antioxidant capacity and immune function indicators.During the experiment,production indicators such as the total litter size of sows,total number born,and the weaning litter weight were recorded.Milk samples were collected on postpartum days 1 and 8 for the routine components analysis.The fecal conditions of sows were observed and the scores were recorded on gestation days 60,80 and 110.From gestation days 111 to 113,6 pigs were randomly selected from each group to collect fresh fecal samples and determine the diversity of fecal microbiota.【Result】 Compared with CON group,①The total antioxidant capacity in the serum of pregnant sows in groups C and D increased significantly (P＜0.5).The serum IgM content of sows in group B increased significantly (P＜0.05).②The total litter size and total number born of pregnant sows in group B,and the average weight and average daily weight gain of weaned piglets in groups C and D were significantly increased (P＜0.5).③The lactose content in the colostrum of sows in groups A,B,C,D and E increased significantly (P＜0.05).The contents of milk protein in normal milk of groups B and C,and the contents of non-fat milk solids and dry matter in normal milk of group C were significantly increased (P＜0.05).④The fecal scores of sows in each experimental group at 110 days of gestation were significantly increased (P＜0.5).⑤At the phylum level,the relative abundance of Firmicutes in fecal of sows in group A increased significantly (P＜0.05).At the genus level,the relative abundances of Escherichia-Shigella in fecal of sows in groups A and B,and Clostridium in groups A,B,C and D were significantly decreased (P＜0.05).The relative abundance of Christensenellaceae_R-7_group and Prevotella in fecal of sows in groups A and B increased significantly (P＜0.05).【Conclusion】 Under this experimental condition,dietary supplementation with 600 mg/kg APS significantly improved antioxidant capacity,immune function,and reproductive performance in gestating sows,while concurrently enhancing milk quality,alleviating constipation,and optimizing fecal microbiota diversity.

Key words: pregnant sow; alfalfa polysaccharides; reproductive performance; antioxidant capacity; fecal microbiota