Abstract: 【Objective】 This experiment was conducted to study the effects of organic acid combined with essential oil,tannic acid and compound enzyme preparation on growth performance,serum biochemical indexes and intestinal health of weaned piglets,so as to provide theoretical basis for their production and application in piglets.【Method】 240 Duroc×Landrace×Yorkshire weaned piglets (25-day-old) with body weight of 6.48 kg±0.68 kg were randomly divided into 5 groups with 6 replicates per group and 8 piglets per replicate.The dietary treatments were as follows,basal diets (CON),CON＋5 kg/t organic acid (OA),CON＋5 kg/t OA＋800 g/t essential oil (OAEO),CON＋5 kg/t OA＋500 g/t tannic acid (OATA),and CON＋5 kg/t OA＋500 g/t compound enzyme (OACE).The pre-feeding period was 3 days and the test period was 28 days.On the first day and the 29 th day,piglets were weighed with fasting and feed intake was recorded to calculate growth performance.Feed samples and feces samples were collected to determine the apparent digestibility of nutrients.Blood samples were collected to determine serum antioxidant and immune properties.The stomach and intestinal segments (duodenum,jejunum,ileum and cecum) were separated to measured the gastrointestinal pH.Jejunal mucosa was collected to determine digestive enzyme activity.The middle part of jejunum and ileum was taken for the determination of intestinal morphology.Cecal contents were collected for the determination of short-chain fatty acids.【Result】 ①Compared with CON and OA groups,the F/G of weaned piglets in OAEO group was significantly reduced (P＜0.05).②Compared with CON group,the serum SOD activity in OA and OAEO groups was significantly increased (P＜0.05),the serum GSH-Px activity in OATA group was significantly increased (P＜0.05),the serum MDA content was significantly decreased in four treatment groups (P＜0.05).③Compared with CON and OA groups,the serum IgG,IL-2 and IL-22 levels were significantly increased in OATA group (P＜0.05),the serum D-LA levels in OAEO,OATA and OACE groups was significantly decreased (P＜0.05).④Compared with CON group,the pH of stomach,duodenum and jejunum were significantly decreased in OAEO and OACE groups (P＜0.05),and the villus height of jejunum and ileum was significantly increased in four treatment groups (P＜0.05).Compared with CON and OA groups,the activities of α-amylase,sucrase and lactase in jejunum were significantly increased in OACE group (P＜0.05),the apparent digestibility of dry matter,crude ash,ether extract and phosphorus in OATA and OACE groups were significantly increased (P＜0.05).⑤Compared with CON and OA groups,the concentration of cecal acetic acid was significantly increased in OAEO group (P＜0.05),the concentration of cecal isobutyric acid in OAEO,OATA and OACE groups was significantly decreased (P＜0.05).【Conclusion】 The combination of organic acid and essential oil had a better effect on improving the growth performance of weaned piglets, the combination of organic acid and tannic acid had a better effect on improving the antioxidant and immune performance of piglets, and the combination of organic acid and enzyme preparation has a better effect on improving the digestive function of piglets and improving the apparent digestibility of nutrients.

Key words: organic acid; essential oil; tannic acid; compound enzyme; weaned piglets; growth performance