Abstract: The advantages of antimicrobial peptides， including broad antibacterial spectrum， immune regulation，stable biological activity，and low resistance development，are well recognized. In this study，the effect of the antimicrobial peptide product Youtide on the growth performance of Silkie chickens was evaluated，aiming to provide a scientific basis for its application in Silkie chicken production. A total of 2，889 one?day?old female Silkie chickens were selected and assigned into three groups：a production control group （Group A），a Youtide ? supplemented group（Group B），and a blank control group（Group C），with three replicates per group and 321 chickens per replicate. At 55 days of age，production performance indexes，including marketing rate，feed intake， body weight，and feed?to?gain ratio，were recorded. During the middle and late feeding stages（35 and 55 days of age），samples were collected for the observation of intestinal tissue morphology，and the levels of short-chain fatty acids as well as the load of Clostridium perfringens in the cecum were measured. In addition，cecal contents obtained from 55 ? day ? old birds were subjected to high-throughput 16S rRNA gene sequencing to analyze the microbial community structure. At 55 days of age，the average body weight and slaughter rate of Silkie chickens in the Youtide test group were found to be significantly higher than those in the blank control group （P<0.05），while the feed-to-meat ratio in the test group was observed to be significantly lower（P<0.05）. At 55 days of age，the ratio of jejunal villus height to crypt depth in the Youtide group was shown to be significantly greater than that in the blank control group（P<0.05）. At 35 days of age，the cecal contents of acetic acid，propionic acid，butyric acid，and isovaleric acid in the test group were found to be significantly elevated compared with those in the blank control group （P<0.05）. At 35 days of age，the counts of Clostridium perfringens group in the jejunum and cecum of the Youtide test group were significantly reduced relative to the blank control group（P<0.05）. No significant differences in cecal microbial community composition at the phylum or genus level were observed among the groups. Therefore，Youtide can be recommended for large?scale Silkie chicken production，as it improves intestinal morphology，inhibits harmful pathogenic bacteria，and achieves the dual benefits of promoting growth and reducing the feed?to ?meat ratio.

Key words: Silkie Chicken；Youtide；Growth performance；Clostridium perfringens group ；Short?chain fatty acids

摘要： 抗菌肽具备抗菌谱广、免疫调节、生物活性稳定以及不易产生耐药性等优势。该研究评价了抗菌肽产品—第益肽对竹丝鸡生长性能的影响，为第益肽在竹丝鸡生产中推广应用 提供科学依据。试验选取1日龄雌性竹丝鸡2 889只，分为生产对照组（A组）、第益肽组（B组） 和空白对照组（C组），每组设置3个重复，每个重复321只鸡。55日龄出栏时统计生产性能指 标，包括出栏率、采食量、体重和料肉比。饲养中期和后期（35和55日龄）分别采样，观察肠道 组织形态，测定盲肠短链脂肪酸和产气荚膜梭菌载量；55日龄的盲肠内容物另做高通量16S测 序，分析菌群结构。55日龄时第益肽试验组竹丝鸡均重、出栏率均显著高于空白对照组（P< 0.05）；第益肽试验组料肉比显著低于空白对照组（P<0.05）；55日龄时，第益肽试验组空肠绒毛 高度与隐窝深度比均分别显著高于空白对照组（P<0.05）；35日龄时，第益肽试验组盲肠内容物 乙酸、丙酸、丁酸、异戊酸显著高于空白对照组（P<0.05）；35日龄时，第益肽试验组空肠与盲肠 中产气荚膜梭菌群数量显著低于空白对照组（P<0.05）；各组的盲肠菌群门水平和属水平差异均 不显著。第益肽可改善竹丝鸡肠道形态、抑制有害致病菌、实现促生长与降低料肉比的双重效 果，可在竹丝鸡规模化生产中推广应用。

关键词: 竹丝鸡；第益肽；生长性能；产气荚膜梭菌群；短链脂肪酸