{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,2]],"date-time":"2026-06-02T09:35:15Z","timestamp":1780392915559,"version":"3.54.1"},"reference-count":71,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2026,4,17]],"date-time":"2026-04-17T00:00:00Z","timestamp":1776384000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National Key Research and Development Program of China","award":["2023YFD1301005"],"award-info":[{"award-number":["2023YFD1301005"]}]},{"name":"Hunan Province Modern Agricultural Industry Technology System","award":["2024000127"],"award-info":[{"award-number":["2024000127"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Animals"],"abstract":"<jats:p>This study aimed to evaluate the compensatory effects of amino acid (AA) supplementation on laying hens fed a low-protein diet, focusing on production performance, egg quality, blood immunity, total tract retention, and intestinal health. A total of 180 Hy-Line Brown laying hens (35 weeks old) were randomly allocated to three dietary treatments with 12 replicates (5 hens\/replicate): (1) control diet (15.90% crude protein, CON), (2) reduced-protein diet (15.20% crude protein, NG), and (3) reduced-protein diet supplemented with 400 g\/t methionine, 400 g\/t lysine, and 300 g\/t threonine (15.20% crude protein, LAA). Over the 12-week experimental period, production parameters were monitored weekly. The results showed that compared to the NG group, AA supplementation significantly increased laying rates during weeks 1\u20134 (p &lt; 0.05) and reduced the feed-to-egg ratio during weeks 9\u201312 (p &lt; 0.05), with a 3.10% decrease in feed conversion ratio (FCR). By week 12, the NG group exhibited lower Haugh unit values than both the CON and LAA groups (p &lt; 0.05), indicating improved egg quality with AA supplementation. Serum analysis revealed elevated immunoglobulin Y levels and upregulated expression of the anti-inflammatory cytokine IL-10 in the LAA group (p &lt; 0.05). Total tract retention of crude protein (CP) and phosphorus (P) was significantly enhanced in the LAA group compared to CON and NG groups (p &lt; 0.05). However, in terms of cecal microbiota, no significant differences were observed among the experimental groups. These findings demonstrate that AA supplementation alleviates the adverse effects of low-protein diets by enhancing nutrient utilization and immune modulation, thereby improving productive performance, egg quality, and total tract retention in laying hens.<\/jats:p>","DOI":"10.3390\/ani16081232","type":"journal-article","created":{"date-parts":[[2026,4,17]],"date-time":"2026-04-17T11:53:46Z","timestamp":1776426826000},"page":"1232","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Effects of Amino Acid Supplementation in Low-Protein Diets on Productive Performance, Digestive Function, and Intestinal Health of Laying Hens"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0009-0002-8136-4393","authenticated-orcid":false,"given":"Chongyang","family":"Zhang","sequence":"first","affiliation":[{"name":"Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kangle","family":"Wu","sequence":"additional","affiliation":[{"name":"Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fang","family":"Wang","sequence":"additional","affiliation":[{"name":"Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shihang","family":"Yang","sequence":"additional","affiliation":[{"name":"Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jiayang","family":"Li","sequence":"additional","affiliation":[{"name":"Hunan Collaborative Innovation Center for Utilization of Botanical Functional Ingredients, College of Animal Science and Technology, Hunan Agricultural University, Changsha 410127, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Meizhu","family":"Xie","sequence":"additional","affiliation":[{"name":"Hunan Collaborative Innovation Center for Utilization of Botanical Functional Ingredients, College of Animal Science and Technology, Hunan Agricultural University, Changsha 410127, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yulong","family":"Yin","sequence":"additional","affiliation":[{"name":"Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kang","family":"Yao","sequence":"additional","affiliation":[{"name":"Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,4,17]]},"reference":[{"key":"ref_1","first-page":"170","article-title":"Effects of protein sources and levels in antibiotic-free diets on diarrhea, intestinal morphology, and expression of tight junctions in weaned piglets","volume":"1","author":"Wu","year":"2015","journal-title":"Anim. 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