{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,17]],"date-time":"2026-06-17T14:30:56Z","timestamp":1781706656781,"version":"3.54.5"},"reference-count":42,"publisher":"MDPI AG","issue":"17","license":[{"start":{"date-parts":[[2025,9,2]],"date-time":"2025-09-02T00:00:00Z","timestamp":1756771200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100012166","name":"National Key Research and Development Program of China","doi-asserted-by":"publisher","award":["2022YFD1300702"],"award-info":[{"award-number":["2022YFD1300702"]}],"id":[{"id":"10.13039\/501100012166","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Animals"],"abstract":"<jats:p>Glutamine (Gln) supplementation during the weaning period can alleviate stress in piglets. However, free Gln has poor stability and low absorption in the small intestine. Glycyl-glutamine (Gly-Gln), a stable dipeptide form of Gln, has been evaluated as a potential alternative in pig nutrition. This study investigated the effects of Gly-Gln at 0, 0.125%, 0.25%, 0.375%, and 0.50%, as well as a Gly + Gln positive control, on growth performance, intestinal morphology, immunity, antioxidant status, and nutrient apparent digestibility in weaned piglets. The results showed that dietary supplementation with 0.25%, 0.375%, or 0.50% Gly-Gln significantly increased average daily gain, average daily feed intake, and final weight (p &lt; 0.05). Linear and quadratic effects (p &lt; 0.05) were observed for growth performance indicators, suggesting that moderate supplementation levels yielded optimal benefits. Dietary Gly-Gln supplementation with 0.25%, 0.375%, or 0.50% Gly-Gln significantly increased serum immunoglobulin (IgG, IgA, and IgM), insulin, insulin growth factor 1, growth hormone, and T4 and T3 contents, and decreased IFN-\u03b3 and IL-1\u03b2 contents (p &lt; 0.05). Diets supplemented with 0.25, 0.375, or 0.50% Gly-Gln increased total antioxidant capacity and superoxide dismutase content in serum and liver, and decreased MDA content (p &lt; 0.05). Compared with the negative control group, dietary supplementation of 0.25%, 0.375%, or 0.50% Gly-Gln significantly increased the mRNA expression of ZO-1, Occludin, and Claudin-1 in the jejunum (p &lt; 0.05). Furthermore, crude protein digestibility was significantly improved in piglets receiving 0.375% and 0.5% Gly-Gln (p &lt; 0.05), with a significant linear relationship between Gly-Gln level and digestibility. In conclusion, 0.25% is the minimum effective dose of Gly-Gln for improving weaning outcomes. Gly-Gln is more effective than equivalent doses of free glycine and glutamine in enhancing growth performance, gut barrier integrity, and nutrient utilization in weaned piglets.<\/jats:p>","DOI":"10.3390\/ani15172573","type":"journal-article","created":{"date-parts":[[2025,9,2]],"date-time":"2025-09-02T09:24:41Z","timestamp":1756805081000},"page":"2573","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Dietary Glycyl-Glutamine Supplementation Improves Growth, Immunity, Antioxidant Capacity, and Apparent Digestibility of Weaned Piglets"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0009-0005-0272-2730","authenticated-orcid":false,"given":"Xi","family":"Jiang","sequence":"first","affiliation":[{"name":"School of Materials and Chemical Engineering, Hubei University of Technology, Wuhan 430068, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1246-1926","authenticated-orcid":false,"given":"Dong","family":"Li","sequence":"additional","affiliation":[{"name":"School of Materials and Chemical Engineering, Hubei University of Technology, Wuhan 430068, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mengli","family":"Chen","sequence":"additional","affiliation":[{"name":"Hunan Provincial Key Laboratory of Animal Nutritional Physiology and Metabolic Process, National Engineering Laboratory for Pollution Control and Waste Utilization in Livestock and Poultry Production, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China"},{"name":"Laboratory of Animal Nutrition and Human Health, College of Life Sciences, Hunan Normal University, Changsha 410013, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jianzhong","family":"Li","sequence":"additional","affiliation":[{"name":"Laboratory of Animal Nutrition and Human Health, College of Life Sciences, Hunan Normal University, Changsha 410013, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0007-3504","authenticated-orcid":false,"given":"Xihong","family":"Zhou","sequence":"additional","affiliation":[{"name":"Hunan Provincial Key Laboratory of Animal Nutritional Physiology and Metabolic Process, National Engineering Laboratory for Pollution Control and Waste Utilization in Livestock and Poultry Production, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China"},{"name":"College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing 100049, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6750-5888","authenticated-orcid":false,"given":"Xia","family":"Xiong","sequence":"additional","affiliation":[{"name":"Hunan Provincial Key Laboratory of Animal Nutritional Physiology and Metabolic Process, National Engineering Laboratory for Pollution Control and Waste Utilization in Livestock and Poultry Production, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China"},{"name":"College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing 100049, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0248-6900","authenticated-orcid":false,"given":"Yulong","family":"Yin","sequence":"additional","affiliation":[{"name":"Hunan Provincial Key Laboratory of Animal Nutritional Physiology and Metabolic Process, National Engineering Laboratory for Pollution Control and Waste Utilization in Livestock and Poultry Production, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China"},{"name":"College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing 100049, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,9,2]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"3634","DOI":"10.2527\/jas.2010-3751","article-title":"Intestinal growth and morphology is associated with the increase in heat shock protein 70 expression in weaning piglets through supplementation with glutamine","volume":"89","author":"Zhong","year":"2011","journal-title":"J. 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