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This study aimed to investigate the effect of feed intake levels on the development of intestinal morphology and epithelial cell differentiation in piglets. Sixty-four 35-day-old healthy weaned piglets ([Large White × Landrace] × Duroc) with an initial weight (6.93 ± 0.12 kg) were randomly divided into four groups (100%, 80%, 40%, and 20% feed intake) with eight replicates of two pigs each. Samples were collected on days 3 and 7. The results revealed that with an increase in feed restriction degree and time, the body weight and organ index of piglets significantly decreased, and the villus height and crypt depth of the duodenum, jejunum, and ileum also decreased linearly (P < 0.05). After three days of feed restriction, jejunal ki67, endocrine cells, goblet cells, and villus endocrine/villus height all decreased linearly, but the villus cup/villus height ratio increased linearly, and the 40% and 20% were significantly higher than those of the 100% and 80% (P < 0.05). There was also a linear decrease in jejunal ki67, endocrine cells, goblet cells, and villous endocrine/villus height in piglets fed 7 days of food restriction; however, the villus goblet cells/villus height ratio in the 20% was significantly higher than that in the 40% group and was not different from that in the 80% (P < 0.05). During three days of feed restriction, the expression of jejunal differentiation marker genes showed a linear decreasing trend (P < 0.05), but increased linearly after seven days of feed restriction. The expression levels of interleukin17 (IL-17) and IL-22 also increased linearly (P < 0.05). KEGG and GSEA analyses indicated that the PPAR signaling pathway, ECM-receptor interaction, and Th1, Th2, and Th17 cell differentiation were significantly enriched in these processes. RT-QPCR demonstrated that both PPAR and ECM-receptor interactions were significantly activated during seven days of feeding restriction (P < 0.05). The results showed that with an increase in feed restriction intensity and time, the intestinal morphology and epithelial cell proliferation and differentiation were significantly reduced, except for the goblet cells. This phenomenon is related to the regulation of intestinal differentiation by IL-17 and IL-22 secreted by the Th cells., (© The Author(s) 2024. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Beta-alanine is an important amino acid involved in several metabolic reactions in the body. The study aimed to investigate the effect of β-alanine supplementation on intestinal development and the immune performance of weaned piglets. Thirty-two 21-day-old healthy weaned piglets (half female and half male; Duroc × Landrace × Yorkshire) with an initial body weight of 8.11 ± 0.21 kg were randomly divided into 4 groups with 8 replicates of 1 pig each. The control group was fed a basal diet and the three experimental treatment groups were fed diets supplemented with 300, 600 and 1,200 mg/kg β-alanine, respectively. The trial lasted 28 days and the diets fed were divided into 2 phases: the late lactation period (day 1 to 14) and the nursery period (day 15 to 28), during which the weaned piglets had free access to food and water. The regulatory effects of β-alanine were further investigated in vitro using organoids obtained from the jejunum of piglets. In vivo, the addition of β-alanine to the diet had no significant effect on the growth performance of weaned piglets ( P  > 0.05), but significantly reduced serum levels of immunoglobulin G (IgG) ( P  < 0.01), immunoglobulin M (IgM) ( P  = 0.005), and complement 3 (C3) ( P  = 0.017). The serum interleukin- 6 (IL-6) levels ( P  < 0.01) were significantly reduced in the 1,200 mg/kg treatment group. The addition of β-alanine increased ileal villus height, with the most significant effect at a concentration of 300 mg/kg ( P  = 0.041). The addition of 600 mg/kg β-alanine significantly up-regulated the expression of superoxide dismutase (SOD) activity ( P  = 0.020) and the zonula occludens-1 ( ZO-1 ) gene ( P  = 0.049) in the jejunum. Diets supplemented with 300 mg/kg β-alanine significantly increased the number of Ki67 positive cells in the jejunal crypts ( P  < 0.01). In vitro, β-alanine increased the organoid budding rates ( P  = 0.001) and the budding height of the crypt significantly ( P  = 0.004). In conclusion, β-alanine can improve intestinal morphology and barrier function, reduce inflammatory responses and alleviate the adverse effects of weaning stress on piglet intestinal health., Competing Interests: We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, and there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the content of this paper., (© 2022 The Authors. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd.)