Background This study was conducted to evaluate the effects of dietary sodium butyrate (SB) supplementation on the antioxidant status, intestinal morphology, functional damage, and barrier integrity of heat-stressed Hy-Line Sonia (HYS) layer chicks. A total of 240 female HYS at 35 days of age with average body weights (415 ± 35 g) were divided into 6 groups with 10 replicates/group and 4 chickens per replicate. A 2 × 3 factorial design study was performed, including two conditions of ambient temperature (25 °C and 35 °C) and three dietary levels of SB (0, 0.5, and 1.0 SB g/kg diet). Results HS decreased (P < 0.05) the performance parameters final body weight (FBW), average daily gain (ADG), and average daily feed intake (ADFI), and increased mortality; compared with the HS groups, supplementation with SB decreased mortality. Compared with thermoneutral conditions, the high-temperature conditions significantly decreased (P < 0.05) the thymus, liver, and heart weights, and the relative length of the jejunum, ileum, and cecum, whereas supplementation with 0.5 SB g/kg diet increased (P < 0.05) the weight of the spleen in growing layer chickens. High temperature decreased (P < 0.05) the villus height (VH) and VH/CD ratio, and increased the crypt depth (CD), and supplementation with SB and the T × SB interaction produced greater VH and VH/CD values in the LSB2 and HSB2 groups. SB decreased (P < 0.05) the concentration of serum malondialdehyde (MDA); however, high temperature decreased (P < 0.05) the activities of the catalase (CAT) and glutathione peroxidase (GSH-Px) antioxidant enzymes. The relative mRNA expression levels of the occluding, zonula occludens-1 (ZO-1), claudin-1, and interleukin-10 (IL-10) proteins were downregulated (P < 0.05) at high-temperatures, while that of transforming growth factor-β (TGFβ) was upregulated. Dietary supplementation decreased the expression of the inflammatory cytokines nuclear factor kappa B (NF-κB), transforming growth factor-β (TGFβ), and interferon-γ (IFNγ), and the T × SB interaction decreased TGFβ gene expression in the LSB2 and HSB2 groups compared with that in the other groups of growing layer chickens. Conclusion SB supplementation effectively alleviated HS-induced oxidative stress and structural and functional damage to the intestine in layer chickens in the growing phase.
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