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.