Effects of Dietary Supplementation with Vitamin A on Antioxidant and Intestinal Barrier Function of Broilers Co-Infected with Coccidia and Clostridium perfringens

Coccidia and C. perfringens are the main accomplices in broiler necrotizing enteritis (NE), and NE causes oxidative stress and intestinal damage in broilers, which will result in huge economic losses to the poultry industry. Vitamin A (VA) is an essential micronutrient of the diet, and the beneficial effects of VA on vision, growth, and development have been intensively investigated. At present, the effects of VA on intestinal barrier and antioxidant functions in broilers have not been systematically reported. The present study was conducted to investigate the effects of dietary supplementation with vitamin A on the antioxidant and intestinal barrier function of broilers co-infected with coccidia and C. perfringens (CCP). Our outcomes showed that dietary VA might help a little with intestinal barrier function; nonetheless, it failed to alleviate the negative effects of CCP on the antioxidant function in broilers. Our study has guiding significance for the dose of VA in the diet of broilers, and it might arouse readers' strong interest. Necrotic enteritis (NE) impairs poultry production and causes great economic loss. The nutritional regulation of diets has the potential to alleviate NE. The present study was conducted to investigate the effects of dietary supplementation with vitamin A (VA) on the antioxidant and intestinal barrier function of broilers co-infected with coccidia and C. perfringens (CCP). In a 2 x 2 factorial arrangement, 336 one-day-old Ross 308 broilers were divided into four treatments with two levels of VA (0 or 12,000 IU/kg) and challenged with or without CCP. The animal trial lasted for 42 days. The results showed that dietary supplemental VA improved body weight gain (BWG) and the feed intake (FI), and the FI was negatively affected by CCP. Additionally, the levels of catalase (CAT) in the serum, total superoxide dismutase (T-SOD), and CAT in the jejunum and glutathione peroxidase (GSH-Px) in the liver decreased with the CCP challenge (p < 0.05). The mRNA levels of SOD, CAT, GSH-Px1, and GSH-Px3 in the liver and jejunum were upregulated by the CCP challenge (p < 0.05). In addition, the level of serum diamine oxidase (DAO), and the mRNA level of ZO-1 were also upregulated with the CCP challenge. Dietary supplementation with VA contributed to the intestinal villi height and the mRNA level of Mucin-2 in the jejunum (p < 0.05). Additionally, dietary VA had the ability to alleviate the upregulation of SOD in the liver and SOD, CAT, GSH-Px1, GSH-Px3, ZO-1, and claudin-1 in the jejunum with the CCP challenge (p < 0.05). However, the mRNA level of GSH-Px3 and the levels of SOD in the liver and jejunum were downregulated with the VA supplementation in the diet. In conclusion, dietary VA improved the growth performance and the intestinal barrier function; nonetheless, it failed to alleviate the negative effects of CCP on the antioxidant function in broilers.