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

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 <i>C. perfringens</i> (CCP). In a 2 × 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 (<i>p</i> < 0.05). The mRNA levels of <i>SOD</i>, <i>CAT</i>, <i>GSH-Px1</i>, and <i>GSH-Px3</i> in the liver and jejunum were upregulated by the CCP challenge (<i>p</i> < 0.05). In addition, the level of serum diamine oxidase (DAO), and the mRNA level of <i>ZO-1</i> were also upregulated with the CCP challenge. Dietary supplementation with VA contributed to the intestinal villi height and the mRNA level of <i>Mucin-2</i> in the jejunum (<i>p</i> < 0.05). Additionally, dietary VA had the ability to alleviate the upregulation of SOD in the liver and <i>SOD</i>, <i>CAT</i>, <i>GSH-Px1</i>, <i>GSH-Px3</i>, <i>ZO-1</i>, and <i>claudin-1</i> in the jejunum with the CCP challenge (<i>p</i> < 0.05). However, the mRNA level of <i>GSH-Px3</i> 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.