Dietary vitamin A supplementation improves intestinal morphology and immune performance of goslings

. A 28-day experiment was conducted to evaluate the effects of dietary vitamin A (VA) levels on intestinal morphology and immune performance of goslings. Healthy, one-day-old goslings (360) of similar body weight were randomly divided into six groups fed diets supplemented with 0 (A), 3 000 (B), 6 000 (C), 9 000 (D), 12 000 (E), and 15 000 (F) IU/kg VA. Compared to group A, villus height in group D, as well as villus width and crypt depth in groups C and D were increased in the duodenum (quadratic effect, P < 0.05); villus height and villus width in groups B, C, D and E, and crypt depth in groups C and D were increased in the jejunum (quadratic effect, P < 0.05); villus height and villus width in groups C and D, and crypt depth in groups B, C, D, E and F, as well as muscular layer thickness in group D were increased in the ileum (quadratic effect, P < 0.05). Serum immunoglobulin A in groups B, C, D and E, and serum immunoglobulin G levels in groups D and E were higher than in group A (quadratic effect, P < 0.05). Serum interleukin-1 (quadratic effect, P < 0.05) and interleukin-6 (linear and quadratic effect, P < 0.05) levels in groups D and E, and serum interleukin-2 level (quadratic effect, P < 0.05) in group C were higher compared to group A. In conclusion, dietary supplementation with 6 000–9 000 IU/kg VA improved intestinal morphology and immune performance of goslings.