Effects of feeding diets supplemented with vitamin E and vitamin C on performance, egg quality and stereological and structural analysis of the liver of laying hens exposed to heat stress.

This study was conducted to determine the effects of vitamin E and vitamin C on performance, egg quality and histopathological effect on the liver tissue of laying hens exposed to heat stress. A total of 256 lohman LSL laying hens were randomly assigned to 16 treatment groups, four replicates of 4 birds each. The birds with a 2×2×4 factorial design kept at normal (20°C) or heat stress (30°C) and either received either two levels of vitamin C (0 and 100 mg/L of drinking water) or four levels of vitamin E (0, 45, 65 or 85 U/kg of diet) for 11 weeks, in which one week was allowed for an acclimation period. Heat stress caused significant (P<0.05) decrement in the average feed intake, egg yields, egg shell thickness and Haugh unit. Supplementation of vitamin E increased significantly (P<0.01) the feed efficiency, egg yield and Haugh unit. The heat stress condition caused an increases in density of necrotic cell, but the area of parenchyma significantly decreased by heat stress in liver. Addition of 45 and 65 U vitamin E/kg to feeds significantly decreased density of necrotic cells. In coclusion, although supplementation of 85 U vitamin E increased feed conversion, Haugh unit and egg production, resulting in the highest degree of liver damage. Therefore, we thought that a supplementation of 65 IU of vitamin E/kg in diets appeared to be the most efficacious dose. [ABSTRACT FROM AUTHOR]