Effect of vitamin E supplementation on performance and immunity of white leghorn layers during heat stress

The effect of vitamin E supplementation on performance, immune response and antioxidant status was evaluated in commercial White Leghorn (WLH) layers during heat stress (31–44°C). WLH layers (48 wk) were distributed into 5 equal groups and housed in individual California type cages in open side housing system. A basal diet (maize-soybean-sunflower-deoiled rice bran) was formulated and supplemented with vitamin E at 5, 25, 125, 250 or 500 mg/kg diet. Considering one bird as a replicate, 25 such replicates were randomly allotted to one of the five diets for 48–56 wk. The egg production increased linearly (P<0.05) by increasing the concentration of vitamin E from 5 to 125 mg/kg diet. Egg weight was not influenced due to concentrations of vitamin E in diet. However, daily feed intake increased and feed efficiency (egg mass/feed) improved significantly (P<0.05) by increasing the concentration of vitamin E from 5 to 25mg/kg diet. Increase in vitamin E levels beyond 125 mg/kg did not have additional advantage on performance. Egg quality parameters except Haugh unit were not influenced by the concentrations of vitamin E in the diet. The lipid peroxidase activity decreased while the activity of catalase and glutathione peroxidase increased by increasing the levels of vitamin E from 5 to 125 mg/kg diet. The antibody titre increased linearly (P<0.05) by supplementation of vitamin E from 5 to 125 mg/kg diet. The data from the present study suggested a higher requirement of vitamin E (125 mg/kg diet) for optimum performance, enhanced antioxidant status and better immune response in laying hens during heat stress.