The effect of natural and synthetic antioxidant on performance, egg quality and blood constituents of laying hens grown under high ambient temperature

A total 216 laying hens was kept at high ambient temperature (32 +/- 4 degrees C, 60% relative humidity) from week 24 to 32 of age. Birds were divided in 8 treatments with 9 replicates of 3 hens each. The groups were fed the same basal diet and submitted to these dietary treatments: control, un-supplemented; green tea (GT), fed GT at 1 g/kg diet; brown marine algae (BMA), fed BMA at 1 g/kg diet; vitamin E (vit. E), fed vit. E at 300 mg/kg diet; GT+BMA, fed GT and BMA at 1 g/kg of each; GT+vit. E, fed GT and vit. E at 1 g and 300 mg/kg, respectively; BMA+vit. E, fed BMA and vit. E at 1 g and 300 mg/kg, respectively. Feeding BMA at 0.1% increased laying rate by 1.2% and improved feed conversion ratio by 5.2% compared to the control. Vitamin E significantly increased shell thickness by 6.6% and Haugh unit by 4.6% compared to the control. In addition, BMA+vit. E or GT+vit. E increased yolk colour by 9.1 and 10.7%, and Haugh unit of stored eggs by 10.9 and 11.1%. Cholesterol of fresh eggs and plasma were significantly decreased by 16.0 and 9.4% due to supplementation with BMA, and by 19.2 and 8.1% with vit. E addition. Plasma phosphorus increased by 19.1% after vit. E+BMA supplementation. In conclusion, use of BMA or vit. E or GT in laying hens diets which grow under heat stress is recommended as it improves production performance and egg quality.