The effects of dietary oil and methionine on performance and egg quality of commercial laying hens during summer season

The present experiment was conducted to determine the effects of supplemental oil and methionine on performance and egg, quality of laying hens from two commercial strains (white and brown) at high summer temperature. A 2 x 2 x 3 factorial arrangement consisting of two strains of commercial laying hens (white and brown), two levels of supplemental methionine (0 and 1 g/kg) and three levels of supplemental soybean oil (0, 20 and 40 g/kg) were used in this study. Thus, six experimental diets were formulated on isoenergetic and isonitrogenous basis. White layers had higher egg production (EP) and Haugh Units (HU) but lower egg weight (EW), shell weight per unit surface area (SWUSA), feed intake (FI) and feed conversion (FC) than brown ones. Both in brown and white layers, methionine supplementation increased EP and improved FC, but decreased EW and FI. EP was not significantly affected in white layers by dietary oil. However, it slightly increased in brown layers fed low oil (20 g/kg) diet. EW increased in both strains with soybean oil. The improvement in EW was more pronounced at the level of 20 g/kg oil supplementation than at the level of 40 g/kg. SWUSA was significantly decreased by adding oil. HU was increased significantly at 40 g/kg oil supplementation but FI intake did not change significantly.