Available online at www.pelagiaresearchlibrary.com Pelagia Research Library European Journal of Experimental Biology, 2011, 1 (4):169-172 ISSN: 2248 –9215 169 Pelagia Research Library The impact of supplemental L-threonine in broiler breeder molting hen diets on egg production, egg weight, and hatching traits Saeed Ashrafi 1 , Habib Aghdam Shahryar 1 , Abolfazl Gorbani 1 , Payam Panahi moghaddam and Mehdi Salmanzadeh 2 * 1 Departments of Animal Science, Shabestar Branch, Islamic Azad University, Shabestar, Iran 2 Young Researchers Club, Shabestar branch, Islamic Azad University, Shabestar, Iran ______________________________________________________________________________ ABSTRACT The impacts of supplemental L-threonine in broiler breeder molting hen diets were evaluated. 600 hens were obtained from (Cobb-500) broiler breeder strain at 60 weeks of age. All hens were collected from the same breeder flock and weighed on a balance with 10 g precision. At 60 weeks of age, hens based on a completely randomized design were divided into 5 treatments with 4 replicates per treatment and 30 hens and 3 roosters per replicate. Control hens were fed a corn-soybean commercial broiler breeder molting diet containing 0.48% threonine (Thr). Experimental diets containing, basal diet with 0.52, 0.57, 0.62, and 0.67% Thr were fed. Egg samples were analyzed for egg weight, egg production and hatching traits in newly-hatched chickens. The results of the study indicate that, egg production increased with increasing dietary threonine levels up to 0.67% Thr in the diet. But, the weight of eggs was significantly lower than control. Dietary L-threonine supplementation didn’t show any significant effect on hatchability of broiler breeder molting hens from 60 to 63 weeks of age. Weight of newly-hatched chickens was significantly lower when supplemental L-threonine in broiler breeder molting hen diets from 60 to 63 weeks of age were received than control group. These data clearly indicate a potential important impact on egg production by increasing dietary threonine nutrition of a broiler breeder molting hen. Key words: L-threonine, egg production, egg weight, hatching traits, broiler breeder molting hen. ______________________________________________________________________________ INTRODUCTION All nutrients needed for embryogenesis are provided by the hen by the time the fertile egg is laid [1]. If nutritional deficiencies occur during the formation of the egg, it can have significant repercussions on the developing embryo [2]. Hen diets are composed mainly of corn and soy, which contain low levels of L- threonine [3]. Therefore, eggs contain little or no L- threonine [4].