OPTIMAL METABOLIZABLE ENERGY AND CRUDE PROTEIN LEVELS FOR SINAI LAYING HENS

Abstract

Two experiments were conducted to investigate the effects of varying dietary energy and protein levels during laying period on productive and reproductive performance of local strain Sinai laying hens in order to get the best metabolizable energy and protein levels of such strain . In experiment 1, one hundred sixty five 25-week-old Sinai laying hens (150 females and 15 males) were randomly distributed into five equal experimental groups. They were fed five iso-caloric experimental diets (2700 kcal ME /kg) having different protein levels (16, served as a control, 14, 15, 17 or 18%). In experiment 2, three hundred 25-week-old Sinai laying hens were used in a 5x2factorial arrangement with 5 energy levels (2600, 2650, 2700, 2750 and 2800 kcal ME/kg) and 2 protein levels of 14 and 15%( the best result obtained from experiment 1 ). Each experiment lasted 24 weeks. In experiment 1, increasing dietary protein level from 14 to 18% did not significantly affect productive performance of hens, economical efficiency, egg quality, egg fertility and hatchability, digestibility of nutrients or blood constituents. In experiment 2, there was significant interaction effect between protein and dietary energy levels on total egg number, egg weight, egg mass, ash retention, digestibility of crude protein and ether extract. As dietary crude protein level increased from 14 to 15%, egg production rate, egg mass, feed conversion, economical efficiency, digestibility of organic matter, crude protein, ether extract and nitrogen- free extract were linearly increased. Neither dietary energy nor protein level affected body weight, egg weight, feed intake, egg quality, egg fertility and hatchability, N retention and digestibility of dry matter and crude fiber, and blood plasma parameters. From the practical and economical point of view, it can be concluded that the optimal dietary protein and metabolizable energy levels for Sinai laying hens are 15% CP and 2750 kcal ME/kg diet to achieve acceptable productive and reproductive performance.