M. Zaghari - Department of Animal Science, College of Agriculture, University of Tehran, Karaj, Islamic Republic of Iran.
S. Maghami Tekieh - Islamic Azad University, Maragheh Branch, Maragheh. Islamic Republic of Iran.
A. Safamehr - Islamic Azad University, Maragheh Branch, Maragheh. Islamic Republic of Iran.

One hundred ninety two broiler breeder hens, from ۴۰ to ۴۹ weeks of age, were utilized in a precision feeding study for determining the hens’ energy requirement. Treatments were daily feed allotments containing metabolizable Energy Requirement (ER) estimated by empirical model, ER minus ۱۰ (ER‒۱۰), plus ۱۰ (ER+۱۰), and plus ۲۰ kcal hen-۱ d-۱ (ER+۲۰). Four levels of Metabolizable Energy Intake (MEI) were made by adding ۰, ۱.۲, ۲.۴ and ۳.۶ grams corn oil, over the top of daily feed allotment. All birds consumed the same amount of diet, and were provided the same intake of nutrients, except energy. Hens with weight gain of ۳.۵ g per day had the maximum reproductive performance. Ovary weights were lower in ER-۱۰ hens. This difference was also reflected in Small Yellow Follicle (SYF), and Large Yellow Follicle (LYF) numbers, in which the ER-۱۰ hens had fewer SYF (۷.۶) and LYF (۱.۱). Hens that received ۴۶۲.۷ kcal d-۱ (ER), produced ۴.۰۴ eggs more than those that received ۴۵۲.۷ kcal d-۱ (ER‒۱۰). However, addition of extra ۱۰ and ۲۰ kcal (ER+۱۰, ER+۲۰) on daily MEI had no beneficial effect on egg production. Using the linear broken line model, the ME requirements for egg production and hatchability were estimated at ۴۵۸.۵, and ۴۵۶.۲ kcal hen-۱ d-۱, respectively. Comparing the current estimated requirement value with earlier reports revealed that broiler breeder hens need more energy in a commercial house than those kept in an experimental house in the cage or pen. In conclusion, during post peak period with average ۴۵۸.۵ kcal MEI, ۵ kcal hen-۱ d-۱ more than Ross ۳۰۸ recommendation can improve broiler breeder hens’ performance.

Egg production, Ross ۳۰۸, Yellow follicle, Hen’s energy requirement