Genetic Selection for Body Weight in Japanese Quail (Coturnix coturnix japonica) Under Different Nutritional Environments

J apanese quail used in poultry industry for its meat and egg production due to many features such as low feed intake, low rearing area requirements, low breeding cost and high disease resistance (Narinc et al., 2010).Based on these advantages, the reared number of quails is gradually increasing in the world poultry industry as a valuable source for eggs and meat production.Commercially, quails are produced mainly for meat production in Europe countries and for egg production in Japan and used as a dual-purpose birds in many Asian countries (Minvielle, 1998).The National Research Council recommendations of crude protein was 24 % for growing Japanese quails (NRC, 1994).Global environment suffering from pollution from ammonia emission and nitrogen excretion from poultry industry, beside that the protein being the most expensive diet component which affect the total cost of production, so the recent trends are decreasing the protein levels in poultry diets without significant effects on production performance.Wen et al. (2017) recorded that quails reared on diets with crude protein range 17.61-25.32% had no significant influence on carcass yield at 42 days of age.Most breeding programs that aimed to improve meat production are focused on increase live body weight and feed intake at fixed ages, and most studies carried out to increase the body weight in early periods using genetic selection which represent an important tool for genetic improvement in animal breeding program (Hassan, 2011; Fadhil and Hassan, 2018) or using outbreeding mating system between lines to get heterosis in the next generation (Hassan and Ali, 2017).Phenotypic selection used research