Protein requirement of Japanese quail (Coturnix coturnix japonica) during rearing and laying periods

Two completely randomized trials were conducted to estimate protein requirements of Japanese quails during the rearing and laying periods. In each trial, 150 quails were distributed in five treatments with five repetitions. Crude protein levels in the rearing period were 18, 20, 22, 24 and 26% (Trial 1) and during the laying period were 16, 18, 20, 22 and 24% (Trial 2). A quadratic effect of protein level was observed on weight gain from seven to 35 days (Trial 1). There were no effects of protein levels on feed intake and feed conversion. Protein levels in experimental diets during rearing had no effect on egg production up to 63 days. However, laying was delayed and variation in body weight was greater in quails fed lower protein levels. In Trial 2, a quadratic effect of protein levels was seen on egg production and feed conversion; and a linear effect was seen on mean egg weight and feed intake. Crude protein levels of 23.08% and 21.95% were estimated by regression equations for rearing and laying, respectively.