Nutritional requirement of tryptophan for meat-type Japanese quails: Performance and carcass attributes

Tryptophan (Trp) as an essential amino acid for monogastric animals and preweaning ruminants plays crucial roles in physiological responses. An experiment was conducted to estimate the Trp requirements of quail chicks for optimum performance including body weight gain (BWG) and feed conversion ratio (FCR), and carcass attribute by different regression models. A total of 420, 21-day-old quail chicks were randomly allotted to one of seven experimental diets containing 2.12, 2.25, 2.38, 2.51, 2.64, 2.77, and 2.90 g Trp/kg from d 21 to 35. The treatments had 4 pen replicates and 15 birds each. Feed intake showed linear (P = 0.071) and quadratic (P = 0.078) increasing trend with increasing dietary levels of Trp during the whole of experiment. Feed conversion ratio, BWG, breast meat yield (BMY), thigh meat yield (TMY), edible section (ES) responded linearly or quadratically to graded levels of dietary Trp (P