Effects of Low-Protein Diets Supplemented with Essential Amino Acids on Growth Performance, Meat Quality, and Nitrogen Retention in Growing Japanese Quails

One experiment was carried out to investigate the effect of low crude protein (CP) diets supplemented with crystalline essential amino acids (EAAs) on growth performance, meat quality, and nitrogen retention in Japanese quails reared from 1 to 35 days of age. A total of 840 unsexed one-day-old quail chicks were used in a completely randomized design consisting of seven treatments with six replicates and 20 birds in each. In addition to the control diet, two negative control diets were also adjusted to contain 10 and 20% lower CP than the control (LP10 and LP20 diets, respectively). The EAAs/CP ratio was similar to that of the control diet. Also, four rations supplemented with amino acids were formulated to contain 10% (LP10+EAAs10 and LP20+EAAs10) or 20% (LP10+EAAs20 and LP20+EAAs20) higher EAAs than LP10 and LP20. Crude protein digestibility was determined using the total collection method at 21 and 35 d of age. After slaughtering at 21 and 35 d of age, whole-breast meats were dissected out to determine meat quality indices. During 1 - 21d of age, 10 or 20% reduction in CP significantly decreased body weight gain and increased feed conversion ratio; however, amino acid supplementation significantly improved body weight gain and feed conversion ratio (P < 0.05). During 1- 35 d of age, reduction of CP to 20% led to decreased body weight gain in EAAs supplemented and un-supplemented diets. Dietary treatments did not have any significant effect on the breast meat quality variables except for pH. At 35d of age, 20% reduction in dietary CP significantly reduced nitrogen retention percentage. Overall, a 10% reduction in dietary CP without EAAs supplementation had no adverse effect on the growth performance of Japanese quails during the 1 to 35d of age.