Interaction between dietary protein and critical amino acids on performance of birds developed for free range farming during juvenile phase.

Vanaraja, a dual-purpose chicken variety needs intensive farm conditions to protect against cold, nutrient deficiencies and to provide immunity during the initial 6 weeks of age before letting them under free range conditions. Therefore, 2 separate experiments were conducted to identify optimum dietary levels of crude protein (CP), sulphur amino acids (SAA) and lysine (Lys) in diets of Vanaraja chicken from 1 to 42 days of age. Diets (9) were prepared with 3 levels of CP (14.5, 16 and 17.5%) and SAA (0.567, 0.626 and 0.685%) in a factorial manner and each diet was fed to 8 replicate groups of 6 chicks each in experiment 1. Similarly, 6 diets with 2 levels of CP (14.5 and 16%) and 3 levels of Lys (0.66, 0.73 and 0.79%) were prepared and each diet was fed to 12 replicate groups in experiment 2. The interaction between CP and SAA significantly influenced the body weight gain and feed conversion efficiency at 28 days of age. However, weight gain and feed efficiency at 14 and 42 days of age, relative weights of ready to cook yield (RTC), abdominal fat, gizzard, liver, giblet, intestine and lymphoid organs (bursa and spleen), and the antibody titres against sheep red blood cells (SRBC) and CBH response to phytohaemoglutanin-P (PHA-P) inoculation were not affected by the interaction between these 2 nutrients. Antibody production against SRBC was significantly higher in birds fed 17.5% CP compared to lower levels. Abdominal fat content decreased with increase in dietary CP. The interaction between CP and Lys did not influence weight gain, feed efficiency (at 14, 28 and 42d of age), RTC yield, abdominal fat, relative weights of gizzard, liver, giblet, bursa and spleen. Relative weight of abdominal fat and giblet decreased with increase in concentration of CP in diet. The relative weights of liver and giblet increased non-linearly with increase in Lys content in diet. Based on the results of both the experiments, it is concluded that Vanaraja chicks do not require more than 14.5% crude protein, 0.567% sulphur amino acids and 0.66% lysine for optimum performance and carcass traits during 1 to 42 days of age