Requirement of critical Amino acids for growth and maintenance of naked neck broiler chickens in extreme summer

The requirements of critical amino acids (CAA) in extreme summer (31.6–36.30°C) were worked out involving 192 chicks distributed into 24 groups. The birds were reared on a standard diet upto 3 weeks of age. Eight dietary treatments (4 dietary regimens-DR x 2 protein type) were formulated following factorial design. The dietary regimens were CP (20%) and 3200 ME (DR1) as per NRC (1994), 100% AA of NRC and 3200 kcal ME (DR2), 108% AA of NRC and 3000 kcal ME (DR3), 94% AA of NRC and 3000 kcal ME (i.e CAA levels adjusted to 3000 kcal ME/kg-DR4) with FM or with all vegetable protein meal. Each diet was offered to triplicate groups of 8 birds each from 3 to 6 weeks of age. The data were also fitted into different regression models for partitioning of critical amino acids for maintenance and gain. The body weight gain was higher (P<0.01) in high and medium energy and high CAA diets. Feed intake was higher (P<0.01) in high-energy diets. Feed conversion ratio was not different (P>0.05) among dietary treatments. The ME requirement per kg gain was lower (P<0.05) in high CAA and low energy diet, however, protein efficiency and feed cost per kg gain was lower (P<0.001) in high-energy diet. The maintenance requirements of lysine, methionine and threonine were 496.0±34.0, 189.0±13.0 and 374.0±25.0 mg/kg W^0.75, while the corresponding values for body weight gain were 9.28±1.00, 3.54±0.10 and 6.77±0.10 mg/g, respectively. The R² values for corresponding estimates were 0.996, 0.995 and 0.996. The requirements of lysine, methionine and threonine for naked neck finisher broilers (3–6 weeks of age) were worked out to be 0.91, 0.345 and 0.671 percent through linear model and 0.958, 0.357 and 0.704 percent through quadratic model, respectively, for summer months.