Effect of Diets Formulated on the Basis of Four Critical Essential Amino Acids on Performance and Blood Biochemical Indices of Broiler Finisher Chickens Reared under Tropical Environment

A study was conducted in a completely randomized design to evaluate the effect of diets formulated on the basis of four critical essential amino acids (lysine, methionine, tryptophan and threonine) on the crude protein requirement, carcass quality, nutrient digestibility, haematological and blood biochemical indices of broiler finisher chickens (28-56 days) reared under tropical environment. One hundred and eighty chickens were used in this experiment. There were four experimental diets each with three replicates (15 birds per replicate). The experimental diets were formulated with a gradual crude protein increase from 18 to 21% in 1% intervals. Diet 1, 2, 3 and 4 contained 18, 19, 20 and 21% dietary crude protein, respectively. Ileal digestible quantities of all essential amino acids (EAA) were almost equal in the diets and total amount of each EAA was maintained at or above NRC requirements. The performance of chickens fed 19% crude protein (CP) was similar to chickens fed 20 and 21% CP diets in terms of final weight, weight gain and feed conversion ratio. Feeding 18% CP with essential amino acids resulted in significantly (P