Effect of phytase and protease supplementations on growth performance and carcass characteristics of broiler chickens fed suboptimal levels of crude protein

Two hundred and seventy (270) day old unsexed Arbor Acre broiler chicks were assigned to nine dietary treatments comprising three replicates of 10 chicks each. During the starter phase birds were fed the control 23% crude protein (CP) without enzyme (T1), 21% CP without enzyme (T2), 21% CP plus phytase (PHY) (T3), 21% CP plus protease (PRO) (T4), 21% CP plus PHY and PRO (T5); and 19% CP without enzyme (T6), 19% CP plus PHY (T7), 19% CP plus PRO (T8), 19% CP plus PHY and PRO (T9). Phytase and protease supplementation followed the same arrangement in all the phases, but the crude protein were 23, 20 and 18% CP (in T1); 21, 18 and 16% CP (in T2, T3, T4 and T5) and 19, 16 and 14% CP (in T6, T7, T8 and T9) during starting, growing and finishing phases respectively. Feed and water were given unrestrictedly. The feed intake and weights of birds were recorded on weekly basis. Nutrient digestibility was determined at each phase and carcass evaluation was done at the end of the experiment. From 0-56 days, PHY supplementation significantly (P < 0.05) improved final body weight and daily weight gain in suboptimal CP diets (T3). Enzymes had no significant effect on the carcass characteristics except drumstick, which was highest (P < 0.05) on PRO treatments. The addition of phytase or protease alone and in combination increased the available nutrient levels and there was a significant effect of enzymes supplementation on nutrient digestibility. It could be concluded that phytase, protease and their combination improved performance, nutrient digestibility and carcass cut part of broiler chickens fed suboptimal crude protein diets.Keywords: Feed additives; enzymes; suboptimal crude protein; carcas