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Abstract
A 10 weeks experiment was conducted to investigate the effect of protease supplementation on the performance of 32 week’s old laying chickens fed marginally deficient protein diets in a completely randomized design. A total of 60 Isa Brown laying birds were allotted to 5 dietary treatments, six replicates of 2 birds each per replicate. The diets were formulated to contain 16% crude protein in Treatment 1 which was the control diet, T2- 5% CP reduction (15.2% CP), T3- 5% CP reduction (15.2% CP + 0.05% protease), T4- 10% CP reduction (14.4% CP) and T5- 10% CP reduction (14.4% CP + 0.05% protease). There were no significant differences (P>0.05) among all treatments on feed intake, haugh unit and hen-day egg production (HDEP) of the birds. The internal (albumen and yolk indices) and external (egg weight and length indices, shell thickness and weight) egg parameters showed significant increase in T3 and T5 (with protease inclusion at 5% and 10% CP respectively). It was concluded from the study that reduction of crude protein by 5% and 10% and inclusion of protease in the diet improved performance and egg quality parameters of Isa brown laying strains. It was however recommended that 10% CP reduction with protease inclusion gives optimum performance.