Effect of dietary supplementation of microbial protease on performance, egg quality and nitrogen retention in white leghorn layers

Context Protease supplementation increases the digestibility of protein, which enables reduction in the requirement of crude protein (CP) in the diet for optimum performance and egg quality in laying chickens. Aims An experiment was conducted to study the effects of protease supplementation (0 and 4000 u/kg) in diets containing three graded levels of CP on egg production, egg quality and nitrogen retention in layers. Methods Three diets with 15, 16.5 and 18% CP with uniform metabolisable energy (10.67 MJ/kg) were prepared. Each diet was supplemented with (4000 u/kg) or without protease in a 3 × 2 factorial arrangement. Each diet was fed ad libitum to six replicates consisting of 88 white leghorn laying chickens in each from 53 to 72 weeks of age. Key results Supplementation of protease significantly (P < 0.05) improved performance (egg production, feed efficiency and bodyweight) and egg albumen quality (Haugh unit score). Layer performance was not affected by reducing the dietary CP from 18 to 15%. The interaction between CP level and protease supplementation did not influence the laying performance and egg quality parameters studied. Nitrogen retention reduced significantly (P < 0.05) with increase in dietary CP level from 15 to 18%. Supplementation of protease significantly (P < 0.05) improved the N retention. Conclusions The results suggested that 15% CP was adequate for optimum layer performance during the latter part of egg production phase (53 to 72 weeks of age). Protease supplementation improved the layer performance, egg albumen quality and nitrogen retention. Implications The results of this study will contribute for optimisation of dietary protein level in layer diet. Utilisation of dietary protein can be enhanced with protease supplementation which results in enhanced egg production and albumen quality in egg laying chickens.