Effects of different levels of metabolizable energy and β-mannanase on egg quality and performance of laying hens fed diet based on corn-barley-soybean meal

A total of 216 white Hy-Line laying hens (57 wk of age) were used for 8-wk period to investigate the effect of different levels of energy and enzyme β-mannanase in the corn-barely-soybean based diet on performance and egg quality parameters. This experiment was conducted in a completely randomized design as factorial experiment (2 × 2) with 9 replicates. Treatments consisted of two levels of energy (2850 and 2750 Kcal/kg diet) and 2 levels of enzyme β-mannanase (with or without enzyme). The results showed that the the use of high-energy diets (2850 kcal/kg) in comparison with low-energy diets (2750 kcal kg) reduced feed intake 95. 6±3. 9 vs 97. 9±2. 0 g; P=0. 038) and increased yolk color index (5. 7±0. 6 vs 5. 1±0. 7; P=0. 044). However، other production traits and egg qualitaty parameters were not affected by dietary energy level. Although the effect of β mannanase enzyme on production parameters and egg quality traits were not significant، there were the trends for decreasing the percentage of broken eggs (P=0. 072) and improving eggshell thickness (P=0. 086) with supplementing β mannanase to the diet. Significant interactions between energy and enzyme were also observed in term of shell thickness during the whole experimental period، so that low-energy diet with enzyme significantly improved the eggshell thickness compared with low-energy diet without enzyme (P=0. 049). According to the results of current study، the use of β-mannanase enzyme is recommended to improve the eggshell quality characteristics in low-energy diet based on corn-barelysoybean diet.