Effect of dietary [beta]-mannanase on productive performance, egg quality, and utilization of dietary energy and nutrients in aged laying hens raised under hot climatic conditions

Objective: The objective of this experiment was to investigate the effect of dietary [beta]-mannanase on productive performance, egg quality, and utilization of dietary energy and nutrients in aged laying hens raised under hot climatic conditions. Methods: A total of 320 84-wk-old Hy-line Brown aged laying hens were allotted to one of four treatments with eight replicates in a completely randomized design. Two dietary treatments with high energy (HE; 2,800 kcal/kg nitrogen-corrected apparent metabolizable energy [[AME.sub.n]]) and low energy (LE; 2,700 kcal/kg [AME.sub.n]) were formulated. Two additional diets were prepared by adding 0.04% (MN4) or 0.08% [beta]-mannanase (MN8) to LE treatment diets. The feeding trial was conducted for 28 d, covering a period from July to August in South Korea. The average daily room temperature and relative humidity were 29.2[degrees]C and 83%, respectively. Results: Productive performance, egg quality, and cloacal temperature were not influenced by dietary treatments. The measured [AME.sub.n] values for MN8 diets were similar to those for HE diets, which were greater (p