Effect of β-mannanase supplementation in low-energy diets containing palm kernel meal on productive performance, egg quality, intestinal morphology, and liver characteristics in laying hens raised under heat stress conditions.

Objective: This study aimed to investigate the effect of β-mannanase (MN) supplementation in low-energy diets containing palm kernel meal (PKM) on productive performance, egg quality, intestinal morphology, and liver characteristics in laying hens under heat stress (HS) conditions.

Methods: Four hundred 37-wk-old Hy-Line Brown laying hens were randomly allotted to 5 dietary treatments with 8 replicates for 8 wks of the feeding trial conducted under a cyclic HS condition. The positive control (PC) diet was prepared, whereas the low-energy negative control (NC) diet was formulated to contain decreased AMEn by 100 kcal/kg than PC diets. An additional low-energy diet was prepared by including 5.0% PKM, and it was supplemented with either 0.05% or 0.10% MN.

Results: Feeding low-energy diets containing PKM increased (p < 0.05) feed conversion ratio (FCR), but MN supplementation did not affect FCR in laying hens under HS conditions. Egg yolk color was improved (p < 0.05) by feeding low-energy diets containing PKM, regardless of MN supplementation with no differences in other egg quality among treatments. The supplementation of 0.10% MN in PKM-containing low-energy diets showed lower (p < 0.05) blood heterophil to lymphocyte ratio (H:L) ratio than NC diets, but exert blood H:L ratio comparable to PC diets. A linear trend for increased villus height (VH) was observed (p < 0.05) by increasing MN supplementation in PKM-containing low-energy diets with the greatest VH was found in 0.10% MN supplementation.

Conclusions: Feeding low-energy diets containing 5.0% PKM decreased feed efficiency in laying hens under HS conditions. However, MN supplementation in PKM-containing low-energy diets had no beneficial effects on laying performance. Low-energy diets, irrespective of PKM inclusion, exacerbate stress responses and impair jejunal morphology. However, 0.10% MN supplementation in PKM-containing low-energy diets ameliorated stress responses and improved jejunal morphology in laying hens under HS conditions.