Effects of phytase and protease supplementation, with and without considering their nutritional matrix values, on the productive performance of laying hens during the late‑lay period.

This study investigated the effects of phytase and protease supplementation, with or without considering their nutritional matrix values, on 384 Hy-Line W-80 laying hens at 63 weeks of age. The experiment was conducted as a 2×2×2 factorial arrangement in a completely randomized design with eight treatments and six replicates of eight birds each. The trial lasted 10 weeks, during which performance parameters, internal egg quality, eggshell traits, selected blood metabolites and ovary status were evaluated. Results showed that protease supplementation in diets without phytase increased (P<0.05) egg production, and egg production was also higher (P<0.01) with on-top enzyme supplementation. Egg weight, egg mass, and feed conversion ratio were not affected (P>0.05) by any main or interaction effects. Protease supplementation increased (P<0.05) the Haugh unit and yolk color score. The three-way interaction of phytase, protease, and consideration of their nutritional matrix significantly affected eggshell thickness and calcium content. When phytase was used alone, considering its nutritional value increased eggshell thickness (P<0.01) and calcium content (P<0.05) compared with on-top supplementation. In addition, matrix-based phytase supplementation improved (P<0.05) shell strength. Eggshell phosphorus concentration was also higher (P<0.05) in diets supplemented with protease in the absence of phytase. Total antioxidant capacity increased (P<0.05) with matrix-based phytase supplementation. Dietary protease supplementation resulted in higher (P<0.05) plasma total antioxidant capacity and plasma luteinizing hormone level. Overall, phytase and protease supplementation may benefit laying hens, but responses depend on whether their nutritional matrix values are considered during diet formulation and on their combined use.