Dietary phytase and protease improved growth and nutrient utilization in tilapia (Oreochromis niloticus x Oreochromis aureus) fed low phosphorus and fishmeal-free diets

A 10-week study was conducted to evaluate the effects of supplemental phytase and protease in low phosphorus (LP) and fishmeal-free diets (FMF) on growth and nutrient utilization of tilapia. Seven isonitrogenous diets were prepared as positive control diet (PC) containing 60 g/kg fishmeal and 18 g/kg monocalcium phosphate (MCP), LP diet (12 g/kg MCP), FMF diet, LP-FMF diet, and three enzyme diets with phytase (LP + Ph), protease (FMF + Pr), and phytase + protease (LP-FMF + Ph + Pr) supplementation in LP, FMF and LP-FMF diets, respectively. Weight gain, nutrient (except Ca) retention and digestibility of LP, FMF and LP-FMF groups were lower than those of PC group (p < 0.05). Compared to LP, FMF and LP-FMF groups, the supplementation of phytase, protease and phytase + protease improved WG by 13.2%, 11.1% and 13.0% (p < 0.05). The three enzyme groups showed higher digestibility of protein and P, and higher intestinal villus length than those of LP, FMF and LP-FMF groups (p < 0.05), respectively. Dietary phytase and Ph + Pr also promoted the retentions of crude protein and P (p < 0.05). The results indicated that the supplementation of phytase in LP diet and protease in FMF diet improved the growth and nutrient utilization, and phytase reduced MCP inclusion in the diet of tilapia.