Influence of microbial phytase on nutrient digestibility, growth performance, geometric bone characteristics, and expression of calcium and phosphate homeostasis genes in broiler chickens

Phytases are commonly used in broiler feed to break down phytic acid and release nutrients. This study evaluated the effects of microbial phytase on nutrient digestibility, growth performance, bone characteristics, and calcium/phosphate homeostasis in broilers. Six treatment groups of 576 Cobb 500 chicks were fed a control diet (T1) and diets supplemented with 200–600 FTU/kg of phytase (T2–T6). Diet phases included starter, grower, and finisher diets over five weeks. Results showed no significant growth differences in the starter phase, but birds receiving phytase showed improved feed intake, body weight, and feed conversion in the finisher phase (P < 0.001). Nutrient digestibility, including protein, calcium, and phosphorus, significantly improved (P < 0.001) with increased phytase levels. Tibia bone weight, length, and strength increased (P < 0.01), while medullary canal diameter was larger in control birds (P < 0.001). Gene expression related to calcium/phosphate homeostasis did not differ in starters, but FGF23 and VDR genes significantly varied in finishers (P < 0.05). Tibia mineral composition was significantly enhanced in phytase-supplemented groups (P < 0.001). Among treatments, 400 FTU/kg provided optimal performance and cost-effectiveness. In conclusion, microbial phytase enhances nutrient availability, improves bone mineralization, and may reduce environmental phosphorus excretion.