Effect of phytase dose and reduction in dietary calcium on performance, nutrient digestibility, bone ash and mineralization in broilers fed corn-soybean meal-based diets with reduced nutrient density

•Buttiauxella phytase at 1000 FTU/kg improved BWG, FCR vs. 500 FTU/kg during 0 to 21d.•Phytase supplementation enhanced ileal and total tract digestibility of P and ca.•Increase Ca reduction level with phytase increased ileal P and Ca digestibility.•Increase Ca reduction level improved feed efficiency in diets containing phytase.•All phytase treatments reduced feed cost and improved energy efficiency vs. PC.