A novel consensus bacterial 6-phytase variant added to phytate-rich diets totally replaced inorganic phosphate in broilers

Abstract

The capacity of a novel bacterial 6-phytase variant (PhyG) to totally replace dietary supplemental inorganic phosphate (Pi) in broilers aged one day old was evaluated using a phased dosing strategy and reduction in dietary phytate. A total of 1,248 one-day-old Ross 308 broilers were assigned to 24 pens (52 birds/pen, 12 pens/diet, six each males and females) in a complete randomised block design with a 2×2 factorial arrangement (two diets, two genders). Diets comprised: (1) a positive control (PC) based on maize, wheat and soybean meal, containing Pi from monocalcium phosphate and 2,000 XU/kg xylanase, and; (2) an inorganic phosphate-free (IPF) diet equivalent to PC but with reduced Ca (-2.0 g/kg) and supplemented with PhyG at 3,000, 2,000 and 1000 FTU/kg from d 0 to 11 (3.4 g/kg phytate-P (PP)), d 11 to 22 (3.3 g/kg PP) and d 22 to 42 (2.8 to 2.9 g/kg PP), respectively. A negative control was not included for animal welfare reasons. Tibias were collected on d 11, 22 and 42 from two birds/pen. Treatment IPF maintained or improved average daily gain (ADG), average daily feed intake and feed conversion ratio (FCR) vs PC during all phases; Body weight was higher in the IPF treatment than the PC at d 42 (+3.97%, P<0.01) and ADG during d 0 to 42 (+4.10%, P<0.01). Overall (d 0 to 42), treatment IPF improved FCR in males (-5 points vs PC, P<0.05) but not females. Tibia ash was equivalent in IPF and PC throughout, with no gender differences. In conclusion, when applied as a phased dosing strategy to diets with graded reduction in PP content, PhyG totally replaced supplemental Pi during all growth phases in males and females.