Functionality of a next generation biosynthetic bacterial 6-phytase in enhancing phosphorus availability to broilers fed a corn-soybean meal-based diet

Abstract

The addition of phytase enzyme to broiler feed as a means of improving phosphorus (P) availability and reducing P excretion is widespread practice. New phytases with enhanced functionality continue to be developed. We tested the effects of a next generation biosynthetic bacterial 6-phytase on growth performance, tibia ash and P digestibility in broilers. Treatments included a nutritionally adequate positive control (PC) diet, a negative control (NC) diet formulated with reductions in Ca and available P (avP) of 2.0 g/kg and 1.9 g/kg (starter phase) and 2.0 g/kg and 1.8 g/kg (finisher phase), respectively, and three further diets comprising the NC supplemented with three levels of phytase (250, 500 or 1000 FTU/kg). Diets were fed in mash form to day-old Cobb 500 broilers housed in pens (9 pens for NC, 10 pens for all other treatments; 24 birds/pen), in two phases (starter, days 1–21; finisher, days 22–42). Tibias were collected from 4 birds on day 21 and from 6 birds on day 42 for determination of defatted tibia ash. Ileal digesta was collected on day 21 for determination of apparent ileal digestibility (AID) of nutrients. Compared to PC, the NC exhibited reduced tibia ash at day 21 and 42, resulting in reduced average daily gain (ADG) and average daily feed intake (ADFI) during starter, finisher, and overall phases, and increased feed conversion ratio (FCR) during finisher phase and overall (P < 0.05). Phytase at any dose-level during both phases improved tibia ash vs. NC (P < 0.05) and maintained feed intake and growth parameters equivalent to the PC. At a dose-level of 500 FTU/kg or above, phytase supplementation increased AID of P vs. NC (P < 0.05) and at 1000 FTU/kg, phytase improved the AID of P compared with PC (P < 0.05). For all measures, response values were numerically highest with 1000 FTU/kg and increased linearly or quadratically with increasing phytase dose (P < 0.05). Phytase at 1000 FTU/kg produced birds with an average day 42 body weight of 2.74 kg and overall FCR of 1.626, comparable to PC. On a grams per kilogram diet basis, phytase at 1000 FTU/kg improved ileal digestible P by 1.76 g/kg above NC (at day 21). This is equivalent to 2.07 g P from monocalcium phosphate (MCP-P), based on digestible P improvement. The results suggest the novel biosynthetic phytase has high functionality in the tested dietary setting.