Phytate Degradation in the Gizzard is Pivotal to Phytase Responses in Broiler Chickens

Positive control (PC) and negative control (NC) maize-based diets were supplemented with either 0 and 1000 or 0, 500 and 2000 FTU/kg Buttiauxilla phytase, respectively, and offered to broilers from 7 to 28 days post-hatch. Degradation of IP6 phytate was determined in five gastrointestinal segments (gizzard, proximal jejunum, distal jejunum, proximal ileum, distal ileum) using acid insoluble ash as the dietary marker. A phytate degradation coefficient of 0.955 was recorded in the gizzard of birds offered the NC + 2000 FTU/kg diet. Curiously, 0.527 phytate degradation was observed in non-supplemented NC diets, which suggests a net phytate degradation of 0.428 to exogenous phytase. Across all five treatments, however, gizzard phytate degradation coefficients were significantly correlated with weight gain and toe ash, which was not the case in four small intestinal segments. Therefore, this study demonstrates that phytate degradation in the gizzard is pivotal to the magnitude of responses generated by phytase.