Effect of microbial phytase on zinc bioavailability and cadmium and lead accumulation in growing rats.

This study evaluated the effect of increasing levels of dietary microbial phytase on the bioavailability of zinc and the accumulation of cadmium and lead in growing rats. Five groups of seven albino rats (initial average weight 47 g) were housed individually and fed phytate-rich diets (7 g/kg) based on maize, soya bean meal, corn starch and soya bean oil over a 4-week experimental period. The basal diet contained 24 mg zinc (native concentration), 10 mg lead as Pb(CH3COO)2.3H2O and 5 mg cadmium as CdCl2 per kg and was supplemented with 0, 250, 500, 1000 and 2000 U phytase from Aspergillus niger per kg diet. Supplementation of microbial phytase significantly increased apparent zinc absorption. Differences in zinc bioavailability due to supplementation of the diet with microbial phytase were evident in zinc concentration in plasma, femur and testes as well as in the percentage unsaturated plasma zinc binding capacity and the activity of the zinc metalloenzyme alkaline phosphatase. Cadmium concentrations in liver and kidneys were not significantly altered in response to the different dietary treatments. There was a tendency for femur lead concentration to be increased in response due to the phytase supplementation.