Effect of phytate on laying hen performance, carbonic anhydrase activity and total cholesterol level.

Phosphorus is an indispensable mineral, crucial to growth and development both structurally and metabolically but phytate (a major storage form of phosphorus in seeds of plants) decreases mineral bioavailability and nutrient digestibility. Subsequently, in determining the influence of phytate with/without phytase or citrate on laying performance, 5 soybean-maize based diets of similar nutrient density were formulated: a control diet with 0.21% phytate-P and 0.36 % nonphytate-P but no added phytate, and a second similar diet except that the inorganic phosphorus source was replaced by added phytate-P. The third, fourth and fifth diets were similar to the second diet but they contained 0.3% phytase, 1.5% citrate, 0.3% phytase plus 1.5% citrate, respectively. Each treatment was randomly assigned to 35-week-old laying hens. Hens fed the phytase diet showed a pronounced increase in egg production (P 0.05), egg weights were affected (P 0.05). Both phytase and phytase plus citrate treatments yielded high serum and yolk total cholesterol, followed by the citrate and phytate-P, and the least for the control diet. Supplementary phytase and/or citrate seems to increase nutrients availability. Whether citrate increases susceptibility of phytate to phytase by removing cations bound to phytate or creating digesta pH conducive for phytate hydrolysis is yet to be determined.