The effect of phosphorus, phytase enzyme, and calcium on the performance of layers fed corn-based diets

An experiment employing a factorial arrangement of two levels of Ca, two le vels of available P (AP), and three levels of phytase enzyme was carried ou t with 360 ISA White layers from 18 to 67 wk of age. The Ca levels were mai ntained at 3.7 and 4.0% throughout the experiment. The AP levels were 0.2 a nd 0.4% for the high and low treatments until 55 wk of age and were reduced to 0.11 and 0.22% thereafter. Phytase enzyme levels were 0, 250, and 500 p hytase units (FTU)/kg of feed. In the period before Week 55, either level o f AP was likely adequate for maximum production. However, when lower levels of AP were fed after this time, low AP was associated with reduced BW and egg production, and enzyme supplementation was able to compensate for low A P. In this period, high AP and the highest level of phytase produced negati ve effects on BW, egg weight, and the feed conversion ratio. The ratio of C a to AP was important; shell quality was best with high or low levels of bo th. With high levels of Ca, enzyme supplementation compensated for low leve ls of AP and overcompensated with a high level of AP. These effects were re duced or absent with low levels of Ca. It is clear from this study that phy tase enzyme can compensate for low levels of AP in diets based on corn and soybean meal, but that the optimum level of supplementation depends as well on the Ca level.