Abstract:
The objective of this work was to determine the apparent ileal digestibility of calcium and phosphorus in broilers fed diets with different phytases and calcium:available phosphorus (Ca:aP) ratios. Two experiments were carried out: one with broilers with 22 to 33 days of age, and the other with broilers with 35 to 42 days. The Ca:aP ratios used were 4.5:1.0, 6.0:1.0, and 7.5:1.0 in the first period, and 3.5:1.0, 5.0:1.0, and 6.5:1.0 in the second. All diets were supplemented with 1,500 units of phytase activity per kilogram of six different sources of microbial phytase. At the end of each experiment, two broilers per replicate were slaughtered to collect the ileal content. In the samples of digested food, the Ca and P contents were determined for later calculation of the apparent ileal digestibility coefficients of these minerals. The Ca:aP ratio influenced the activity of phytases, and the highest digestibility was observed with lower ratios, in both experiments. The phytases that provided greater digestibility coefficients were A, D, and E. In both ages evaluated, the inclusion of phytases in the feed improved the digestibility of Ca and P, which was also affected by the content of calcium and by the phytase source used.
Index terms:
microbial enzymes; phosphorus digestibility; phytase superdosing; stages of creation