THE EFFECTS OF 1,25-DIHYDROXYCHOLECALCIFEROL AND PHYTASE ON THE NATURAL PHYTATE PHOSPHORUS UTILIZATION BY LAYING HENS

Two experiments were conducted to investigate the effects of supplemen ting a corn-soybean layer diet with either phytase, 1,25-dihydroxychol ecalciferol [1,25-(OH)(2)D-3], or their combination. The basal diet wa s formulated to contain 3.00% Ca and 0.33% total P. In Experiment 1, 1 60, 56-wk-old laying hens were randomly assigned to treatment groups f ed either the basal diet alone or diets supplemented with either 600 p hytase units (ETU) per kilogram feed, 5 mu g 1,25-(OH)(2)D-3/kg feed, or their combination for an experimental period of 9 wk. Experiment 2 had the same design and treatment groups except that laying hens 24 wk of age were used for 8 wk. In both experiments, phytase had a positiv e effect on BW and increased plasma dialyzable P, tibia bone ash, and phytate P retention. In the first experiment, the addition of phytase, 1,25-(OH)(2)D-3, or their combination prevented a rapid decrease in e gg production due to a Mycoplasma gallisepticum infection observed in hens fed the basal diet. However, no benefit in egg production was obt ained in the second experiment. No effects on egg weight and egg speci fic gravity were observed in both experiments. These results clearly i ndicate that phytase, and to a lesser extent 1,25-(OH)(2)D-3, can be u sed to increase the utilization of phytate P by laying hens.