Various Levels of Calcium and Phosphorus Diets in Response to 1, 25 – Dihydroxycholecalciferol in Laying Hens

The effect of 1,25-dihydroxycholecalciferol [1,25-(OH)2 D3 ] supplementation on laying hen diets was evaluated using diets high and low in Ca (3.0% and 1.8% ) and high and low in P( 0.52% and 0.33% ). Since two levels of 1,25- (OH)2 D3 supplementation (0 and 5 μg/kg diet ) were applied, the experiment was a 2 X 2 X 2 factorial arrangement in a completely randomized design using nine individually housed hens per each 8 treatments (72 in total). The hens were fed the diets for 28 days and records were kept on body weight, egg production, feed intake, egg weight, and egg specific gravity. At the end of the experiment,the hens were bled for plasma Ca and P determination and after being euthanased the left tibia removed for bone ash measurement. The corn-soybean meal based diet contained 0.1% Cr2O3 as an indicator for determining Ca, P and phytate phosphorus retention at 14 and 28 days. 1, 25-Dihydroxycholecalciferol supplementation had no effect on hen weight, egg production or feed intake. However, large increases in egg specific gravity were obtained when 1, 25-(OH)2 D3 was fed to hens receiving the low Ca diet. All of the treatments had significant effects on bone ash. The greatest effect of 1, 25-(OH)2 D3 on bone ash was obtained in those hens fed the high Ca and P diet that was then supplemented with 1,25-(OH)2 D3 (49.3% vs 53.9% bone ash). At day 14, the high Ca diets decreased phytate P retention while at d 28 the high P diets decreased phytate P retention