Abstract:
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
