Abstract
Experiments were conducted to investigate the effect of supplementation of different sources of vitamin D on the transfer of vitamin D to the egg yolk. Vitamin D2-fortified shiitake, pure vitamin D2 and pure vitamin D3 were used as a source of vitamin D. Experimental diets contained each source of vitamin D at the level of 500μg/kg as the amount of vitamin D in the basal diet. Laying hens (White Leghorn) were divided into three groups of five birds each and fed the experimental diets for 14 days. The initial contents of vitamin D2 and vitamin D3 in the egg yolk were undetected and 0.05μg/g, respectively. At the end of the experiment, vitamin D2 and vitamin D3 contents (μg/g) in the egg yolks were as follows: 0.326, 0.080 on the shiitake diet; 0.277, 0.055 on the vitamin D2 diet and undetected, 0.494 on the vitamin D3 diet. The transfer ratio of vitamin D (total amount of vitamin D2 and vitamin D3) to the egg yolk on the shiitake, vitamin D2 and vitamin D3 diets were 10.9%, 8.8% and 12.7%, respectively. The transfer ratio of vitamin D3 tended to be higher than that of vitamin D2. The content of 25-OH-D3 in the egg yolks on the vitamin D3 diet increased three-fold during the experimental period, and 25-OH-D2 was detected in the egg yolk on the shiitake diet and vitamin D2 diet. However, the content of 25-OH-D2 in the egg yolk was significantly lower than that of 25-OH-D3. There was no effect of the different sources of vitamin D on the performance, egg shell quality and concentrations of calcium and phosphorus in the plasma of laying hens.
