Effect of different sources of vitamin D on transfer of vitamin D to egg yolk

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 D-2-fortified shiitake, pure vitamin D-2 and pure vitamin D-3 were used as a source of vitamin D. Experimental diets contained each source of vitamin D at the level of 500 mu g/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 D-2 and vitamin D-3 in the egg yolk were undetected and 0.05 mu g/g, respectively. At the end of the experiment, vitamin D-2 and vitamin D-3 contents (mu g/g) in the egg yolks were as follows: 0.326, 0.080 on the shiitake diet; 0.277, 0.055 on the vitamin D-2 diet and undetected, 0.494 on the vitamin D-3 diet. The transfer ratio of vitamin D (total amount of vitamin D-2 and vitamin D-3) to the egg yolk on the shiitake, vitamin D-2 and vitamin D-3 diets were 10.9%, 8.8% and 12.7%, respectively. The transfer ratio of vitamin D-3 tended to be higher than that of vitamin D-2. The content of 25-OH-D-3 in the egg yolks on the vitamin D-3 diet increased three-fold during the experimental period, and 25-OH-D-2 was detected in the egg yolk on the shiitake diet and vitamin D-2 diet. However, the content of 25-OH-D-2 in the egg yolk was significantly lower than that of 25-OH-D-3 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.