Abstract
An excessive supply of vitamin D2-fortified shiitake mushroom was continued for a long period in laying hens to examine the stability of producing vitamin D-fortified eggs and safety to the hens. Vitamin D2-fortified shiitake mushroom containing 80μg/g vitamin D2 was added to diets at 0, 0.25, 0.5, 1.25 and 5% levels, respectively, and were fed to White Leghorn for 30 weeks. The content of vitamin D2 in the egg yolk increased until the 6th or 8th week and then reached a plateau. Laying hens constantly produced vitamin D-fortified eggs for 30 weeks. The content of vitamin Din the egg yolk was proportional to the level of fortified shiitake mushroom added. Vitamin D content of the egg yolk on the 5% diet was 62μg/g, 125 times higher than that on the control diet. The content of 25 (OH) D2 in the egg yolk showed the similar trend to that of the vitamin D content in the egg yolk, and increased proportionally to the levels of vitamin D2-fortified shiitake added. This experiment suggested that 25 (OH) D2 could be easily obtained from eggs. Vitamin D and 25 (OH) D2 also seemed to be accumulated in chicken liver and meat. Comparing the amounts of vitamin D in various tissues of hens, leg muscle rich in fat contained 0.38 μg/g, which was 5 to 6 times higher than that of the breast muscle and pectoral muscle. An excessive supply of vitamin D2-fortified shiitake mushroom did not affect the performance of laying hens, egg shell quality and concentrations of calcium and phosphorus in the serum. The health status of laying hens was good as well except for an inflammatory kidney on the 5% diet.
