Novel Metabolism of Vitamin D in Poultry: Prevention of the Leg Weakness and Eggshell Broken

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A large amount of economic loss is produced by several disorders related with calcium metabolism, the leg weakness and eggshell thinning, in the poultry industry. These disorders have been considered as a consequence of the disruption of vitamin D metabolism. In general, the biologically active form (1a,25-(OH)2D3) is converted from vitamin D3 via a two-step hydroxylation process catalyzed by 25-hydroxylase in the liver and 1a-hydroxylase in the kidney.In this research project, the mRNA expression of 1a-hydroxylase was indicated in the extra-renal vitamin D-target tissues such as intestines and eggshell gland. The expression was also stimulated by estrogen, and inhibited with aging. These results suggested that 1a,25-(OH)2D3 is locally synthesized from 25-hydroxycholecalciferol (25-(OH)D3) in target-tissues, and directly regulates calcium metabolism. Here, we furthermore suggested that 25-(OH)D3 supplement improves eggshell quality by modification of local vitamin D metabolism.