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Assessing Adequacy of Cholecalciferol Supplementation in Chicks Using Plasma Cholecalciferol Metabolite Concentrations as an Indicator^1,2,

U.S. Department of Agriculture, Agricultural Research Service, National Animal Disease Center, Metabolic Diseases and Immunology Unit, Ames, IA 50010-0070

Cholecalciferol (vitamin D) deficiency rickets remains an occasional problem in poultry. Diagnosis currently relies on analysis of feed and histopathological examination of bone. These experiments were designed to provide data that might allow diagnosis of cholecalciferol deficiency on the basis of plasma concentrations of 25-hydroxycholecalciferol, a circulating metabolite of cholecalciferol. Day-old broiler chicks were fed corn-soybean meal or purified ingredient cholecalciferol-deficient diets supplemented with 0, 5, 10, 15, 20, 25, 37.5 or 75 µg cholecalciferol/kg diet. Plasma and bone samples were collected 21 d later. Chicks fed the unsupplemented purified ingredient diet became truly deficient, having no detectable plasma concentrations of the cholecalciferol metabolites 25-hydroxycholecalciferol, 1,25-dihydroxycholecalciferol, or 24,25-dihydroxycholecalciferol. Chicks fed the corn-soybean meal diet without supplementation had low but detectable concentrations of both 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol in plasma. Body weight, bone calcium and bone phosphorus concentrations of chicks fed the corn-soybean meal diet suggest that the cholecalciferol requirement of broiler chicks is at least 10 µg/kg diet. At this dietary level of cholecalciferol, plasma 25-dihydroxycholecalciferol concentration was 12.5 nmol/L. One hundred percent of the theoretical maximal response in body weight and bone calcium content was seen at 20 µg cholecalciferol/kg diet, which increased plasma 25-hydroxycholecalciferol concentration to 25 nmol/L in the chicks fed the corn-soybean meal diet. These data provide a nomogram of plasma 25-dihydroxycholecaiciferol concentration that can be expected from including different concentrations of cholecalciferol in the diet, and also offer a means of diagnosing cholecalciferol deficiency in field cases of rickets.

KEY WORDS: • vitamin D • chicks • bone • 1,25-dihydroxycholecalciferol • cholecalciferol

¹ Names of products are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable.

² The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.

³ To whom correspondence should be addressed.

Manuscript received 26 April 1994. Revision accepted 3 November 1994.

This article has been cited by other articles:

				S. V. R. Rao, M. V. L. N. Raju, A. K. Panda, G. S. Sunder, and R. P. Sharma Effect of High Concentrations of Cholecalciferol on Growth, Bone Mineralization, and Mineral Retention in Broiler Chicks Fed Suboptimal Concentrations of Calcium and Nonphytate Phosphorus J. Appl. Poult. Res., January 1, 2006; 15(4): 493 - 501. [Abstract] [Full Text] [PDF]