Evaluation of vitamin D supplements by biological assay using the turkey
Yang, H.S.; Waibel, P.E.; Brenes, J.
Journal of Nutrition 103(8): 1187-1194
1973
ISSN/ISBN: 0022-3166 PMID: 4352591 Document Number: 69321
Day-old male turkeys were given for 8 days a diet based on maize and soya bean meal without cholecalciferol. In the first trial, 26 cholecalciferol supplements were added to the diet to provide 100, 300 or 900 IU cholecalciferol/kg and when the turkeys were 24 days of age Ca, P and alkaline phosphatase were estimated in plasma, and femur ash, length, width and breaking strength were estimated. Cholecalciferol in the samples was estimated chemically by 3 industrial laboratories. In the second trial turkeys were given 8 of the samples at levels equivalent to 300 or 900 IU cholecalciferol/kg and estimations were made on day 21. Four samples had relative biological potency between 38.9 and 55.8% and 19 were above 80% by the bone ash method. Results from chemical assays did not always agree with those from biological assays and there was considerable variation between laboratories. Low levels of cholecalciferol resulted in a decrease in all values except phosphatase which increased. Femur ash, bone length and breaking strength, phosphatase and P all showed a high correlation with dietary cholecalciferol.Twenty-two samples were estimated in the third trial by the toe ash method and 5 of these were again estimated in the fourth trial. Of the 22 samples 9 had significantly lower potency than the standard and of the 5 samples 3 had a relative potency of less than 60%.