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Effects of Cholecalciferol Steroids on Bone and Egg Shell Calcification in Japanese Quail¹

Poultry Science Department, University of Maryland, College Park, Maryland 20742

The effect of various forms and dietary levels of cholecalciferol (CC) on the calcification of egg shells and bone tissue was investigated in three experiments using mature Japanese quail hens. The birds were initially 26 to 28 weeks of age, with the experimental diets administered over a 6 week period. The biological activity of the CC metabolite, 25-hydroxycholecalciferol (25-OH-CC) was approximately 1.5 times CC, regardless of dietary level or parameter measured. In general, 1 -hydroxycholecalciferol (1 -OH-CC) was shown to be very effective, particularly at dietary levels below the NRC requirement, where activity estimates ranged from 5.3 (based on egg shell breaking strength) to 9.5 (egg shell thickness) times that of CC. At the requirement level, the activity estimates for 1 -OH-CC were approximately 2.5 times that of stock CC. A consistent, but non-significant advantage over cholecalciferol was observed with almost every parameter measured when 1 -OH-CC or 1 , 25-dihydroxycholecalciferol (1,25-(OH)₂CC) was fed at the 5.0 µg/kg level. This may indicate a diminished capacity of the kidney in the aging quail hen to hydroxylate the number one position of the 25-OH-CC molecule. In addition, these results appear to suggest potential applications for 1 -OH-CC in the treatment of age-related bone and egg shell fragility in animals.

KEY WORDS: • cholecalciferol • vitamin D • calcification • quail

¹ Scientific Article No. A2513, Contribution No. 5545 of the Maryland Agricultural Experiment Station.

² Send all reprint requests to Dr. Joseph H. Soares, Jr., Associate Professor, Department of Poultry Science, University of Maryland, College Park, Maryland 20742.

Manuscript received 17 October 1978.