A metabolic study was conducted for 3-day, after a 4-week period of feeding trial and assessment of different diets for bioavailability of different nutrients conducted on 25 weanling albino rats divided into 5 experimental groups. The diets contained calcium and protein of varying (animal and plant) sources. Absorption of diet was the maximum (95.07 to 95.82%) in rats fed 10% casein or egg protein and the lowest (86.88%) in vegetable protein (ragi:wheat:bengalgram mixture) during the 3-day metabolic trial. Retention of calcium was the maximum in the case of egg protein (69.22 mg) and the lowest in vegetable protein (51.53 mg). Similarly, calcium absorption was maximum in the case of egg protein diet and very low in the vegetable protein diet. Phosphorus balance. showed exactly opposite trends. Phosphorus retention was the highest in the vegetable protein diet (66.90 mg) and the lowest in the casein protein diet (15.85 to 26.68 mg). Although the per cent absorption was practically the same in vegetable and casein protein (87.95 to 88.79%), but highest in egg protein (93.08%). It is concluded that the calcium bie-availability is the best from egg protein compared to casein and vegetable protein. So far as calcium source is concerned, there was no difference in available calcium from oyster shell and egg shell powder compared to salt mixture used in the experiment.