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Calcium Assimilation as Indicated by Bone Analysis in Long-Time Experiments

Bureau of Dairy Industry, U. S. Department of Agriculture, Washington, D. C.

ABSTRACT

Four cows were maintained under herd conditions on a ration of timothy hay, a grain mixture, and corn silage for periods of fourteen to thirty-two months.

Analyses were carried out on the bones of one of these cows (thirty months on timothy) and on those of two other animals which had been on alfalfa hay for some time before slaughter. Calculations have been made of the percentages of calcium assimilated by the four cows on timothy hay.

1. The results indicate that the relative amounts of ash, calcium, phosphorus, nitrogen, and organic matter in cows' bones are little if at all altered by long periods on rations low in calcium, even when a considerable amount of milk is given in such periods.
   
2. The results suggest that the treatment above described reduces by from 10 to 20 per cent the total weight of the bones, and, therefore, the amounts of calcium and phosphorus in the body.
   
3. The results indicate that, even on a mediocre roughage, the calcium assimilation tends to be somewhat higher in long periods under natural conditions than it has been in most balance experiments, and that, in the case of good cows, it may be much higher than it has been in most balance experiments.