The Effect of Feeding a Cod-Liver Oil Concentrate to Cows on the Vitamin D Content of Milk

In an earlier paper (1) it was shown that irradiated ergosterol, when fed to cows, was an effective agent in bringing about a considerable increase in the vitamin D content of milk.At the same time it was shown that this procedure was too inefficient and too costly to warrant its adoption.The next vitamin D-containing supplement used was a cod-liver oil concentrate, known commercially as Vitex. 1 This product is prepared according to the Zucker process and contains practically no vitamin A. EXPERIMENTAL Six Holstein cows were fed a basal ration composed of second cutting, green leafy alfalfa, and the following grain mixture: 360 dried beet pulp, 200 yellow corn, 150 oats, 50 wheat bran, 50 linseed oilmeal, 4.5 salt.After the experiment had been in progress for some time the beet pulp was soaked and fed separately.Eighteen pounds of grain (including the beet pulp) and 12 pounds of hay were the allowances calculated to meet the daily requirements of the cows.This system of feeding, rather than one based on production, was followed in order to keep the food intakes of the cows equal and thus avoid any error through a greater or less intake of vitamin D in the basal ration.Towards the end of the experiment, as the cows 4ecreased in milk flow, the hay allowance was reduced to 10 pounds per cow daily.On several occasions, owing to illness, the grain allowance of individual cows had to be reduced.These periods of lowered grain intake were usually of short duration and did not influence the results, especially when it is considered that grains contain practically no vitamin D.The cows were fed and milked twice daily.The amount of milk produced at each milking was recorded and a butterfat test was made once a week on a one-day aliquot composite sample of milk from each cow.The cows were allowed to exercise for several hours each day in a vegetationfree enclosure.At the end of 17½ days of feeding on the basal ration the cows were divided into two groups of three cows each.This division was made in such