Vitamin A Deficiency in Cattle Under Natural Conditions. ∗

Abstract

On California ranges during the dry feed season, conditions are favorable for the development of vitamin A deficiency in livestock. Under average conditions, however, the length of the dry season coupled with the varied sources of feed containing some vitamin A is such that the reserves accumulated in the bodies of the animals from the green feed season are sufficient to carry them through the drought period. While its existence has been suspected during recent years, the past winter has been the first time the diagnosis has been definitely established. This was possible because weather conditions and management of one ranch in southern Tulare County caused its development in such a severe form that 100 animals died with many more showing symptoms in a herd of about 250 head.

The ranch comprises 3000 acres of land practically all of which is farmed to wheat and barley. The owner maintains 75 dairy cows. Calves from these cows, together with others purchased when a few days old from dairy farmers, nurse these animals. The calves are finally sold for veal.

In the spring of 1932 rains ceased early, resulting in the feed being dry and grain fields yellow by May 15. In the fall the first rains came about the middle of December and were followed by such cold weather that green feed did not become available until the middle of February, 1933.

During this unusually long dry feed period, of 9 months, part of the cattle grazed the unharvested grain fields through the summer. Thirty-five of the cows were left on a leased adjoining natural range until August 10th and then placed on stubble from which wheat and barley had been harvested. Early in the fall and through the winter they were fed roughage from a stack adjoining the corral.