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Bureau of Dairy Industry, Agricultural Research Administration, United States Department of Agriculture
ABSTRACT
Typical deficiency symptoms (total blindness, incoordination, emaciation, and extremely low blood plasma carotene and vitamin A values) were made to appear in 12 dairy bulls at different ages by adjusting the vitamin A intake.
Seven of the animals (all that were tested more than twice) were proved fertile by artificially inseminated cows. The semen used was usually obtained in an artificial vagina but it had to be collected by massage from the animals that would not mount. These bulls were also fertile.
Generally the semen was low in concentration, had a high percentage of abnormal sperm, a high pH, and did not store well.
When gross vitamin A deficiency symptoms appeared before the expected breeding age, the bulls failed to breed; when symptoms appeared at about the expected breeding age, the bulls frequently failed to breed shortly thereafter; but when the deficiency became apparent after they had started breeding, this capacity was maintained.
At autopsy all .the bulls were found to have cystic pituitary glands. The degree of damage to the anterior lobe varied, probably less than one-fifth normal tissue remaining in four bulls, —three of which incidentally were among those proved fertile. The animals exhibiting avitaminosis A earliest in life generally showed the greatest damage to this gland.
The epithelium of the seminiferous tubules was found to have undergone degeneration—some extensively. This epithelium, the anterior lobe of the pituitary gland, and the bones of the skull were the only tissues of several examined that had become altered.
Four of the bulls were fed rations supplemented with small amounts of.carotene (8 to 11 micrograms per pound) after the appearance of avitaminosis A. This caused them to start breeding but the quality of the semen generally was not substantially improved. The testes of these animals were generally in better condition at autopsy than those of animals that did not get supplemented rations—giving evidence that carotene had brought about repair.
The germinal epithelium of one vitamin A deficient bull whose ration was supplemented but whose feed consumption was restricted was badly damaged, indicating failure to regenerate.
It is likely that gross vitamin A deficiency symptoms will appear before severe impairment to a bull's reproductive performance will occur.
1 This research was supported in part by an appropriation from Bankhead-Jones funds (Bankhead-Jones Act of June 29, 1935).
2 The authors are indebted to Mr. J. D. Hunt who assisted in certain phases of this work.
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