Relationship Between Carotene, Blindness Due to Constriction of the Optic Nerve, Papillary Edema and Nyctalopia in Calves

Abstract

Calves fed low carotene rations develop nyctalopia, papillary edema and a permanent type of blindness associated with a constriction of the optic nerve. The development of these conditions can be prevented by supplementing the low carotene ration with crystalline carotene dissolved in cottonseed oil. Consequently these conditions appear to be a part of the syndrome of vitamin A deficiency in calves. The development of the constriction of the optic nerve is associated with a stenosis of the optic canal, papillary edema and probably increased intracranial pressure. The development of papillary edema and nyctalopia are separate processes but both are due to vitamin A deficiency. Vitamin A deficiency in calves is usually not associated with the development of keratitis. Vitamin A deficiency in calves is associated with a condition of syncope, most likely produced by increased intracranial pressure. Vitamin A deficiency in calves may be diagnosed by the presence of both papillary edema and nyctalopia. Papillary edema persists for a considerable period after feeding carotene. Under proper conditions of observation bleaching of the tapetum lucidum of the retina is a good guide for the diagnosis of vitamin A deficiency in the bovine. Plasma carotene determinations of the bovine also give an indication of the vitamin A reserve where the colorless vitamin A is not being fed and the carotene intake is somewhat limited.