Use of Highly Purified Rations in the Study of Nicotinic Acid Deficiency.

The corn meal used in modified Goldberger diets 1 , 2 for the production of canine black-tongue provides the animals with 0.1-0.12 mg per kilo per day of nicotinic acid. 3 , 4 Dogs ingesting such diets require, in addition, approximately 0.1 mg of nicotinic acid per kilo per day. 5 This agrees with the finding 6 that adult dogs require 0.2-0.225 mg per kilo per day of nicotinic acid when fed a purified diet low in nicotinic acid. Thus half the requirement of each dog is provided by the corn meal of the Goldberger diets. Almost all dogs fed a modified Goldberger diet 1 have become acutely ill within 75 days and most of them have fallen ill within 40 days. It was thought that if dogs were fed a purified ration in which the nicotinic acid supplied was reduced to a minimum, the appearance of blacktongue should be considerably accelerated. The object was to continue the study of the physiological defects in acute deficiency rather than in intermediate stages. Eleven adult mongrel dogs were fed a purified ration whose nicotinic acid content was held almost to its minimum possible level, less than 0.01 mg per kilo per day. The diet was identical with that of Schaeffer, McKibbin and Elvehjem 7 except that corn starch was substituted for half of the sucrose component. Each dog was housed in an individual cage; food, water intake and urine were measured daily.