Toxic Effects produced by Pyrimethamine in Chickens and their Antagonism by Folic Acid

Abstract

PYRIMETHAMINE, a folic acid antagonist, has been shown to potentiate the activity of sulphadimidine and sulphaquinoxaline against cæcal coccidiosis in chickens (ref. 1 and Ball, S. J., private communication). During our investigation of this combination, the decreased growth-rate and anæmia observed in Rhode Island × Light Sussex chickens fed for 28 days on an all-mash diet containing 20 p.p.m. of pyrimethamine, appeared to be controlled by a dose of 10 mgm./kgm. folic acid. The mean weight gain over the experimental period is shown in Table 1. Daily erythrocyte counts were made in blood taken from the wing vein (Fig. 1). After 21 days the erythrocyte count, hæmatocrit and hæmoglobin concentration in the heart blood and the total liver iron content of each of the birds were measured (Table 1). Sections of liver, treated with potassium ferrocyanide, were examined for hæmosiderosis.