Effects of gamma-irradiation on the vitamin content of diets for laboratory animals

Abstract

Practical-type diets for chicks, guinea-pigs and cats, and a chick diet of purified ingredients, were assayed for their vitamin content before and after gamma-irradiation at doses ranging from 2 to 5 Mrad. Irradiation of guinea-pig and chick diets resulted in small losses of vitamin A (in this investigation, 6 and 12 per cent respectively). Losses of vitamin E were larger (24 and 65 per cent) but were much less (11 per cent) when the diets were vacuum-packed before irradiation. Vitamins were less stable in the purified chick diets, the most susceptible being vitamins A, E, B₆ and thiamine. Vitamin destruction was greatly increased when antioxidants were incorporated into this diet, and also when its moisture content was high. Vitamin A and β-carotene were almost completely destroyed in the cat diet, where there was also some loss of thiamine and folic acid.