Sterilization of laboratory animal diets using gamma radiation

Abstract

Sterilization by gamma radiation has proved to be a suitable method for the treatment of a variety of laboratory animal diets intended for specified-pathogen-free (SPF) and germ-free colonies. Due to the high penetrating power of this radiation the diets can be packed before treatment in a manner which prevents recontamination during transport and storage. The main bulk of diets is used for SPF animals and a radiation dose of 2.5 Mrad has proved effective for the control of contaminating organisms. No adverse effects on animals receiving the diets have been noted, observations having been made on growth, reproduction and general health. Irradiated diets formulated according to current laboratory animal practice appear to be nutritionally satisfactory.

The Experimental Induction of Leukoencephalomyelopathy in Cats

“…Low doses of up to 1 kGy are used to delay the ripening of fresh foodstuffs, whereas medium doses of up to 10 kGy prolong the shelf life of food. 40 At doses greater than 10 kGy, this technology has been widely used to sterilize diets for SPF and germ-free animals, 25,42,46 although such treatment can reduce the diet's vitamin content. 8,13,25,39,40,42 In pure solution the B vitamin thiamine (B 1 ) is the most sensitive to the effects of radiation followed by vitamin C, pyridoxine (B 6 ), riboflavin (B 2 ), and niacin.…”

“…40 At doses greater than 10 kGy, this technology has been widely used to sterilize diets for SPF and germ-free animals, 25,42,46 although such treatment can reduce the diet's vitamin content. 8,13,25,39,40,42 In pure solution the B vitamin thiamine (B 1 ) is the most sensitive to the effects of radiation followed by vitamin C, pyridoxine (B 6 ), riboflavin (B 2 ), and niacin. Vitamin E is the most radiosensitive of the fat-soluble vitamins, followed by vitamins A and K. However, these sensitivities vary significantly when vitamins are incorporated within food products.…”

Sterilization by Gamma Irradiation

“…The results indicate no significant effect of irradiation on protein quality. Amino acid composition was similarly very little affected (Ley, 1969). By comparison of the different treatments (different radiation doses) and the control sample (not irradiated) of bean, it was observed that there was no significant alteration in the amino acid contents up to the maximum dose of 10 kGy.…”

“…In addition, studies at higher levels of irradiation have demonstrated the destruction of vitamins A and K in food (Stevinson et al, 1959). The question of vitamin K in irradiated diets requires special considerations: i. it is known to be susceptible to destruction by y-irradiation (Ley, 1969); ii. it is synthesized by microbial action in the gut, and animals (particularly those that practice coprophagy) can satisfy part of their requirement by this means.…”

A comparison between irradiated and autoclaved diets for breeding mice, with observations on palatability

“…showed that the most satisfactory non-sterile commercially produced diet when sterilized either by gamma irradiation or by autoclaving at 15 Ib/in 2 (10500 kg/m 2) for 30 min maintained normal growth, reproduction and lactation in inbred and non-inbred mice. Ley, Bleby, Coates & Paterson (1969) reported that irradiated diets formulated to current laboratory animal practice appeared to be nutritionally satisfactory.…”