Effect of Gamma Irradiation on Microbial Decontamination, Crude Nutrient Content, and Mineral Nutrient Composition of Laboratory Animal Diets

Document Type: Original Articles


1 Nuclear Agriculture Research School, Nuclear Science and Technology Research Institute, Karaj, Iran

2 Department of Molecular Medicine, Faculty of Advanced Medical Sciences, Tabriz University of Medical Sciences, Tabriz, Iran

3 Cancer Biology Research Center, Tehran University of Medical Sciences, Tehran, Iran

4 Department of Research, Breeding and Production of Laboratory Animals, Razi Vaccine and Serum Research Institute, Agricultural Research, Education and Extension Organization, Karaj, Iran


Laboratory animal models are an important part of test design. Certain conditions such as microbial contamination in diets of these models could affect the results of experiments. One of the most important routes that predispose to contamination is generated through feeding of laboratory animals. This study aimed to show the effect of gamma irradiation in reducing bacteria concentrations, crude nutrient content, and concentrations of some minerals and trace elements in laboratory animal diets. Large-sized pellets with 10–15 mm diameter (commonly used for rats and hamsters) and small-sized pellets with 3–5 mm diameter (used for rabbits and guinea pigs) along with skimmed milk powder (SMP) as a food additive were exposed to gamma irradiation with different doses ranging from 3 to 30 kGy. The total microbial contamination and any possible changes in some mineral nutrient composition and the crude nutrient content were determined pre- and post-irradiation. Our data revealed that 25 kGy in pelleted diets and 18 kGy in SKM had superior effects in the reduction of bacterial contamination with little change in crude nutrient content and minerals and trace elements in nutrient requirements of laboratory animals. According to the results, gamma irradiation had minimal effects on crude nutrient content and the concentrations of some minerals and trace elements of laboratory animal diets, and it also eliminated bacterial and fungal contamination load. By using gamma irradiation, this method could yield a favorable outcome in controlling microbial contamination of animal diets.


Main Subjects

Article Title [French]

Effet de l'irradiation Gamma sur la Décontamination Microbienne, la Teneur en Éléments Nutritifs Bruts et la Composition en Éléments Minéraux des Régimes Alimentaires des Animaux de Laboratoire

Abstract [French]

Les modèles d'animaux de laboratoire jouent un rôle important dans la conception des tests. Certaines conditions telles que la contamination microbienne des régimes alimentaires de ces modèles pourrait affecter les résultats des expériences. L’alimentation des animaux de laboratoire est l’une des voies de contamination les plus importantes. Cette étude visait à montrer l’effet de l’irradiation gamma sur la réduction des concentrations de bactéries, teneur en éléments nutritifs et concentrations de certains minéraux et oligo-éléments dans les régimes alimentaires des animaux de laboratoire. Des granulés de grande et petite taille d’un diamètre respectif de 10–15 mm (couramment utilisés chez le rat et le hamster) et des de 3–5 mm (utilisés pour les lapins et les cobayes) contenant du lait en poudre écrémé (lait écrémé en poudre) comme additif alimentaire, ont été exposés à une irradiation gamma à des doses allant de 3 à 30 kGy. La contamination microbienne totale et tout changement éventuel de la composition de certains éléments minéraux nutritifs et la teneur en éléments nutritifs bruts a été déterminée avant et après irradiation. Nos données ont révélé que 25 kGy en granulés et 18 kGy dans SKM ont eu des effets supérieurs dans la réduction de la contamination bactérienne avec peu de changement de la teneur en éléments nutritifs bruts, des minéraux et des oligo-éléments constituant les besoins en éléments nutritifs des animaux de laboratoire. Selon nos résultats, l’irradiation gamma a eu des effets minimes sur le contenu en nutriments bruts et sur la concentration de certains minéraux et oligo-éléments des aliments et a permis d‘éliminer la charge de contamination bactérienne et fongique. En utilisant l'irradiation gamma, cette méthode pourrait aboutir à un résultat favorable dans le contrôle de la contamination microbienne des régimes alimentaires des animaux.

Keywords [French]

  • Irradiation gamma
  • Animal de laboratoire
  • Régime alimentaire
  • Bactéries
  • Granulés
(APHIS), 2017. U.S. Department of Agriculture's Animal and Plant Health Inspection Service Annual Report Animal Usage by Fiscal Year.

Adamiker, D., 1975. A comparison of various methods for treating feedstuffs for laboratory animals. Food Irrad Info 5, 19-42.

Adamiker, D., 1976. Irradiation of laboratory animal diets. A review. Z Versuchstierkd 18, 191-201.

Al-Masri, M.R., Zarkawi, M., 1994. Effects of gamma irradiation on chemical compositions of some agricultural residues. Radiat Phys Chem 43, 257-260.

Analytical-Methods-Committee, 2000. Determination of thiamine and riboflavin in pet foods and animal feedingstuffs. Analyst 125, 353-360.

Arvanitoyannis, I.S., Stratakos, A.C., 2010. Potential Uses of Irradiation. Irradiation of Food Commodities, Academic Press, Boston, pp. 635-669.

Caulfield, C.D., Cassidy, J.P., Kelly, J.P., 2008. Effects of gamma irradiation and pasteurization on the nutritive composition of commercially available animal diets. J Am Assoc Lab Anim Sci 47, 61-66.

Chiang, Y.-C., Huang, G.-J., Ho, Y.-L., Hsieh, P.-C., Chung, H.-P., Chou, F.-I., et al., 2010. Influence of gamma irradiation on microbial load and antioxidative characteristics of Polygoni Multiflori Radix. Process Biochem 46, 777-782.

Clarke, H.E., Coates, M.E., Eva, J.K., Ford, D.J., Milner, C.K., O'Donoghue, P.N., et al., 1977. Dietary standards for laboratory animals: report of the Laboratory Animals Centre Diets Advisory Committee. Lab Anim 11, 1-28.

Cowie, R.A., Makkar, H.P., 2013. Quality assurance for microbiology in feed analysis laboratories, FAO.

DeRouchey, J.M., Tokach, M.D., Nelssen, J.L., Goodband, R.D., Dritz, S.S., Woodworth, J.C., et al., 2003. Effect of irradiation of individual feed ingredients and the complete diet on nursery pig performance. J Anim Sci 81, 1799-1805.

DeRouchey, J.M., Tokach, M.D., Nelssen, J.L., Goodband, R.D., Dritz, S.S., Woodworth, J.C., et al., 2004. Evaluation of methods to reduce bacteria concentrations in spray-dried animal plasma and its effects on nursery pig performance. J Anim Sci 82, 250-261.

Fox, J.G., Barthold, S., Davisson, M., Newcomer, C.E., Quimby, F.W., Smith, A., 2006. The mouse in biomedical research, Academic Pr.

Furuta, M., Suwa, T., Kuwabara, Y., Otsuhata, K., Takeda, A., 2002. Electron-beam sterilization of laboratory animal diets--sterilizing effect of 10-MeV electrons from a linear accelerator. Exp Anim 51, 327-334.

Groesbeck, C.N., Derouchey, J.M., Tokach, M.D., Goodband, R.D., Dritz, S.S., Nelssen, J.L., 2009. Effects of irradiation of feed ingredients added to meal or pelleted diets on growth performance of weanling pigs. J Anim Sci 87, 3997-4002.

Hagiwara, A., Yoshino, H., Sano, M., Kawabe, M., Tamano, S., Sakaue, K., et al., 2005. Thirteen-week feeding study of thaumatin (a natural proteinaceous sweetener), sterilized by electron beam irradiation, in Sprague-Dawley rats. Food Chem Toxicol 43, 1297-1302.

Halls, N.A., Tallentire, A., 1978. Effects of processing and gamma irradiation on the microbiological contaminants of a laboratory animal diet. Lab Anim 12, 5-10.

Jorgensen, J.H., Ferraro, M.J., 2009. Antimicrobial susceptibility testing: a review of general principles and contemporary practices. Clin Infect Dis 49, 1749-1755.

Lee, J.-Y., Cho, S.-B., Kim, Y.-Y., Ohh, S.-J., 2010. Effect of gamma irradiation on nutrient digestibility in SPF mini-pig. Radiat Phys Chem 80, 123-124.

Morehouse, K.M., Komolprasert, V., 2004. Irradiation of food and packaging: an overview. ACS Publications.

National Research Council. Subcommittee on Laboratory Animal, N., 1995. Nutrient requirements of laboratory animals, National Academies Press.

Short, D.J., 1968. Animal Care Program of the Medical Research Council of Great Britain. Can Med Assoc J 98, 893-896.

Simas, M.M.S., Albuquerque, R., Oliveira, C.A., Rottinghaus, G.E., Correa, B., 2010. Influence of gamma radiation on productivity parameters of chicken fed mycotoxin-contaminated corn. Appl Radiat Isotopes 68, 1903-1908.

Wescott, R.B., Gardner, J.A., 1962. Apparatus and methods for the steam sterilization of feed for germfree laboratory animals. Technical manuscript 7.