Stability of Nutritional and Sterility Properties of Irradiated and Autoclaved Diets and Their Effect on the Sprague–Dawley Rat

Abstract

Cobalt-60 gamma radiation has been used as an alternative method to sterilize laboratory animal diet for specific pathogenfree colonies at our institution since 2008. The purpose of this study was to compare shelf life in terms of nutritional and sterility properties of irradiated and autoclaved diets with their effect on 20 mate pairs of Sprague–Dawley rat. Validated gamma irradiation dose and autoclaved temperature that could be used to completely sterilize entire batches were 15 to 20 kGy and 121 °C for 15 min, respectively. The stability of crude protein, fat, calcium, phosphorus, and vitamin E of both diets was preserved for 6 mo. Autoclaved sterilization process led to significantly reduced vitamin A (nonautoclaved; 22.10 ± 0.65, 0 mo; 9.56 ± 0.21, 3 mo; 9.36 ± 0.42, 6 mo; 16.50 ± 0.77 IU/g; P < 0.01), vitamin B1 (nonautoclaved; 0.96 ± 0.15, 0 mo; 1.11 ± 0.08, 3 mo; 0.39 ± 0.02, 6 mo; 0.57 ± 0.02 mg/100g; P <0.01), and vitamin B2 (nonautoclaved; 2.43 ± 0.54, 0 mo; 0.67 ± 0.01, 3 mo; 1.17 ± 0.18, 6 mo; 1.81 ± 0.02 mg/100g; P < 0.01); moreover, their stability were not preserved at 3 mo. In contrast to this, the irradiated diet’s stability was preserved for 6 mo. This might be explained by the high temperature of steam and the increase in the humidity percentage in the autoclaved diet 699 Abstracts of scientific papers 2010 AALAS National Meeting (nonautoclaved; 7.02 ± 0.03, 0 mo; 8.15 ± 0.02, 3 mo; 8.09 ± 0.08, 6 mo; 8.89 ± 0.13%; P < 0.01) since increased water content has been shown to accelerate vitamin destruction but the stability of amino acids or protein quality seems unaffected. The sterility property of both diets was preserved for 6 mo. All related parameters reflected in animal health, consumption rate (16.55 ± 0.99, 16.65 ± 0.96 g/d), fertility (82.50 ± 1.44, 81.25 ± 1.72%), wean (98.87 ± 0.87, 100.00 ± 0.00%), production (81.45 ± 1.25, 81.25 ± 1.72%), litter size (10.32 ± 0.21, 10.60 ± 0.48%), clinical, hematological, and histologic of several organs, in both diets were preserved. The study revealed that the nutritional value tended to be reduced, particularly of vitamin A, B1, and B2, in autoclaved sterilization process. There were no adverse effects of either diet on the animals. The expected shelf life of irradiated and autoclaved diets is 3 and 1 mo, respectively