동물사료의 위생적 관리를 위한 효과적인 살균방법에 관한 비교 연구

Distribution of microorganisms in animal feeds and their effect of gamma-irradiation on disinfection and storage of mixed feeds

In this study we investigated the distribution of microorganisms in feed ingredients and mixed feeds, and effect of radiation-inactivation of the microorganisms. The contamination of animal feeds was remarkable, and the number of total counts in feed ingredients and mixed feeds in mash for chick and other kind of animals were 2.7×10³ to 3.0×10⁴ and 5.3×10⁴ to 2.2×10⁶ per gram, respectively. The coliforms were counted from 5.2 to 5.8×10³ and 5.1×10³ to 6.8×10⁵ per gram. Other kinds of fungi were 5.0×10² to 1.7×10³ and 2.1×10³ to 4.5×10⁵, respectively. In the case of mixed feeds in pellet, total counts were 5.3×10³ to 1.0×10⁶, coliforms were 0 to 1.6×10³, molds were 0 to 1.6×10³ per gram. The contamination of fish meals was not remarkable, and only the mixed fish meal was contaminated largely with fecal coliforms and other microorganisms. In this respect, it seems to be necessary to prevent the damages of feedstuff caused by growth of molds and insects, and to eliminate pathogens. Osmophilic molds were radiation-sensitive and eliminated below identification limit by 2 kGy irradiation, Coliforms were more radiation-resistant and they were eliminated by 5 to 8 kGy. From these results, it could be said that the irradiation at 5 kGy is enough to reduce the total counts below 10³ per gram and to eliminate fecal coliforms from mixed feeds, and the dose of more than 2 kGy is necessary to prevent the mold growth during storage. Before and after gamma-irradiation at doses ranging from 5 to 30 kGy, practical type diets for chicks were assayed for their chemical composition. Irradiation had little effect on crude protein, crude ash and moisture, while 10 to 15 percent of crude fat was lost. The results of feeding study with chicks indicated that the irradiation of diet did not produce any significant disorders in growth and feed conversion for three weeks. But in body weight changes, the chicks fed with autoclaved diet were significantly decreased than chicks fed with the others.