The Influence of Casein Levels in Semisynthetic Diets on the Growth and Reproduction of Common Voles (Microtus Arvalis Pallas)

The growth and reproduction rates of young male and female voles (Microtus arvalis Pallas) were compared by feeding the animals 5, 10, 15, and 20% casein compound diets, respectively, which were prepared to contain approximately equal calories. There was little difference in growth rates among the animals that were fed compound diets containing 20, 15, and 10% casein respectively. However, the growth rates of animals fed the compound diet containing 5% casein were retarded. The concentration of fermentation products in the forestomach and caecum were lower in animal groups fed the test compound diets than in animals fed a control diet (hay-cube and pellets for herbivores). The animals which were fed the 5% casein compound diet had lower plasma protein concentration and hematocrit values, as compared to animals which were fed the other casein compound diets. A greater reproduction rate was observed in the animal group which was fed the 20% casein compound diet than in the animal groups which were fed the 15% and 10% casein compound diets. The animals which were fed the 5% casein compound diet failed to reproduce. As the result, it is considered that voles need the 20% casein-protein diet for normal reproduction, although the 10% casein-protein diet appears sufficient for the growth of the animal.