The effect on mice of practical diets containing different protein and energy levels

Mice of 2 strains were fed diets of natural ingre-dients in 3 different laboratories. The diets, which were fed before and after pelleting, contained levels of protein and energy within the ranges com-parable to those found in existing laboratory diets and were the same formulation as those fed to rats in a previous paper. The diet with the lowest energy level supported the lowest rate of bodyweight gain, as it had with rats. Little effect was noticed on food consumption, con-version efficiency or water intake. Animals fed the pelle ted diets gained bodyweight faster and there were indications of greater food and water consumption and also food conversion efficiency. It was concluded that food intake was improved with the pelleted diets resulting in the other increases. The nutritional requirements of rats and mice are usually considered as identical for practical pur-poses (Clarke et al., 1977). However, publications on the nutrition of the laboratory mouse are few compared with those for the rat and the absence of reported differences may be due to this factor rather than a true similarity between the species. Having identified some effects of diets of varying protein and energy levels in rats (Ford & Ward, 1983) similar work was conducted with mice to provide further comparative information. As in the previous study both meal and pellets were fed, as it has been suggested (Ford, 1977) that the form in which diet is presented may have a greater influence on mice than on rats. In this study both forms of diet were fed during the same experiment to allow closer comparison. Materials & methods Diets The 5 diets used were those described for rats (Ford & Ward, 1983). They were fed either in meal form or following pelleting