Meadow Vole Nutrition Studies with Semisynthetic Diets

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Abstract
Weanling voles were fed 55 diets which varied from 3 to 26% casein, 14 to 73% carbohydrate, and 0 to 76% cellulose fiber. Multiple regression equations were calculated to predict vole weight gain (R2 = 0.86), intake (R2 = 0.80), apparent digestibility (R2 = 0.97) of dry matter, caloric and nutrient utilization (R2 = 0.77 to 0.86) from dietary composition. With voles the use of dietary composition gave greater predictability than did daily nutrient intake. Response contours are presented on a portion of an equilateral triangular pattern, the sides of which represent the three dietary components. This facilitated the interpretation of the effects of various combinations of casein, carbohydrate and fiber. Weanlings made rapid intake adjustments to both casein and carbohydrate dietary levels while gaining weight at all but extreme dietary component combinations. Predicted daily gain reached a maximum of more than 0.9 g/day when diets contained 11 to 24% casein, 28 to 51% carbohydrate, and 25 to 53% fiber. These responses of voles to protein and energy levels suggest the desirable nature of this animal for several assay purposes. The beneficial effects of intermediate levels of dietary fiber on weight gain and nutrient utilization were probably due to phenomena other than energy supply.