THE EFFECTS OF CHRONIC TANNIC-ACID INTAKE ON PRAIRIE VOLE (MICROTUS-OCHROGASTER) REPRODUCTION

The hypothesis was tested that the reproductive performance of voles w ould be reduced when fed diets containing tannins either because of in creased metabolic rates, decreased intake, or decreased digestive effi ciency. We fed a ration containing 4% tannic acid (TA) (dry mass basis ) to 24 pair of prairie voles (Microtus ochrogaster) and compared repr oductive performance (litter size, birth weights, body mass of the you ng until weaning, and mass changes in the dams) to that of 24 pair of prairie vole fed a control ration. We also compared the intake rates, digestive efficiency, and metabolic rates [as measured by Vo2 consumpt ion (cm3/hr)] of dams and young fed both rations. Voles consuming 4% T A diets produced litters of similar size and mass as did voles fed the control ration. Furthermore, the mass of the young of dams fed the ta nnic acid ration were similar to the young of dams consuming the contr ol ration through day 19 postpartum. However, dams consuming the tanni c acid ration lost mass throughout lactation while the control dams ma intained mass. Because the Vo2 rates of both treated and control dams and litters were similar, we conclude increased metabolic costs were n ot the reason for the observed mass loss but, rather, reduced digestiv e efficiency, reduced intake of digestible dry mass, and apparent dige stible nitrogen.