Abstract
Widely differing ranges for the preferred first-mating age for rats have been reported by different investigators. As well as being of physiological interest this information is important for optimum utilization of animal resources. Previously published results, however, do not provide sufficient information on mortality and the numbers of pups born and weaned. We studied 1623 pups born to 36 female Wistar rats. Dams were first mated at the age of 35 days or 70 days or 105 days. The results show that reproduction and weaning weights increase with an increased first-mating age of dams, although the pup mortality rate also increases. This study can be used when a programme for the production and supply of Wistar rats is planned.