Abstract
A system for breeding from obese male mice (ob/ob) by restricting food intake is described. It is shown that a 40% reduction in food intake at 6½-8½ weeks of age is optimal in the colony under review. Males on restricted diet did not mate immediately but went through a period of adaptation; the mean time before vaginal plugs were observed was 30 days. Subsequent vaginal plugs occurred on average every 17 days and 69% of these matings resulted in litters. Under optimal conditions over 90% of all obese males set up on restricted diets mated and sired young.