Therefore,during the anestrous period heifers or cows cannot becomepregnant. Standing Estrus and Ovulation Standing estrus, also referred to as standing heat, is the most visualsign of each estrous cycle. It is the period of time when a female is sex-ually receptive. Estrus in cattle usually lasts about 15 hours but can range from less than 6hours to close to 24 hours. In cattle, the period of time when a female will standand allow mounting by other animals (Fig 1) is the sexually receptive period.