The effects of nutrition on the length of the postpartum interval (PPI, the interval from parturition to the first postpartum estrus that is accompanied by ovulation) were reviewed for the ewe, sow and cow. Unfortunately, information on the effects of nutrition on the PPI of the mare is nonexistent. Absence of estrus following weaning is a problem in postpartum sows, especially during the summer. High feed intake (more than 3 kg daily) immediately after weaning decreases the incidence of anestrus in sows of some breeds, but not in others. The incidence of prolonged intervals between weaning and estrus and the incidence of anestrus is more frequent in primiparous than in multiparous sows. The effect of nutrition on the PPI of the ewe is more controversial than that for the sow. In mature Merino ewes, neither lactation nor undernutrition during lactation affects the duration of the PPI while both factors increase the length of the PPI in coarse-wool breeds. Undernutrition during lactation increases the incidence of anestrus in primiparous fall-lambing Merino ewes. A cow must conceive by 80 days postpartum to have a 365-day calving interval. Excessive length of the PPI in dairy cows does not appear to be one of the major detriments to fertility since most dairy cows have a PPI of considerably less than 80 days. While feeding high protein diets to high-producing dairy cows shortens the PPI; this practice also increases the interval from parturition to conception. Weight changes, both before and after calving, and body condition at calving interact to affect the PPI of suckled beef cows. The length of the PPI in cows that are in good body condition at calving is not affected by either pre- or postpartum weight changes. More cows in moderate and thin body condition showed estrus by 60 days postpartum if the cows had gained weight prior to calving compared with those that lost weight prior to calving. A high percentage of thin cows that lose weight prior to calving does not show estrus following calving unless they gain weight after calving. The length of the PPI is affected by many factors, for example: parity, breed, lactation, environment and endocrine status. Designs of future experiments must be cognizant of these factors and the possible interactions of these factors with the nutritional status of the animal.