The postpartum buffalo. II. Acyclicity and anestrus.
Prolonged postpartum acyclicity (absence of ovarian cyclic activity) and anestrum (absence of overt estrous signs) are major sources of economic loss to buffalo breeders. Studies on the epidemiology of these two problems are highly recommended to achieve successful control. Review of the available literature on controlled studies in dairy buffaloes revealed that first ovulation as detected by rectal palpation and progesterone analysis occurred between 28-71 and 24-55 days, respectively, after calving. Postpartum estrus in the same studies occurred between 44 and 87 days. Reports concerned with data compiled from breeding records of research stations, breeding farms and small holders where estrus is a subjective measure, gave much longer periods. Also data from Egypt, India and Pakistan indicate that only 34-49% of buffaloes showed estrus during the first 90 days after calving and 31-42% remained anestrus for more than 150 days. In swamp buffaloes both postpartum ovulation and estrus are more delayed than in dairy buffaloes. The role of suckling, nutrition, body condition score at calving, milk yield, parity, season of calving and other minor factors were discussed. First postpartum ovulation is frequently followed by one or more short estrous cycles (<18 days). Long anovulatory and anestrous periods due to prolonged inter-luteal phase were reported to occur after short cycles. Also long anestrous periods due to cessation of cyclic activity (true anestrus) for 3 or more weeks and prolonged luteal activity for 28 days or more were described to occur in about 25 and 8-11% of the buffaloes, respectively, after the first or second ovulation. These cycle irregularities certainly impose difficulties on estrus detection programs in postpartum buffaloes. Four main forms of anestrus i.e. true anestrus (inactive ovaries and small and medium sized anovulatory follicles), subestrus, prolonged luteal activity and ovarian cysts in addition to pregnancy are reviewed in this article. Differentiation between true anestrus and subestrus is particularly important in buffaloes because of their weak estrous signs. However, the accuracy of a single rectal palpation of the ovaries is limited with an overestimation of the frequency of true anestrus due to misdiagnosis of the corpus luteum. The possible causes are discussed.