Risk Factors and Treatment of Postpartum Anestrus in Cattle: The Case of Zebu

This literature review reports on risk factors for postpartum anoestrus in zebus and their potential treatments. Prolonged postpartum anestrus is one of the major factors limiting reproductive efficiency in cattle, particularly in Bos indicus cows in tropical regions, as it prevents a calving interval of 365 days from being achieved. During anestrus, ovulation does not occur despite ovarian follicular development, as the growing follicles do not reach maturity. This period is very variable and depends on various factors whose importance is relative or, on the contrary, essential. Some are specific to the animal (breastfeeding or food); others relate more to its social environment, season sanitary conditions. Several hormonal treatments have been used to induce ovulation and cyclicity in postpartum cows. Generally speaking, given the inconsistency of the effects or even their lack of practicability, treatments using a single or repeated injection of a gonadotropin-releasing hormone (GnRH) have been gradually abandoned in favour of progestagens. These are administered for 8 to 12 days on a continuous basis in the form of a subcutaneous implant (Crestar®), a vaginal coil (PRID®) or a CIDR. A prostaglandin injection is given two days before the implant is removed. The addition of an ECG treatment at the time of device removal, which increased plasma progesterone concentrations and pregnancy rates in anestrous postpartum suckled Bos indicus cows, may be useful to improve reproductive performance. This improvement requires a better understanding of the effect of different risk factors on the recovery of postpartum cyclicity.