Equine Chorionic Gonadotropin in African N’dama Cattle

Given its rustic nature, its butchery quality and its trypanotolerance, the N’Dama breed represents a significant potential for developing African cattle breeding [6]. To date, its zootechnical performance and reproductive characteristics have been the subject of relatively little work. The use of selection programmes and artificial insemination are highly significant challenges for developing and improving this breed. Given the conditions under which these cattle are bred and hence the difficulty of inseminating animals when heat is observed, synchronised hormonal protocols have to be applied to allow systematic inseminations. Many different timed artificial insemination (TAI) hormonal protocols have been used in dairy and beef cattle under tropical conditions [2]. Some are based on the use of PGF associated or not to GnRH. The others involve the administration of progestagens for five to nine days, followed by an injection of PGF2α and equine chorionic gonadotropin (eCG). Such protocols have been shown to allow systematic insemination [17, 20]. Exogenous progesterone suppresses LH release, and induces the appearance of a new wave of follicular growth four to five days later [12]. PGF2α is injected one or two days before the progesterone-based treatment is stopped or when it is stopped. This treatment aims to induce luteolysis in any corpora lutea (CL) present in cycled females. Administering eCG (equine Chorionic Gonadotropin) when the PRID is removed improves follicular growth and the ovulatory response. Stimulating the follicular growth and estrogens synthesis, eCG can improve the ovulatory response to a synchronization protocol without adverse effect following subsequent treatment [2]. The dosage of eCG should, nevertheless, be adjusted to the cycled or anoestrus status of the animal, so as not to induce superovulation, which is likely to lead to multiple pregnancies. The dosage and effects of eCG in female N’Dama have been the subject of relatively ABSTRACT