Hormonal treatments for the synchronisation of oestrus in dairy goats raised in the tropics.

In tropical areas, local goats are often reported as being able to reproduce throughout the year, whereas an influence of season is found to be a factor when importing different dairy breeds. In these areas, oestrus synchronisation in goats is of interest for both technical (synchronisation of kidding, adjustment to forage availability or to continuous milk supply) and genetic reasons (dissemination of improved genotypes by AI). The use of a progestagen vaginal sponge combined with equine chorionic gonadotrophin (eCG)-cloprostenol injections remains an efficient tool to achieve synchronisation in temperate and tropical zones. However, the oestrus synchronisation treatments currently used for goats in tropical regions were originally developed for goats bred in temperate regions. For this reason, several alternative possibilities for improving the efficiency of the hormonal treatment are evaluated. Oestrus synchronisation with luteolytic agents is efficient (resulting in more than 70% of goats in oestrus) and it takes into account female cyclicity. In developing regions of the tropics, the use of buck teasing appears to be a promising approach to control oestrus and ovulation. The use of this technique provides 60% of females in oestrus within 5 days of introducing the bucks. Considering the availability of nutrients as the ultimate regulator of reproduction in the tropics, the control of nutritional condition is essential before the use of hormonal treatments for oestrus synchronisation in goats bred in these regions takes place.