Study of oestrus of N’Dama and Baoulé trypanotolerant cows in Côte d’Ivoire. II. Hormonal component (LH)

Abstract

The aims of this study were to evaluate the time elapsed between the injection of prostaglandin F2α and the onset of oestrus (and the duration of oestrus) of cows from two Bos taurus (trypanotolerant) breeds: N’Dama and Baoulé (West African shorthorn) and to measure the plasma peripheral concentration of LH around oestrus. The study was performed in a humid tropical zone (Bouaké, Côte d’Ivoire) during the dry hot season from 7 N’Dama and 8 Baoulé cycling cows. The onset of oestrus of the cows was observed 59.9 ± 9.2 hours (7 N’Dama) and 91.7 ± 10.3 h (6 Baoulé) after injection with 15 mg of luprostiol (prostaglandin F2 α analog). The base level of LH was 1.5 ± 0.5 ng/ml (N’Dama) and 1.8 ± 0.7 ng/ml (Baoulé). The LH peak was typical in 4 N’Dama and 3 Baoulé cows and had the following parameters : beginning of the surge 5.3 h after onset of oestrus: duration 6-7 h, maximum level 60 ng/ml. The two main features of this study were therefore: the onset of oestrus began significantly earlier (30 h approximately) in N’Dama than in Baoulé cattle after injection of prostaglandin F2α; the peripheral LH concentrations from these two breeds appeared to have a similar evolution to that of European cattle in temperate climates.