Seroprevalence of Neospora caninum antibodies and its consequences for reproductive parameters in dairy cows from Dakar–Senegal,West Africa

The aim of this study was to determine the seroprevalence of Neospora caninum antibodies and its effects on reproductive parameters in cows in intensive dairy herds in Dakar. Randomised blood samples were taken for serology from 196 cows in four herds with a history of sporadic abortion. All of the sera were assayed for antibodies against N. caninum, Candida guillermondii, Coxiella burnetii, and Chlamydophila sp. The associations between serostatus and reproductive parameters (abortion, number of inseminations to conception, and calving to conception interval) were assessed over a period of 5 years (2004–2008). The seroprevalence of N. caninum antibodies in dairy cattle was 17.9%. The local Gobra breed and crossbreeds had higher levels of N. caninum antibodies than exotic breeds (p < 0.05). For the most recent pregnancies, seropositive cows required more inseminations to establish conception than seronegative cows (p < 0.05). The results indicate that dairy cattle from Dakar are exposed to N. caninum. Neosporosis should, therefore, be systematically considered as a cause when the calving to conception interval is prolonged.     

Nutrient constraint and yield potential of rice on upland soil in the south of the Dahoumey gap of West Africa

With the objective of improving rice productivity and generating additional knowledge on rice production in Africa, field experiments were conducted for two consecutive seasons of 2005 and 2006 in Southern Benin. Terre de barre soils at the WARDA experimental station and Niaouli, and the plinthic Ferralsols of Cana were investigated. A complete fertilizer (Fc) composed of N, P, K, Ca, Mg and Zn was used to assess NERICA.4 (upland rice) root development and grain yield (GY). Similar observations were made in treatments with a specific nutrient excluded from Fc (Fc–N, Fc–P, Fc–K, Fc–Ca, Fc–Mg and Fc–Zn). A grain yield of up to 1.4 t ha^?1 (Fc–N) and higher root densities for Fc and Fc–Mg at 20–60 cm were attained. Maximum reductions in yield and rooting depth were observed for Fc–P (27%, 27%), Fc–K (30%, 14%) and Fc–Zn (32%, 2%). Drought occurrence, a high C/N ratio and soil acidity influence the effects of nutrients on rice. Removal of N from basal fertilizer was recommended to reduce the effect of mid-season drought. It is suggested that the critical level of K in the soils of West Africa be adjusted to 0.40 cmol kg^?1 for upland rice.