The susceptibility of Djallonke and Djallonke-Sahelian sheep to Trypanosoma congolense and helminth infection under different diet levels

Forty two Djallonke and 27 Djallonke-Sahelian crossbred sheep were compared during 34 weeks for their disease resistance and productivity in a multifa ctorial experiment including trypanosome infection, helminth infections and dietary level. Eight treatment combinations were formed in which the two b reeds were balanced. Pyrexia was observed following trypanosome infection a nd was not different between the two breeds. However, a significant higher parasitaemia level, a shorter prepatent period and a lower antibody respons e in the crossbreds following infection, indicated a significant reduction of the trypanotolerance and confirmed the genetic origin of the trait. Neit her helminth infection nor dietary level influenced the onset and level of parasitaemia or the level of antibody response following trypanosome infect ion. Trypanosome infection, helminth infection and low supplementary feedin g caused independently significant reductions in PCV level and weight gain but these declines were not worse in crossbreds as compared to Djallonke. I ndependently, of the studied factors, crossbreds were generally heavier tha n Djallonke and also grew faster, especially during the second phase of the study. Crossbreds had significantly higher mean nematode egg output (epg) compared to Djallonke sheep but reduction of epg following deworming was si milar in both breeds. The lower epg in the Djallonke breed indicated an inn ate resistance to helminths and/or more efficient immune response. Trypanos ome infection tended to increase epg, confirming the immunosuppressive effe ct of the former. The higher body temperature in the Djallonke compared to crossbreds suggested a better heat tolerance in the former breed. From this study it was concluded that Djallonke-Sahelian crossbred sheep in spite of a reduced trypanotolerance and lower resistance to helminth infect ion, posses a higher potential to intensify mutton production as compared t o the pure Djallonke. However, appropriate measures should be taken to limi t disease and stress factors in order to optimise production environment fo r this crossbred sheep, (C) 1999 Elsevier Science B.V. All rights reserved.