[Epidemiological studies on infections by Nematodirus species in sheep]
1991
Valenzuela, G. | Quintana, I. | Fernandez, C. (Universidad Austral de Chile, Valdivia (Chile). Fac. de Ciencias Veterinarias)
In order to determine the number of Nematodirus spp. eggs in faeces of naturally infected sheep, an epidemiological study was undertaken in two farms under a silvopastoral system: In Farm "A", Romney and Suffolk x Romney cross bred ewes were used and maintained in paddocks with native pasture and subterranean clover planted with Pinus radiata D. Don, Castanea sativa and Pseudotsuga menziesii. In Farm "B", Romney and Suffolk x Romney crossbred and Boorola x Romney ewes were used and maintained in paddocks planted with P. radiata D. Don. In both farms, sheep were divided into three age groups: 0 to one year old: two groups, and one to three year old: one group. Sheep were monitored monthly during a period of 23 in Farm "A" and 26 months in Farm "B". Faeces samples were examined by the McMaster technique. Lambs from Farm "A" showed a sharp increase in egg number reaching a peak of 342 and 206 e.p.g. when they were four and five months old respectively and of 225 and 150 e.p.g. in Farm "B" when they were seven and eight months old. Then, egg number decreased gradually in Farm "A" and sharply in Farm "B", until they were eight to nine month old when the number was similar to the adult sheep. It was observed that there were no differences in the trend of egg output in lambs and adult sheep when compared with the trend under traditional management observed by other authors. Lambs of up to eight month old were highly susceptible to the infection and produced a greater contamination of the pasture
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