Studies on caprine responsiveness to nematodiasis: Segregation of male goats into responders and non-responders

Eighty-three 2-4-year-old intact male goats exposed to a combination of artificial and natural challenge were segregated into responders and non-responders by ranking of weekly faecal egg counts (FECs). Retrospective analysis of samples over a 15-week-period showed responders had a statistically lower mean FEC than non-responders. Estimates of repeatability between consecutive egg counts were significant in both groups. The 6 top responders and bottom non-responders were subsequently given an artificial trickle challenge with Teladorsagia circumcincta and Trichostrongylus vitrinus. Mean faecal egg output was significantly lower in responders than non-responders. Peripheral eosinophil numbers following challenge were significantly greater in responder than non-responder goats. Abomasal and intestinal worm burdens were considerably lower in responders, with evidence of retardation of worm development compared to non-responders. Both abomasal and jejunal tissue eosinophil numbers were significantly higher in responders, although there was no difference in mucosal mast cell or globule leucocyte numbers. These results suggest that under temperate climatic conditions, it is possible to segregate male goats into responders and non-responders on the basis of simple parasitological criteria.