Relationship between genetic diversity in the nematode Trichostrongylus colubriformis and breeding management in ten dairy-goat farms.

Ten dairy-goat farms were investigated in center-west of France for genetic variability of Trichostrongylus colubriformis in relation to breeding management. Farm management data were obtained from a questionnaire. Genetic variability was based on two polymorphic enzymes, malate dehydrogenase (MDH) and glucose-phosphate isomerase (GPI). After their establishment, the farms were subsequently isolated from introduction of strongyle worms as shown in the questionnaire; this was also suggested by the absence of a relationship between genetic variability and distance between farm locations. The genetic variability which was recorded could then be ascribed in part to the influence of management. The breeding management estimates combined the fact that animal breeding was the main economic resource; that goats were or were not the only animal bred; and that there was or was not free access to exercise yards in winter. The farms that were similar on the basis of breeding management, were also similar in the frequency of allozymes, indicating that the chosen allozymes were not neutral in respect to environment. Genetic variability was not related to the frequency of T. colubriformis in the strongyle community, this being possibly due to the fact that our farm samples predominantly harboured T. colubriformis. Between-farm genetic variability was positively correlated to the size of herd (P < 0.01), probably due to the fact that larger herds were originally constituted from several different herds.