Analysis of the relationship between land use and the parasitism of sheep during their transhumance.

摘要

The aims were to identify the parasite communities and to relate the kinetics of infection to environmental factors during summer transhumance. A survey of parasitism of a sheep flock from the Southeast of France was conducted during its summer transhumance in the Southern Alps. The flock was composed of 700 young Merino of Arles ewes. The 152 days of transhumance were spent grazing 3 pastures at an altitude of 1200 m, 4 pastures at 1700 m, and then spending 83 days between 2000 and 2500 m before returning back down to the same groups of lower pastures. The species of parasites present were identified in 5 tracer lambs collected 4 times during the survey. In addition, grass and faecal pellets on the pastures and on 28 alpine grasslands in the upper valley were sampled every month to look for the infective larvae of the gastrointestinal nematodes. Data for these grasslands and their use by the flock were available from the previous year. The main parasite species detected were the nematodes Teladorsagia circumcincta and Nematodirus spp.; the tracers collected about 4000 worms, mainly on the pre-alpine pastures. In the higher valley, considerable differences between the different areas were observed with regards to grass availability, pellet deposition and flock frequency. The pellets acted as a reservoir for over-wintering larvae. The most contaminated areas were those that had been grazed during August of the previous year. These findings were used to optimize flock management so as to limit infection and to prevent deterioration of the higher grasslands due to over-grazing and erosion..