Study of gastro-intestinal stronglyosis in a sheep flock on permanent pasture. 1. Sheep parasitism in 1977.

An epidemiological study aimed at defining gastro-intestinal parasitism in sheep qualitatively and quantitatively was carried out in the Limousin area in France. Five lambs were sacrificed regularly every 4 weeks from May till January of the following year. Complete parasite counts were performed on these animals as well as measurements of the plasma level of pepsinogen. In order to define the influence of parasitism on the growth of the animals, the weight gains of lambs treated regularly and untreated lambs were compared. The results of post-mortem examination show that parasitism is mainly linked to the incidence of strongyles. Other observations in the flock have shown that Moniezosis may also play a non-negligeable part. The parasitic level, already high after one month at pasture, reached its maximum in July-August 1977 and was marked by a very high level of parasitism. Among these species found, two played an essential part: Ostertagia circumcincta and Haemonchus contortus. A study of the growth of the lambs showed that within 6 months, the weight gain of the treated animals was twice that of the untreated animals. The effects of parasitism were worsened by the low fodder value of the pasture and the occurrence of overgrazing. The blood pepsinogen measurements confirmed the usefulness of this technique in establishing the mean level of infestation of a flock by parasites of the abomasum. It seems that in some cases it could help to define the succession of peaks of infestation by different species.