Dynamics of Gastrointestinal Helminth Infections in Two Systems of Lamb Rearing

Ch r 0 u s t K.: Dynamics of Gastrointestinal Helminth Injections in Two Systems of Lamb Rearing. Acta vet. Brno 1995,64:171-177. The dynamics of faecal nematode, cestode and coccidia egg counts were investigated in two herds (I, 2) of ewes that had lambed in March and April and their lambs were turned out to pasture at the age of 1 to 4 weeks, and in one herd of ewes (3) that had lambed late in December and January and their lambs were turned out to pasture at the age of3 to 4 moriths. The pasture growth was monitored for the presence of infectious larvae of the gastrointestinal nematodes during the grazing period. In the lambs of Herds 1 and 2, the faecal counts of eggs (EPG) of the gastrointestinal nematodes and Moniezia spp. rose steeply already after the first month of the grazing period and this tendency continued until stopped by anthelmintic treatment. In the lambs of Herd 3, the steep rise in the faecal egg counts was preceded by a two-month period of a slow rise. The marked rise ofEPG of gastrointestinal nematodes during the lambing period (March, April), known as the "spring rise phenomenon", was observed ewes of Herds 1 and 2, but not of Herd 3. In the grazing ewes, the faecal egg counts were substantially lower than in their lambs. Ovoscopic and larvoscopic analyses of faecal samples collected from the ewes and lambs revealed infections with the following 10 genera/species of nematodes: Nematodirus spp., Ostertagia spp., Trichostrongylus spp., Chabertia ovina, Oesophagostomum spp., Bunostomum trigonocephalum, Cooperia spp., Haemonchus contortus, Strongyloides papillosus, and Trichuris ovis. The dynamics of the occurrence of La III on the pasture stand parallelled the findings in the lambs; maximum LPG values were recorded in late August and early September. Coccidiosis was no serious problem in the housed lambs and ewes in any of the three herds and OPG counts decreased continuously to a minimum during the grazing period. Gastrointestinal nematodes, Moniezia spp., Coccidia, dynamics of infection, lambs, ewes, conventional rearing, new system. The common local system of sheep herd management, particularly the winter (DecemberJanuary) lambing and the housing of the lambs up to the age of 3 to 4 months, was very unprofitable and required considerable state subsidies for their survival. The recent change of the economic environment and especially the application of the principles of market economy have given cause for a serious crisis in the sheep husbandry that can be overcome only by a considerable reduction of the costs of lamb rearing and meat production. Postponing of the lambing period to late March and April and rearing of lambs on pastures allow considerable savings of concentrates. Feeding of lambs with maternal milk combined with grazing is much more profitable (S k i' i van e k et al. 1991). However, the rearing of the lambs on pasture exposes them permanently to helminth infections from the first days of their life and will therefore require a new approach to the prevention and control. The objective of the present study was to investigate by quantitative and qualitative ovoscopic and larvoscopic methods the perannual dynamics of parasitic infections, particularly those by gastrointestinal helminths, to establish a basis for the elaboration of effective methods of control.