Mitchell G B, Fitzsimons J
Res Vet Sci. 1983 Jul;35(1):100-5.
Despite the widespread adoption of clean grazing systems in lowland sheep flocks, detailed parasitological investigations had not previously been carried out on such flocks. A trial was therefore conducted on two commercial flocks: a traditional permanent pasture flock (A) and one operating a system of clean grazing (B), and on an East of Scotland College flock (C) which had operated a clean grazing system for eight years. Ewe and lamb worm egg output, pasture larval levels and lamb liveweight gains were monitored and tracer lambs were grazed during July and August on each farm. Under clean grazing conditions on farm C all parasitological parameters were lower than on both commercial farms. However, in the commercial flocks comparable contamination was evident from midsummer onwards and tracer lambs grazed during August on farm B had significantly greater worm burdens than on the other two farms. The differences observed between the flocks were thought to be due to greater residual contamination by overwintered larvae in both commercial flocks while the higher worm burdens in August on farm B probably resulted partly from incomplete control of the periparturient rise in ewe faecal egg output and partly to autoinfection of the lamb crop. It was concluded that farm C grazing was the cleanest. Considerable contamination was present on farm A while farm B occupied an intermediate position which resulted in considerable worm burdens in lambs grazing during the latter part of the season.
尽管低地羊群中广泛采用了清洁放牧系统，但此前尚未对这类羊群进行过详细的寄生虫学调查。因此，在两个商业羊群中进行了一项试验：一个是传统的永久牧场羊群（A），另一个采用清洁放牧系统（B），还有一个是苏格兰东部学院的羊群（C），该羊群已采用清洁放牧系统八年。对母羊和羔羊的蠕虫卵产量、牧场幼虫水平以及羔羊体重增加情况进行了监测，并在7月和8月期间在每个农场放牧了追踪羔羊。在农场C的清洁放牧条件下，所有寄生虫学参数均低于两个商业农场。然而，在商业羊群中，从仲夏开始就有明显的类似污染情况，8月在农场B放牧的追踪羔羊的蠕虫负担明显高于其他两个农场。羊群之间观察到的差异被认为是由于两个商业羊群中越冬幼虫的残留污染更大，而农场B在8月蠕虫负担较高可能部分是由于对母羊产羔期粪便卵产量上升控制不完全，部分是由于羔羊群体的自身感染。得出的结论是，农场C的放牧是最清洁的。农场A存在大量污染，而农场B处于中间位置，这导致在季节后期放牧的羔羊有相当大的蠕虫负担。
