Mitchell G B, Fitzsimons J, Mathieson A O
Res Vet Sci. 1984 May;36(3):364-9.
An investigation of sources of helminth infection was carried out on three flocks: a traditional permanent pasture flock (A), one operating a 'clean' grazing system (B), and an East of Scotland College flock (C) which had operated a clean grazing system for nine years. Ewe and lamb worm egg output and pasture larval levels were recorded and tracer lambs were grazed during July and August on each farm. Considerable contamination was present on farm B fields compared with farms A and C, which resulted in higher worm burdens in late summer in farm B tracer lambs and lower weight gains. The main source of this infection was thought to be ewe periparturient egg output, as 21 per cent of ewes had positive worm egg counts over the lambing period. Differences in management practices between farms B and C, eg, earlier stocking of farm B fields, were also considered contributory factors.
一个是传统的永久牧场羊群（A），一个采用“清洁”放牧系统的羊群（B），以及苏格兰东部学院的一个羊群（C），该羊群已采用清洁放牧系统九年。记录了母羊和羔羊的蠕虫虫卵产量以及牧场幼虫水平，并于7月和8月在每个农场放牧了示踪羔羊。与农场A和C相比，农场B的田地存在大量污染，这导致农场B的示踪羔羊在夏末的蠕虫负担更高，体重增加更低。这种感染的主要来源被认为是母羊围产期的虫卵产量，因为21%的母羊在产羔期的蠕虫虫卵计数呈阳性。农场B和C之间管理方式的差异，例如农场B田地更早的放牧密度，也被认为是促成因素。
