Uriarte J, Valderrábano J
Servicio de Investigacion Agraria (D.G.A.), Zaragoza, Spain.
Vet Parasitol. 1990 Nov;37(3-4):243-55. doi: 10.1016/0304-4017(90)90008-y.
The effect of forward (F) and lateral (L) creep grazing, as two possible management alternatives of intensive production systems, on the gastro-intestinal nematode epidemiology of ewes and lambs was studied. Two groups of Romanov x Rasa Aragonesa ewes rearing twins and maintained on an autumn-contaminated pasture at a mean stocking density of 35 ewes ha-1, were used. Measurements were made of the population of infective larvae on the pasture, level of serum pepsinogen, worm eggs in faeces of ewes and lambs, and lambs' growth rate. In addition, post-mortem worm counts from 'indicator' lambs were used to establish the level of infection at each rotational grazing cycle. Two different waves of nematode infection were identified. In both treatments, the over-wintering larvae were responsible for the first outbreak of parasitism which was particularly important for lambs on Treatment F. The second wave of infection apparently came up with several overlapped L3 generations and had different effects on the animals of each group. While early pasture contamination was suffered by the lambs of Treatment F, lambs on Treatment L were not seriously affected until the end of the third grazing cycle (end of May). The different grazing behaviour of lambs in both treatments appeared to be related to the outbreak of parasitism in lambs. The general pattern of liveweight gains was similar for both groups of animals. However, during the first 90 days on pasture lamb growth rate under Treatment L (193 g day-1) was significantly higher than that under Treatment F (164 g day-1). The serum pepsinogen values, worm burdens and liveweight gains indicate that under intensive systems where lateral creep grazing is allowed for lambs, the level of parasite infection is maintained within acceptable limits for the first 90 days on pasture with lambs' growth rate close to their potential. However, the parasitic consequences of grazing under a forward creeping system indicate that anthelmintic drenchings should be used at lambing and at 3-week intervals thereafter during the first 42 days on pasture, after which the risk of contamination from the over-wintering population is over.
研究了作为集约化生产系统两种可能管理方式的正向（F）和侧向（L）蠕行放牧对母羊和羔羊胃肠道线虫流行病学的影响。使用了两组罗曼诺夫×阿拉贡纳萨母羊，每组母羊产双羔，在秋季受污染的牧场上以每公顷35只母羊的平均饲养密度饲养。对牧场上感染性幼虫数量、血清胃蛋白酶原水平、母羊和羔羊粪便中的虫卵以及羔羊生长速度进行了测量。此外，利用“指示”羔羊的死后蠕虫计数来确定每个轮牧周期的感染水平。确定了两波不同的线虫感染。在两种处理中，越冬幼虫导致了首次寄生虫病爆发，这对处理F组的羔羊尤为重要。第二波感染显然出现了几个重叠的L3世代，对每组动物产生了不同影响。处理F组的羔羊早期受到牧场污染，而处理L组的羔羊直到第三个放牧周期结束（5月底）才受到严重影响。两种处理中羔羊不同的放牧行为似乎与羔羊寄生虫病的爆发有关。两组动物的体重增加总体模式相似。然而，在牧场上的前90天，处理L组羔羊的生长速度（每天193克）显著高于处理F组（每天164克）。血清胃蛋白酶原值、蠕虫负荷和体重增加表明，在集约化系统中，若允许羔羊进行侧向蠕行放牧，在牧场上的前90天内寄生虫感染水平可维持在可接受范围内，羔羊生长速度接近其潜力。然而，正向蠕行放牧系统下放牧的寄生虫后果表明，应在产羔时以及此后在牧场上的前42天内每隔3周进行一次驱虫，此后越冬种群的污染风险结束。
