Williams J C, Knox J W, Marbury K S, Swalley R A, Willis R E
Department of Veterinary Science, LSU Agricultural Center, Baton Rouge 70803.
Vet Parasitol. 1989 Oct;33(3-4):265-81. doi: 10.1016/0304-4017(89)90136-2.
Four groups of 17 crossbred beef weaners were used in an experiment which extended from 14 November 1985 to 8 October 1986 (328 days). All groups began grazing on separate, contaminated pastures at a stocking rate of 5.3 cattle ha-1 and the different treatments were: Group 1, ivermectin (IVM) injectable X 1 (200 micrograms kg-1) on 14 November only, with provision for individual salvage treatment; Group 2, IVM X 3 on 14 November, 4 February and 2 July; Group 3, IVM X 2 on 14 November and 2 July; Group 4, fenbendazole (FBZ) paste X 2 (5 mg kg-1) on 14 November and 2 July. Pairs of parasite-free tracer calves were grazed on all group pastures for 1 month at the beginning of the experiment (13 November-12 December and in spring (1 April-1 May). Yearling cattle from each group were randomly selected and removed from pasture during spring (n = 2 per group, 3 April) and at the end of the experiment (n = 3 per group, 8 October) for slaughter analysis of worm population characteristics and observation of gross pathology in the abomasum and intestinal tract. At monthly intervals, all cattle were weighed and fecal egg counts, pasture larval counts and plasma pepsinogen values were determined. The results of this investigation demonstrated that three IVM treatments of weaner-yearling beef cattle during year-long grazing, were more effective than a single IVM treatment or two treatments with IVM or FBZ in the enhancement of productivity and protection from the effects of infection with nematode parasites.
1985年11月14日至1986年10月8日（共328天）进行了一项实验，使用了四组，每组17头杂交肉牛断奶犊牛。所有组均开始在单独的受污染牧场上放牧，放养密度为每公顷5.3头牛，不同处理方式如下：第1组，仅在11月14日注射一次伊维菌素（IVM）（200微克/千克），并提供个体挽救治疗；第2组，在11月14日、2月4日和7月2日进行三次IVM治疗；第3组，在11月14日和7月2日进行两次IVM治疗；第4组，在11月14日和7月2日使用两次芬苯达唑（FBZ）膏剂（5毫克/千克）。在实验开始时（11月13日至12月12日）和春季（4月1日至5月1日），每组牧场放牧一对无寄生虫的示踪犊牛1个月。在春季（每组2头，4月3日）和实验结束时（每组3头，10月8日），从每组中随机挑选一岁牛，从牧场中移出，用于分析蠕虫种群特征并观察皱胃和肠道的大体病理学。每隔一个月，对所有牛进行称重，并测定粪便虫卵计数、牧场幼虫计数和血浆胃蛋白酶原值。这项调查的结果表明，在长达一年的放牧期间，对断奶一岁肉牛进行三次IVM治疗，在提高生产力和预防线虫寄生虫感染方面，比单次IVM治疗或两次IVM或FBZ治疗更有效。
