Ciordia H, Stuedemann J A, Ernst J V, Campbell H C, Wilkinson S R
Am J Vet Res. 1980 Jun;41(6):893-8.
Two established tall fescue pastures were used in a 4-year study of the relationship between the level of gastrointestinal parasitism in cattle and the level of nitrogen fertilization of the pasture. One pasture was fertilized with 224 kg of NH4NO3/ha each year and served as the control. A second pasture, referred to as the low-fertilized (LF) pasture, was fertilized with N at 84 kg/ha the first year and 74 kg/ha in each of the next 3 years. Both pastures were stocked with Angus cows (2.5/ha) and their calves. Rectal fecal samples obtained every 6 weeks from 10 cows and as many calves as possible in each pasture were examined for nemotode eggs and coccidia oocysts. Two calves from each group were slaughtered at the end of each of the last 3 years to determine the numbers and species of parasites. Cows had significantly lower egg counts than did the calves. Egg counts did not differ between the two groups of cows, but the control cows had higher average weights than the cows on the LF pasture. Control calves had significantly lower egg counts than the calves on the LF pasture, but only slightly higher mean adjusted 205-day weights. At necropsy, significantly fewer worms were recovered from the controls (17,977) than from the LF-pastured calves (52,332). Cooperia oncophora was the predominant species. The level of coccidia infection did not differ between the two groups of cows and calves. The greater availability of forage in the control than in the LF pasture probably was responsible for the lower level of parasitism in the control calves and for the greater weight gains made by the control cows and calves.
在一项为期4年的研究中，使用了两块已建成的高羊茅牧场，以研究牛胃肠道寄生虫感染水平与牧场氮肥施用量之间的关系。一块牧场每年施用224千克硝酸铵/公顷作为对照。另一块牧场，即低施肥（LF）牧场，第一年施氮量为84千克/公顷，接下来3年每年施氮量为74千克/公顷。两块牧场都饲养了安格斯母牛（2.5头/公顷）及其犊牛。每6周从每个牧场的10头母牛以及尽可能多的犊牛中采集直肠粪便样本，检查其中的线虫卵和球虫卵囊。在最后3年的每年年末，从每组中挑选2头犊牛进行屠宰，以确定寄生虫的数量和种类。母牛的虫卵计数显著低于犊牛。两组母牛的虫卵计数没有差异，但对照牧场的母牛平均体重高于LF牧场的母牛。对照牧场的犊牛虫卵计数显著低于LF牧场的犊牛，但平均校正205日龄体重仅略高。尸检时，从对照牧场犊牛体内回收的蠕虫数量（17,977条）明显少于LF牧场犊牛（52,332条）。牛食道口线虫是主要种类。两组母牛和犊牛的球虫感染水平没有差异。对照牧场的草料供应比LF牧场更充足，这可能是对照牧场犊牛寄生虫感染水平较低以及对照牧场母牛和犊牛体重增加更多的原因。
