School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia.
Vet Parasitol. 2011 Jun 30;179(1-3):130-6. doi: 10.1016/j.vetpar.2011.01.063. Epub 2011 Mar 3.
The aim of this experiment was to investigate the effect of Haemonchus contortus infection on rumen function and digestion of Merino sheep from lines divergently selected for genetic resistance to H. contortus. Rumen function and whole-tract digestibility were determined in 29 Merino weaner wethers from the CSIRO Haemonchus selection flock, increased resistance to Haemonchus (IRH), decreased resistance to Haemonchus (DRH) and random bred control (C) selection lines. Wethers were fed a restricted low quality roughage diet (5.9 MJ ME/kg DM, 29 g MP/kg DM) to maintain weight and were either uninfected (NIL) or infected with H. contortus (INF). Measurements were taken at week 7 of infection, while animals were housed in metabolic crates. Animals were then euthanased to determine abomasal worm counts. IRH had significantly lower worm egg count than DRH and C lines however, adult worm and larval counts, though lower in IRH animals, did not differ significantly. DM and OM digestibility and in sacco degradability of IRH and DRH selection lines were greater than C animals. Rumen function of animals from the IRH line was altered in response to H. contortus infection with an increase in fluid outflow and turnover rate and a decrease in propionic acid concentration. These changes may be a component of a greater host resistance and begin to explain the failure of IRH animals to translate lower worm egg count into greater bodyweight gain.
本实验旨在研究感染捻转血矛线虫对不同遗传抗性选择的美利奴羊的瘤胃功能和消化的影响。从 CSIRO 捻转血矛线虫选择羊群中选择了 29 只美利奴断奶公羊，分为对捻转血矛线虫具有高遗传抗性（IRH）、低遗传抗性（DRH）和随机繁殖对照（C）选择系。公羊以低质量粗饲料（5.9MJ ME/kg DM，29g MP/kg DM）限制喂养以维持体重，并分为未感染（NIL）或感染捻转血矛线虫（INF）组。在感染的第 7 周进行测量，同时动物被安置在代谢笼中。然后，对动物进行安乐死以确定网胃中的虫体计数。IRH 的虫卵计数明显低于 DRH 和 C 系，但 IRH 动物的成虫和幼虫计数虽较低，但差异不显著。IRH 和 DRH 选择系的 DM 和 OM 消化率以及在囊中降解率均高于 C 动物。IRH 系动物的瘤胃功能因感染捻转血矛线虫而发生改变，表现为液体流出量和周转率增加，丙酸浓度降低。这些变化可能是宿主抗性增强的一个组成部分，并开始解释 IRH 动物未能将较低的虫卵计数转化为更大的体重增加的原因。
