Schmidt E E, Suarez V H, Cabaret J
Facultad de Ciencias veterinarias, Universidad de la Pampa, Argentina.
Vet Res. 1998 Mar-Apr;29(2):139-48.
Breeding cattle for resistance to nematode infection is mostly based on egg excretion. This, however, does not allow for generic identification of the nematodes involved. Unless we know whether the selected resistance is directed against one or several particular genera, a strong bias could be introduced in the selection programs. In order to estimate the likelihood of this potential bias we investigated nematode genera diversity in the progeny of four sires in 1992 and seven sires in 1994. Three of the four Aberdeen Angus sires used in 1992 were related while the seven sires in 1994 were unrelated. Diversity was assessed using at least ten individual faecal cultures for each progeny group during each of the two sampling periods (beginning and end of grazing period, April and September). It was estimated by the relative proportion of each genera (Ostertagia, Cooperia, Haemonchus, Trichostrongylus and Oesophagostomum) or by either the Shannon (genera diversity) or Pielou (genera evenness) index. The Shannon index was repeatable when measured at 2-week intervals within the same progeny group on ten random faecal samples. No significant difference was recorded between sire genera diversity over the two sampling periods. This indicated that hosts have a limited effect on the nematode genera diversity as assessed by faecal cultures, and that the selection of resistant hosts could probably be achieved using faecal egg counts.
培育抗线虫感染的肉牛主要基于虫卵排泄情况。然而，这无法对所涉及的线虫进行种类鉴定。除非我们知道所选的抗性是针对一个还是几个特定属，否则在选择计划中可能会引入严重偏差。为了评估这种潜在偏差的可能性，我们在1992年调查了4头公牛后代以及在1994年调查了7头公牛后代中的线虫属多样性。1992年使用的4头阿伯丁安格斯公牛中有3头有亲缘关系，而1994年的7头公牛没有亲缘关系。在两个采样期（放牧期开始和结束时，即4月和9月）的每个后代组中，使用至少10个个体粪便培养物来评估多样性。通过每个属（奥斯特他线虫属、古柏线虫属、血矛线虫属、毛圆线虫属和食道口线虫属）的相对比例，或者通过香农指数（属多样性）或皮洛指数（属均匀度）来估计。当在同一后代组内对10个随机粪便样本每隔2周进行测量时，香农指数是可重复的。在两个采样期之间，公牛的属多样性没有显著差异。这表明宿主对通过粪便培养评估的线虫属多样性影响有限，并且使用粪便虫卵计数可能可以实现抗性宿主的选择。
