Segregation of natural and experimental gastrointestinal nematode infection in F2 progeny of susceptible Suffolk and resistant Gulf Coast Native sheep and its usefulness in assessment of genetic variation
Segregation of natural and experimental gastrointestinal nematode infection in F2 progeny of susceptible Suffolk and resistant Gulf Coast Native sheep and its usefulness in assessment of genetic variation
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DOI：
10.1016/j.vetpar.2006.02.043
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发表时间：
2006-08-31
影响因子：
2.6
通讯作者：
McGraw, R. A.
中科院分区：
文献类型：
--
作者：
Miller, J. E.;Bishop, S. C.;McGraw, R. A.
胃肠道线虫寄生是世界范围内小型反刍动物所关注的问题。生产力已经受到影响，因为这种线虫，特别是缠绕血线虫，已经对现有的驱虫剂产生了抗药性。一些绵羊品种和品种内的品系对感染具有相对抵抗力，这一特征可能有助于制定控制策略。将易感感染的萨福克羊与抗感染能力较强的墨西哥湾本地羊杂交，产生F-1后代。F-1代公羊与F-1代母羊杂交，产下227只F-2代母羊。这些F-2后代在两种自然感染条件下(一种在断奶时，另一种在夏季放牧后)和一种实验感染条件下，根据粪卵计数(FEC)和血细胞压积(PCV)评估感染水平的变异性。FEC和PCV在所有三个侵染期的变化幅度都很大，且存在年度变化。总体而言，三个感染期的粪便含卵量分别为167-149、933、0-31,400和17-114,667粒/克(EPG)，8.7-37.0%、7.333.0%和8.3-36.0%。这种感染分离是从敏感和抗性亲本品种中分离出的F-2后代所预期的。FEC和PCV在三个侵染期的遗传力分别为0.15、0.29和0.12，以及0.11、0.22和0.12。基于感染的分离、较大的遗传力和断奶后母体环境效应的下降，夏季自然感染可能是评估遗传变异的最佳模型。(C)2006爱思唯尔B.V.保留所有权利。
Gastrointestinal nematode parasitism is a concern to small ruminants worldwide. Productivity has been compromised because such nematodes, particularly Haemonchus contortus, have developed resistance to available anthelmintics. Some sheep breeds and lines within breeds are relatively resistant to infection, a trait that may be useful for developing control strategies. Suffolk sheep, which are susceptible to infection, were crossed with Gulf Coast Native sheep, which are more resistant to infection, to produce F-1 progeny. F-1 rams were bred to F-1 ewes which produced 227 F-2 offspring. These F-2 offspring were evaluated for variability in infection levels, based on fecal egg count (FEC) and blood packed cell volume (PCV), under two natural infection conditions (one at weaning and another after a summer grazing period) and one experimental infection. The range of both FEC and PCV was large for all three infection periods with annual variation. Overall, the range for the three infection periods, respectively, were 167-149, 933, 0-31,400 and 17-114, 667 eggs per gram (EPG) of feces and 8.7-:37.0%, 7.333.0% and 8.3-36.0%. This segregation of infection is what would be expected of F-2 progeny from susceptible and resistant parent breeds. Heritabilities of FEC and PCV for the three infection periods, respectively, were 0.15, 0.29 and 0.12, and 0.11, 0.22 and 0.12. Based on segregation of infection, larger heritabilities and maternal environment effects that declined after weaning, the summer natural infection was probably the best model for assessing genetic variation. (c) 2006 Elsevier B.V. All rights reserved.