Scotland's Rural College, Roslin Institute Building, Easter Bush, Midlothian EH25 9RG, United Kingdom.
Moredun Research Institute, Pentlands Science Park, Bush Loan, Midlothian EH26 0PZ, United Kingdom.
Animal. 2021 Apr;15(4):100185. doi: 10.1016/j.animal.2021.100185. Epub 2021 Feb 27.
Gastrointestinal parasitism is a global problem for grazing ruminants which can be addressed in a sustainable way through breeding animals to be more resistant to disease. This study estimates the genetic parameters of common and new disease phenotypes associated with natural nematode and coccidian infection in Scottish Blackface sheep to underpin future genetic improvement strategies for parasite control. Data on faecal egg counts (FEC) from different species of strongyle parasites and faecal oocyst counts (FOC) from coccidian parasites were collected on 3-month-old lambs together with a faecal soiling score in the breech area dagginess (DAG) and live weight (LWT). Faecal count data were obtained for Strongyles (FEC), Nematodirus (FEC) and Coccidia (FOC). Data from 3 731 lambs sampled between 2011 and 2017 were included. Faecal egg counts and DAG records were log-transformed prior to analysis. Data were analysed using linear mixed models. Average age at sampling was 92 days with a mean LWT of 24.5 kg. Faecal soiling was not evident in 69% of lambs. Coccidia were the most prevalent parasite (99.5%), while Strongyles and Nematodirus had a prevalence of 95.4% and 72.7%, respectively. Heritability estimates (±SE) were 0.16 ± 0.03, 0.17 ± 0.03, 0.09 ± 0.03, 0.09 ± 0.03 and 0.33 ± 0.04 for FEC, FEC, FOC, DAG and LWT, respectively. Strongyles faecal egg count had a strong and positive genetic correlation with FEC (0.74 ± 0.09) and a moderate positive correlation with FOC (0.39 ± 0.15) while DAG was negatively genetically correlated with LWT (-0.33 ± 0.15). The significant positive genetic correlations between FEC, FEC and FOC at 3 months of age show that co-selection of sheep for resistance to these different parasites is feasible. Selection for increased resistance to parasite infection is not expected to adversely affect live BW, as no significant antagonistic genetic correlations were found between LWT and FEC. There were significant antagonistic phenotypic and genetic relationships between DAG and LWT being -0.19 ± 0.02 and -0.33 ± 0.15, respectively, indicating that the expression of the manifestation of disease in lambs may be a more meaningful indicator of the impact of parasite burden on productivity.
胃肠道寄生虫病是放牧反刍动物的全球性问题，可以通过培育更能抵抗疾病的动物来以可持续的方式解决。本研究估计了苏格兰黑脸羊中与自然线虫和球虫感染相关的常见和新疾病表型的遗传参数，为寄生虫控制的未来遗传改良策略提供了依据。在 3 个月大的羔羊身上收集了来自不同种类的 Strongyles 寄生虫的粪便卵计数 (FEC) 和来自球虫寄生虫的粪便卵囊计数 (FOC) 以及臀部区域粪便污染评分 (DAG) 和活重 (LWT)。粪便计数数据包括 Strongyles (FEC)、Nematodirus (FEC) 和 Coccidia (FOC)。研究纳入了 2011 年至 2017 年间采集的 3731 只羔羊的数据。在分析之前，对粪便卵计数和 DAG 记录进行了对数转换。数据使用线性混合模型进行分析。平均采样年龄为 92 天，平均 LWT 为 24.5kg。69%的羔羊没有明显的粪便污染。球虫是最常见的寄生虫 (99.5%)，而 Strongyles 和 Nematodirus 的流行率分别为 95.4%和 72.7%。FEC、FEC、FOC、DAG 和 LWT 的遗传力估计值 (±SE) 分别为 0.16±0.03、0.17±0.03、0.09±0.03、0.09±0.03 和 0.33±0.04。Strongyles 粪便卵计数与 FEC (0.74±0.09) 呈强正遗传相关，与 FOC (0.39±0.15) 呈中度正相关，而 DAG 与 LWT 呈负遗传相关 (-0.33±0.15)。3 个月龄时 FEC、FEC 和 FOC 之间显著的正遗传相关性表明，对这些不同寄生虫的抵抗力进行共同选择是可行的。预计对寄生虫感染的抵抗力增加的选择不会对活重产生不利影响，因为 LWT 和 FEC 之间没有发现显著的拮抗遗传相关性。DAG 和 LWT 之间存在显著的拮抗表型和遗传关系，分别为-0.19±0.02 和-0.33±0.15，表明羔羊疾病表现的表达可能是寄生虫负担对生产力影响的更有意义的指标。
