Genetic parameters of animal traits associated with coccidian and nematode parasite load and growth in Scottish Blackface sheep

Gastrointestinal parasitism is a global problem for grazing ruminants which can be addressed in sustainable way through breeding animals to more resistant disease. This study estimates the genetic parameters of common and new disease phenotypes associated with natural nematode coccidian infection Scottish Blackface sheep underpin future improvement strategies parasite control. Data on faecal egg counts (FEC) from different species strongyle parasites oocyst (FOC) were collected 3-month-old lambs together soiling score breech area dagginess (DAG) live weight (LWT). Faecal count data obtained Strongyles (FECS), Nematodirus (FECN) Coccidia (FOC). 3 731 sampled between 2011 2017 included. DAG records log-transformed prior analysis. analysed using linear mixed models. Average age at sampling was 92 days mean LWT 24.5 kg. not evident 69% lambs. most prevalent (99.5%), while had prevalence 95.4% 72.7%, respectively. Heritability (± SE) 0.16 ± 0.03, 0.17 0.09 0.03 0.33 0.04 FECS, FECN, FOC, LWT, strong positive correlation FECN (0.74 0.09) moderate FOC (0.39 0.15) negatively genetically correlated (? 0.15). The significant correlations months show that co-selection resistance these feasible. Selection increased expected adversely affect BW, as no antagonistic found FEC. There phenotypic relationships being ? 0.19 0.02 0.15, respectively, indicating expression manifestation may meaningful indicator impact burden productivity.