Genomic evaluation of resistance to Haemonchus contortus in a South African Dohne Merino flock

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dc.contributor.author Dlamini, Njabulo Mark
dc.contributor.author Visser, Carina
dc.contributor.author Snyman, Margaretha A.
dc.contributor.author Soma, P.
dc.contributor.author Muchadeyi, Farai Catherine
dc.date.accessioned 2019-09-10T08:22:35Z
dc.date.issued 2019-06
dc.description.abstract The aim of this study was to use genome-wide SNP data to investigate phenotypic and genetic differences in resistance to Haemonchus contortus between resistant and susceptible South African Dohne Merino sheep. The participating farm (Wauldby) has a history of heavy H. contortus challenge and implemented a selection strategy for resistance to H. contortus in 2011. Faecal egg count (FEC), body condition scores (BCS) and Famacha© scores (FAM) were recorded annually on lambs from weaning in January until the end of June from 2011 to 2014. Animals with FAM scores of ≥ 2.5 or BCS scores < 1.5 were subjected to anthelmintic treatment and recorded as “Dosed” animals. Animals (196) were selected for genotyping based on EBV for FEC and classified into Case and Control groups on the basis of whether they were dosed or not. The Grootfontein Dohne Merino flock has never been subjected to selection for resistance to gastrointestinal parasites and 48 animals were selected on FEC for genotyping. DNA obtained from blood samples were genotyped using the Illumina® Ovine SNP50 BeadChip. Principal component analysis (PCA) resulted in four distinct genetic clusters, with the Grootfontein sheep population clustering separately. The Wauldby animals in Cluster 3 had significantly lower FEC and higher BCS than the animals in Clusters 2 and 4. FEC breeding values of 114 ± 97, -629 ± 84 and -2 ± 45 were recorded for PCA-based Genetic cluster 2, 3 and 4 animals, respectively. The majority (88%) of animals in Cluster 3 were the progeny of sires from the resistant line. The average number of runs of homozygosity (ROH) was 44, 46, 54 and 47 per animal for Clusters 1, 2, 3 and 4 respectively. The highest number of ROHs was found on chromosomes 1, 2, 3, 4, 6, 9 and 10, on which QTL for resistance traits have been identified previously. Sires in Genetic cluster 3 were highly resistant and can be used in a breeding program to develop H. contortus resistant sheep. The results indicated genetic variation in host resistance against H. contortus in the Wauldby flock and breeding for resistance against nematodes is feasible. en_ZA
dc.description.department Animal and Wildlife Sciences en_ZA
dc.description.embargo 2020-06-01
dc.description.librarian hj2019 en_ZA
dc.description.sponsorship The South African Agricultural Research Council and Red Meat Research and Development South Africa. en_ZA
dc.description.uri http://www.elsevier.com/locate/smallrumres en_ZA
dc.identifier.citation Dlamini, N.M., Visser, C., Snyman, M.A. et al. 2019, 'Genomic evaluation of resistance to Haemonchus contortus in a South African Dohne Merino flock', Small Ruminant Research, vol. 175, pp. 117-125. en_ZA
dc.identifier.issn 0921-4488 (print)
dc.identifier.issn 1879-0941 (online)
dc.identifier.other 10.1016/j.smallrumres.2019.04.020
dc.identifier.uri http://hdl.handle.net/2263/71304
dc.language.iso en en_ZA
dc.publisher Elsevier en_ZA
dc.rights © 2019 Elsevier B.V. All rights reserved. Notice : this is the author’s version of a work that was accepted for publication in Small Ruminant Research. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. A definitive version was subsequently published in Small Ruminant Research, vol. 175, pp. 117-125, 2019. doi : 10.1016/j.smallrumres.2019.04.020. en_ZA
dc.subject Famacha© scores (FAM) en_ZA
dc.subject Faecal egg count (FEC) en_ZA
dc.subject Body condition scores (BCS) en_ZA
dc.subject Gastrointestinal nematodes en_ZA
dc.subject Runs of homozygosity (ROH) en_ZA
dc.subject Principal component analysis (PCA) en_ZA
dc.subject South Africa (SA) en_ZA
dc.subject Dohne Merino flock en_ZA
dc.subject Gastrointestinal nematodes (GIN) en_ZA
dc.subject Haemonchus contortus en_ZA
dc.title Genomic evaluation of resistance to Haemonchus contortus in a South African Dohne Merino flock en_ZA
dc.type Postprint Article en_ZA


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