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Abstract
A total of 184 Djallonké lambs from Burkina Faso with phenotypes for packed-cell volume (PCV), log-transformed fecal egg count (lnFEC), and FAffa MAlan CHArt (FAMACHA©) eye scores were typed with the OvineSNP50 BeadChip of Illumina to contribute to the knowledge of the genetic basis of gastrointestinal (GIN) parasite resistance in sheep. Association analysis identified a total of 22 single-nucleotide polymorphisms (SNPs) related with PCV (6 SNPs), lnFEC (7), and FAMACHA scores (9) distributed among 14 Ovis aries chromosomes (OAR). The identified SNPs accounted for 18.76 % of the phenotypic variance for PCV, 21.24 % for lnFEC, and 34.38 % for FAMACHA scores. Analyses pointed out the importance of OAR2 for PCV, OAR3 for FAMACHA scores, and OAR6 for lnFEC. The 125 kb regions surrounding the identified SNPs overlapped with seven previously reported quantitative trait loci (QTLs) for the traits analyzed in the current work. The only chromosome harboring markers associated with the three traits studied was OAR2. In agreement with the literature, two different chromosomal areas on OAR2 can play a major role in the traits studied. Gene-annotation enrichment analysis allowed us to identify a total of 34 potential candidate genes for PCV (6 genes), lnFEC (4), and FAMACHA scores (24). Annotation analysis allowed us to identify one functional term cluster with a significant enrichment score (1.302). The cluster included five genes (TRIB3, CDK4, CSNK2A1, MARK1, and SPATA5) involved in immunity-related and cell-proliferation processes. Furthermore, this research suggests that the MBL2 gene can underlie a previously reported QTL for immunoglobulin A levels on OAR22 and confirms the importance of genes involved in growth and size (such as the ADAMTS17 gene on OAR18) for GIN resistance traits. Since association studies for the ascertainment of the genetic basis of GIN resistance may be affected by genotype–environment interactions, obtaining information from local sheep populations managed in harsh environments contributes to the identification of novel genomic areas of functional importance for GIN resistance for that trait.
Highlights
Gastrointestinal (GIN) parasite infections are a major obstacle for sustainable small-ruminant production due to their detrimental effects upon food digestion and utilization, skeletal and muscular development, fertility, wool and milk production, mortality rates, and antiparasitic expenditure (Jackson et al, 2009)
Since association studies for the ascertainment of the genetic basis of GIN resistance may be affected by genotype–environment interactions, obtaining information from local sheep populations managed in harsh environments contributes to the identification of novel genomic areas of functional importance for GIN resistance for that trait
Mean of the estimated breeding values (EBVs) estimated for packed-cell volume (PCV), log-transformed fecal egg count (lnFEC), and FAMACHA scores were 1.430 (1.126), 0.278 (0.378), and 0.189 (0.408), respectively
Summary
Gastrointestinal (GIN) parasite infections are a major obstacle for sustainable small-ruminant production due to their detrimental effects upon food digestion and utilization, skeletal and muscular development, fertility, wool and milk production, mortality rates, and antiparasitic expenditure (Jackson et al, 2009). Most heritability estimates reported for traits related to GIN resistance varied from moderate to low (Safari et al, 2005; Gutiérrez-Gil et al, 2010; Goldberg et al, 2012). Selection for such a complex phenotype is costly and time consuming. These requirements are not frequently met in the small-ruminant industry, in low-income smallholder systems which are predominant in developing countries (Zvinorova et al, 2016)
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