Genomic regions and pathways associated with gastrointestinal parasites resistance in Santa Inês breed adapted to tropical climate

Abstract

BackgroundThe aim of this study was to estimate variance components and to identify genomic regions and pathways associated with resistance to gastrointestinal parasites, particularly Haemonchus contortus, in a breed of sheep adapted to tropical climate. Phenotypes evaluations were performed to verify resistance to gastrointestinal parasites, and were divided into two categories: i) farm phenotypes, assessing body condition score (BCS), degree of anemia assessed by the famacha chart (FAM), fur score (FS) and feces consistency (FC); and ii) lab phenotypes, comprising blood analyses for hematocrit (HCT), white blood cell count (WBC), red blood cell count (RBC), hemoglobin (HGB), platelets (PLT) and transformed (log10) egg per gram of feces (EPGlog). A total of 576 animals were genotyped with the Ovine SNP12k BeadChip (Illumina, Inc.), that contains 12,785 bialleleic SNP markers. The variance components were estimated using a single trait model by single step genomic BLUP procedure.ResultsThe overall linkage disequilibrium (LD) mean between pairs of markers measured by r 2 was 0.23. The overall LD mean between markers considering windows up to 10 Mb was 0.07. The mean LD between adjacent SNPs across autosomes ranged from 0.02 to 0.10. Heritability estimates were low for EPGlog (0.11), moderate for RBC (0.18), PLT (0.17) HCT (0.20), HGB (0.16) and WBC (0.22), and high for FAM (0.35). A total of 22, 21, 23, 20, 26, 25 and 23 windows for EPGlog for FAM, WBC, RBC, PLT, HCT and HGB traits were identified, respectively. Among the associated windows, 10 were shown to be common to HCT and HGB traits on OAR1, OAR2, OAR3, OAR5, OAR8 and OAR15.ConclusionThe traits indicating gastrointestinal parasites resistance presented an adequate genetic variability to respond to selection in Santa Inês breed, and it is expected a higher genetic gain for FAM trait when compared to the others. The level of LD estimated for markers separated by less than 1 Mb indicated that the Ovine SNP12k BeadChip might be a suitable tool for identifying genomic regions associated with traits related to gastrointestinal parasite resistance. Several candidate genes related to immune system development and activation, inflammatory response, regulation of lymphocytes and leukocytes proliferation were found. These genes may help in the selection of animals with higher resistance to parasites.Electronic supplementary materialThe online version of this article (doi:10.1186/s40104-017-0190-4) contains supplementary material, which is available to authorized users.

Genetic parameter estimates for gastrointestinal nematode parasite resistance and maternal efficiency indicator traits in Santa Inês breed

“…The identification of genomic regions that affect both parasite resistance and ME indicator traits may become a relevant tool to understand and elucidated the genetics mechanism that improves the resistance of Santa Ines sheep breed, given the expensive and difficult nature of collecting phenotypic records. In this sense, Berton et al () using the same data set as in the present study identified two common genomic regions between FMC and EPG log , suggesting that these genomic regions had pleiotropic effect for FMC and EPG log and endorses the genetic correlation between them. Furthermore, Berton et al () and Amorim et al () reported genomic harbouring genes related with immune response and growth regulation for gastrointestinal parasite resistance and ME indicator traits.…”

“…The Santa Inês sheep breed, an American hair breed, displays higher resistance to gastrointestinal nematode infections than the European sheep breeds (Amarante et al, ; Bricarello et al, ; Costa et al, ), and it has higher survivability in harsh environments with high infestation of gastrointestinal nematode larvae (Bricarello et al, ; Costa et al, ). Previous studies indicated that selection for gastrointestinal nematode parasite resistance is feasible in sheep production, since the heritability estimates for FMC and EPG ranged from 0.35 ± 0.11 to 0.55 ± 0.2 and from 0.11 ± 0.08 to 0.38 ± 0.04, respectively (Berton et al, ; Bisset et al, ; Karlsson & Greeff, ; Mcewan, ; Pickering et al, ; Woolaston & Windon, ).…”

Can the strategies for endoparasite control affect the productivity of lamb production systems on pastures?

“…According to Saddiqi et al (2011), the ability of a sheep to acquire immunity and express resistance varies substantially among and within breeds. Besides, given that there is some heritability of resistance to gastrointestinal parasites, the FMC scores indicates that selection process is possible in breeding programs (Berton et al, 2017). Selective strategies are based on phenotypic parameters that are used to select animals more resilient to endoparasites, which is not possible when a prophylactic strategy is applied to the entire flock (Molento et al, 2004).…”

Advances in molecular genetic techniques applied to selection for litter size in goats (Capra hircus): a review

“…Several studies of GWAS have already been carried out on some species of domestic animals, such as dairy cattle (Ismail et al 2017), beef cattle (Santiago et al 2017), swine (Van Son et al 2017), and sheep (Berton et al 2017). Currently, there are various GWAS in goats.…”