ABSTRACT.- Selection of genetically resistant animals is one alternative to reduce the negative impact of gastrointestinal nematodes (GIN) on sheep production. The aim of this study was to identify genomic regions associated with GIN resistance in Corriedale sheep by single-step genome-wide association studies (ssGWAS) using 170, 507 and 50K single nucleotide polymorphisms (SNPs). Analysis included 19,547 lambs with faecal egg counts (FEC) records, a pedigree file of 40,056 animals and 454, 711 and 383 genotypes from 170, 507 and 50K SNPs, respectively.

ABSTRACT.- Context:Residual feed intake is a relevant trait for beef cattle, given the positive impact on reducing feeding costs and greenhouse gas emissions. The lack of large databases is a restriction when estimating accurate genetic parameters for dry matter intake (DMI) and residual feed intake (RFI), and combining different data sets could be an alternative to increase the amount of data and achieve better estimations.

ABSTRACT.- Single-step genomic BLUP (ssGBLUP) relies on the combination of the genomic ((Formula presented.)) and pedigree relationship matrices for all ((Formula presented.)) and genotyped ((Formula presented.)) animals. The procedure ensures (Formula presented.) and (Formula presented.) are compatible so that both matrices refer to the same genetic base (?tuning?). Then (Formula presented.) is combined with a proportion of (Formula presented.) (?blending?) to avoid singularity problems and to account for the polygenic component not accounted for by markers.