Genotypes identified by genome-wide association analyses influence yearling pulmonary arterial pressure and growth traits in Angus heifers from a high-altitude beef production system

Abstract

Reducing the prevalence of hypoxia-induced pulmonary hypertension (PH) remains a challenge to high-altitude beef production systems. Previous research and selection strategies have focused on the impact of bulls with PH in gain-test; however, little information is available on heifers that are typically developed in grazing systems. We hypothesized that indicator traits for PH in heifers are genomically associated with growth traits. The objectives of this study were to 1) identify SNP associated with yearling mean pulmonary arterial pressure (YPAP) and growth traits, 2) evaluate sequence variants common to YPAP and growth traits, and 3) identify underlying genes for QTL in Angus cattle. Yearling heifers (n = 1180) grazing in a high-altitude beef production system were measured for YPAP. Additionally, growth measures such as age of dam adjusted birth weight (BW), 205 d weaning weight (WW), 365 d yearling weight (YW), 365 d hip height (HH), and 160 d post-weaning gain (PWG) were also recorded. Isolated DNA from blood, hair, or blood card samples were analyzed using the Ilumina BovineSNP50 Beadchip. Genome-wide association analyses were conducted using an additive multi-locus mixed model with a 5% false discovery rate to account for multiple comparisons. Genotypes adjusted for FDR (P ≤ 1.00E−05; number of SNP) were associated with BW (2), YW (1), PWG (1), and HH (6), but no SNP were associated with YPAP or WW at this significance level. Associated SNP (P ≤ 1.00E−03; number of SNP) were identified for YPAP (37), BW (42), WW (31), YW (38), PWG (36), and HH (65). There was one SNP concordant with YPAP, YW, and HH, another with YPAP, YW, and PWG, and one SNP was concordant between YPAP and BW. Underlying genes within 1 kb of concordant SNP were SLC36A2 and CFAP58 and are involved in small amino acid transportation and cell cycle processes, respectively. Results suggested that 2 genomic regions may co-associate YPAP and growth traits. However, given these SNP accounted for <0.05 percentage of the genomic variance, selection for growth will have limited influence on YPAP and subsequently incidence of hypoxia-induced PH in beef heifers developed in grazing systems.