Puberty classifications in beef heifers are moderately to highly heritable and associated with candidate genes related to cyclicity and timing of puberty

Authors

Melanie K. Hess, University of Nebraska–Lincoln
Anteneh Mersha, University of Nebraska–Lincoln
Sadie S. Ference, University of Nebraska–Lincoln
Sarah R. Nafziger, University of Nebraska–Lincoln
Jessica A. Keane, University of Nebraska–Lincoln
Anna M. Fuller, University of Nebraska-LincolnFollow
Scott G. Kurz, University of Nebraska-LincolnFollow
Courtney M. Sutton, University of Nebraska–Lincoln
Matthew L. Spangler, University of Nebraska - LincolnFollow
Jessica Lynn Petersen, University of Nebraska - LincolnFollow
Andrea S. Cupp, University of Nebraska at LincolnFollow

Document Type

Article

Date of this Version

6-13-2024

Citation

Hess MK, Mersha A, Ference SS, Nafziger SR, Keane JA, Fuller AM, Kurz SG, Sutton CM, Spangler ML, Petersen JL and Cupp AS (2024), Puberty classifications in beef heifers are moderately to highly heritable and associated with candidate genes related to cyclicity and timing of puberty. Front. Genet. 15:1405456. doi: 10.3389/fgene.2024.1405456

Comments

Open access.

Abstract

Introduction: Pubertal attainment is critical to reproductive longevity in heifers. Previously, four heifer pubertal classifications were identified according to attainment of blood plasma progesterone concentrations > 1 ng/ml: 1) Early; 2) Typical; 3) Start-Stop; and 4) Non-Cycling. Early and Typical heifers initiated and maintained cyclicity, Start-Stop started and then stopped cyclicity and Non- Cycling never initiated cyclicity. Start-Stop heifers segregated into Start-Stop- Discontinuous (SSD) or Start-Stop-Start (SSS), with SSD having similar phenotypes to Non-Cycling and SSS to Typical heifers. We hypothesized that these pubertal classifications are heritable, and loci associated with pubertal classifications could be identified by genome wide association studies (GWAS).

Methods: Heifers (n = 532; 2017 – 2022) genotyped on the Illumina Bovine SNP50 v2 or GGP Bovine 100K SNP panels were used for variant component estimation and GWAS. Heritability was estimated using a univariate Bayesian animal model.

Results: When considering pubertal classifications: Early, Typical, SSS, SSD, and Non-Cycling, pubertal class was moderately heritable (0.38 ± 0.08). However, when heifers who initiated and maintained cyclicity were compared to those that did not cycle (Early+Typical vs. SSD+Non-Cycling) heritability was greater (0.59 ± 0.19). A GWAS did not identify single nucleotide polymorphisms (SNPs) significantly associated with pubertal classifications, indicating puberty is a polygenic trait. A candidate gene approach was used, which fitted SNPs within or nearby a set of 71 candidate genes previously associated with puberty, PCOS, cyclicity, regulation of hormone secretion, signal transduction, and methylation. Eight genes/regions were associated with pubertal classifications, and twentytwo genes/regions were associated with whether puberty was attained during the trial. Additionally, whole genome sequencing (WGS) data on 33 heifers were aligned to the reference genome (ARS-UCD1.2) to identify variants in FSHR, a gene critical to pubertal attainment. Fisher’s exact test determined if FSHR SNPs segregated by pubertal classification. Two FSHR SNPs that were not on the bovine SNP panel were selected for additional genotyping and analysis, and one was associated with pubertal classifications and whether they cycled during the trial.

Discussion: In summary, these pubertal classifications are moderately to highly heritable and polygenic. Consequently, genomic tools to inform selection/ management of replacement heifers would be useful if informed by SNPs associated with cyclicity and early pubertal attainment.