2026/03/11 by G.A. Oliveira, H.R. Oliveira, P. Fonseca +5 · 1 voice
Biochemistry, Genetics and Molecular Biology · Agricultural and Biological Sciences · #Genetic and phenotypic traits in livestock #Genetic Mapping and Diversity in Plants and Animals #Reproductive Physiology in Livestock
paper · pdf · doi:10.3168/jds.2025-27731
openalex publication_date 2026/03/11 · openalex created_date 2026/03/12 · openalex updated_date 2026/07/31
Timed artificial insemination (TAI) protocols have revolutionized reproductive management in dairy cattle, but their interaction with genetic factors affecting fertility traits remains poorly understood. This study was performed to investigate whether TAI protocols influence the genetic architecture of fertility traits compared with traditional heat detection (HD) systems. The dataset included 3,842 reproductive management protocol descriptions, classified as either TAI (2,002 records) or HD (1,840 records), with a final dataset with records from 90,298 first lactation cows. Genotypic data included 6,985 cows with records for first service to conception (FSTC) and days open (DO), and 7,220 cows with records for calving to first service (CTFS). After quality control, 44,819 SNP markers were retained for analysis. Variance components were estimated using a Bayesian single-step GBLUP multiple-trait animal model including milk yield. Heritabilities were consistently low across all fertility traits and reproductive management scenarios, ranging from 0.01 (95% highest posterior density [HPD]: 0.006 to 0.011; CTFS under TAI) to 0.04 (95% HPD: 0.035 to 0.044; DO under TAI). Importantly, genetic correlations between the same trait under HD and TAI were moderate to high but significantly less than unity: 0.74 ± 0.04 for FSTC, 0.89 ± 0.03 for CTFS, and 0.91 ± 0.01 for DO. Genome-wide association studies identified different associations depending on reproductive management systems. Functional annotation revealed 53 protein-coding genes within ±100 kb of significant SNPs, with distinct candidate genes identified for TAI and HD. In addition, QTL enrichment analysis demonstrated that traits under HD candidate regions were associated with broader functional categories, including milk production, reproduction, and exterior traits, whereas traits under TAI showed enrichment primarily for health-related traits. This study provides an empirical comparison of genetic parameters for fertility traits in dairy cattle under both TAI and traditional HD systems using large-scale real-world data. Our findings suggest that TAI influences the expression of genetic variation underlying reproductive traits, emphasizing the importance of accounting for reproductive management in genetic evaluations. This could be achieved by treating fertility under different systems as genetically distinct but correlated traits in multiple-trait models.