Genome-wide assessment of runs of homozygosity to estimate inbreeding in a closed Nellore herd

• Published in: Livestock science 2024-10, Vol.288, p.105547, Article 105547
• Main Authors: Bittencourt, Angela, Egito, Andréa Alves do, Suniga, Paula Adas Pereira, Santiago, Gustavo Garcia, Santos, Rafael Monteiro dos, Cardoso, Eduardo Penteado, Verardo, Lucas Lima, Silva, Marcos Vinicius Gualberto Barbosa da, Toral, Fabio Luiz Buranelo
• Format: Article
• Language: English
• Subjects: Autozygosity; Bos indicus; Genomic inbreeding coefficients; Inbreeding; Selection; SNP
• ISSN: 1871-1413
• DOI: 10.1016/j.livsci.2024.105547

•Genotyping chips with 30 K markers are sufficient in detecting recent inbreeding events through runs of homozygosity.•Closed selection herds can maintain acceptable levels of inbreeding, since that mattings are conducted in a way that balances genetic variability and genetic progress.•The use of runs of homozygosity appears to be the optimal method for estimating inbreeding, as it provides information on haplotypes that are identical by descent.•A candidate gene (HTR1A) for docility identified in ROH islands is presented. The objective of this study was to compare the inbreeding coefficients estimated from pedigree data (FPED), traditionally used for internal monitoring by herds and breeding programs, with genomic estimates through the genomic relationship matrix (FGRM) and runs of homozygosity (FROH). Besides, we used the genotype data to obtain the linkage disequilibrium (LD), population effective size (Ne), runs of homozygosity (ROH) islands and functional analysis of the genes presented in ROH islands. Male calves and sires from a closed Nellore herd (Lemgruber line) were genotyped with the Z-chip v2 (Neogen, Lincoln, Nebraska, USA) that contains approximately 30 thousand SNP markers. After quality control, 1088 animals and 21,351 SNPs remained for analysis. Runs of homozygosity (ROH) segments were identified in all analyzed animals, with an average number of 57.93 and average length of 2.95 Mb. We observed a higher occurrence of ROH up to 9 Mb, suggesting a proper mating scheme, which corroborate with LD and Ne analysis results. Estimates of FPED, FGRM and FROH ranged from 0 to 0.2856, from 0.0705 to 0.3686 and from 0.0229 to 0.2762, respectively. Low to moderate correlations were observed between FPED and FGRM (0.17, P < 0.001); FPED and FROH (0.20, P < 0.001) and FGRM and FROH (0.92, P < 0.001). Nevertheless, considering our results we were successful in use runs of homozygosity for estimating autozygosity in a closed Nellore herd. Besides, from ROH islands, we were able to identify a candidate gene (HTR1A) for docility in this Nellore herd.