Estimation & Prediction

Development of a multi-breed genomic prediction of a fertility index for tropically adapted beef bulls

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Abstract

The urgent need for agricultural systems to implement climate change adaptation strategies tailored to tropical environments highlights the importance of adopting sustainable bull breeding practices in beef cattle operations. We consider a population 6,063 bulls from six tropically adapted breeds with imputed genotypes for 680,758 single nucleotide polymorphisms (SNP), and phenotypes for ten fertility traits, including four observations on the bull (body weight, body condition score, scrotal circumference and sheath score) and six observations on the bull's semen (density, mass activity, motility, percentage of normal sperm, cytoplasmic droplets and middle-piece abnormalities). The breeds considered include Brahman (N=1,051), Tropical Composite (N=1,819), Santa Gertrudis (N=929), Droughtmaster (N=760), Ultra Black (N=844) and Belmont Tropical Composite (N=660). Earlier work examined genomic predictions and candidate functional variants for individual traits. In the current study, using principal component analysis (PCA) approaches, we propose combining the ten phenotypes into a single index, namely TBFi for Tropical Bull Fertility index. The first three principal components of the phenotypes accounted for 31.9%,17.9% and 12.1% of the total variation, respectively, while 90% of the total variation was captured by the first six principal components. For instance, the first principal component (PC1) contained positive loadings for all traits except sheath score (loading = -0.127), cytoplasmic droplets (-0.365) and middle-piece abnormalities (-0.282). Therefore, PC1 is offered as a satisfactory TBFi candidate. Across the 6,063 bulls, the mean TBFi was 0.000 and ranged from -105.42 to 92.51, and with 95.5% of records within 2 SD from the mean. After genomic analyses, estimates of heritability, and genetic variance were 0.213 ± 0.021 and 131.28 ± 12.99, respectively. Further research is warranted to examine the accuracy, bias and dispersion of the resulting genomic predictions for TBFi using the LR method. We anticipate the industry adoption of genomic predictions for TBFi will enable the early in-life selection of bulls, supporting genetic improvement strategies currently taking place within tropical beef production systems.

Keywords: 2026

How to Cite:

Reverter, A., Alexandre, P. & Porto-Neto, L., (2026) “Development of a multi-breed genomic prediction of a fertility index for tropically adapted beef bulls”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2286276. doi: https://doi.org/10.31274/wcgalp.23902

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