Beef cattle

Structural Soundness Matters: Genomic Evaluation of Functional Morphology in Nellore Cattle

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Abstract

Morphological defects can compromise mobility, welfare, and longevity in beef cattle, particularly in grazing systems where structural soundness and thermoregulation are essential for reproductive and economic performance. Although these traits directly affect functionality, they have rarely been included in large-scale genetic evaluations. This study aimed to quantify the prevalence, estimate genetic parameters, and describe the genetic relationships among five morphological defects in Nellore cattle using single-trait threshold animal models. Genomic breeding values were expressed on the probability scale to improve biological interpretation and communication of selection responses. Phenotypic records from 182,964 Nellore animals evaluated between 1998 and 2021 in the DeltaGen® breeding program were analyzed for five traits: feet and legs malformations, chamfer, hump, jaw defects, and skin depigmentation. All defects were recorded as binary traits using standardized field-scoring procedures performed by trained technicians. Pedigrees from 1,192,464 animals and genotypes (imputed to 777K SNPs) from 24,562 individuals were used. Variance components were estimated by Bayesian inference using the GIBBSF90+ software, and heritabilities estimated on the liability scale were converted to the observed scale for interpretation. Defect prevalence ranged from 4.23% for jaw defects to 7.44% for feet and legs malformations, with intermediate values for chamfer (5.05%), hump (5.59%), and depigmentation (6.18%). Heritability estimates on the observed scale ranged from 0.04 to 0.12, confirming the presence of additive genetic variance that can be exploited in selection programs. The highest heritability estimate was obtained for depigmentation (0.12), followed by hump (0.08), feet and legs malformations (0.06), jaw defects (0.05), and chamfer (0.04). Genetic correlations based on genomic breeding values revealed relationships of moderate magnitude among structural defects: feet and legs malformations with chamfer (0.39), feet and legs malformation with jaw defects (0.38), and chamfer with hump (0.53).These correlations suggest shared genetic control influencing skeletal conformation and body balance. In contrast, depigmentation showed weak correlations with the structural traits, below 0.22, supporting the hypothesis that independent biological mechanisms govern pigmentation loss. Transforming genomic breeding values from the liability to the probability scale allowed the expression of genetic merit in intuitive probability units, improving interpretability for breeders and enabling consistent comparison across traits with different prevalence levels. The probability scale provides a direct measure of expected incidence, facilitating the identification of animals with reduced likelihood of morphological defects and enhancing the practical use of genomic evaluations for binary traits. These results demonstrate that morphological defects in Nellore cattle are heritable and genetically structured traits that can be effectively incorporated into multi-trait genomic evaluations. Including them as auxiliary traits in selection indices can improve structural soundness, environmental adaptability, and animal welfare without compromising selection efficiency for production and reproduction.

Keywords: 2026

How to Cite:

Campos, M., Costa, R., Mulim, H., Hidalgo, J. & Oliveira, E., (2026) “Structural Soundness Matters: Genomic Evaluation of Functional Morphology in Nellore Cattle”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2284317. doi: https://doi.org/10.31274/wcgalp.23564

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