Sustainability & efficiency

Derivation of energy allocation coefficients to growth and exploration of its genetic background in American Angus cattle

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Abstract

Improving feed efficiency while maintaining resilience remains a central challenge in livestock breeding. Energy allocation theory provides a framework to interpret biological efficiency in terms of how animals partition available resources among competing physiological functions. However, direct quantification of individual energy allocation strategies from large-scale field data remains underdeveloped. Here, we defined an energy allocation coefficient to growth (α) as the proportion of net energy available beyond maintenance that an animal allocates to growth, and investigated its genetic background in American Angus cattle. Two complementary approaches were evaluated: (i) a two-step (TS) approach, in which α was derived as a log-transformed pseudo-phenotype from a bioenergetic framework and analyzed using linear animal models; and (ii) a one-step (OS) approach, in which empty-body gain was modeled as a nonlinear function of α, enabling joint estimation of breeding values and variance components. Genetic parameters were estimated using both pedigree- and genomic-based relationship matrices, and consistency between approaches was assessed. Genotype-by-environment (G×E) interactions across energy intake levels, and genetic relationships with feed efficiency and body composition traits were also examined. The α was moderately heritable (h² = 0.13-0.20), with strong consistency in breeding value rankings between approaches (Spearman ρ > 0.92; top-25% overlap > 81%). It showed favorable genetic correlations with growth and feed efficiency traits (average daily gain: 0.63; feed conversion ratio: −0.80; residual feed intake: −0.54; residual average daily gain: 0.61), while its weak association with dry matter intake (−0.14) suggests that α primarily reflects an intrinsic energy partitioning strategy rather than differences in absolute intake. Genetic correlations between α and body composition traits were generally low, with a slight tendency toward leaner deposition (fat thickness: −0.12 to −0.13) and near-zero correlations with ribeye area and intramuscular fat, implying minimal impact on muscularity or meat quality. High genetic correlations across low, medium, and high energy intake environments (0.91-0.98) indicated limited G×E interaction and largely consistent genetic control of α across nutritional conditions. The energy allocation coefficient to growth (α) is a heritable and biologically meaningful trait capturing how animals partition available energy toward growth, largely independent of feed intake level. Despite minor differences in variance estimates between approaches, the underlying genetic signal was robust, with the TS framework offering a practical and computationally tractable option for routine genetic evaluation. Its favorable genetic associations with efficiency traits and stability across energy environments support its potential as a complementary selection criterion to improve resource efficiency in beef cattle. Further work should explore relationships between α and health, longevity, and resilience traits to inform balanced and sustainable breeding programs.

Keywords: 2026

How to Cite:

Brito, L., Friggens, N., Garcia, A., Huang, Q., J. M. Rosa, G., Oliveria, H., Retallick, K., Santana, M. & Schinckel, A., (2026) “Derivation of energy allocation coefficients to growth and exploration of its genetic background in American Angus cattle”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2286176. doi: https://doi.org/10.31274/wcgalp.23870

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