Disease & heat resistance

Evaluating cortisol-related signal as a potential indicator of heat stress response in Iberian pig selection programs: a simulation study

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Abstract

The improvement of pig resilience to climate change is gaining importance, as stressful environmental events are becoming increasingly frequent and negatively affecting animal welfare. The Iberian pig is an indigenous breed originating from the Iberian Peninsula, well adapted to its local harsh environment. Here, a cortisol-related metabolomic stress signal is considered a potential indicator of the physiological response to stress. To evaluate the potential impact of including this stress-related signal as a breeding objective in Iberian pig breeding programs, we conducted stochastic simulations using the Modular Breeding Program Simulator (MoBPS) framework in R. The study was fully simulation-based. Two breeding schemes were evaluated: a nucleus breeding programme based on data from Pig Improvement Company (PIC), and an extensive production system reflecting the national breeding program in Spain. The two breeding schemes differed in the definition of selection indices, sets of traits, and trait grouping across stages of the breeding cycle, reflecting contrasting breeding program structures, with parameter sets applied independently within each scheme. Selection strategies included phenotypic selection, pedigree-based BLUP, and single-step genomic BLUP (ssGBLUP) with different proportions of genotyped animals (10%, 25%, 50%, and 100%), combined with alternative population sizes (2000 sows and 500 boars vs. 500 sows and 125 boars) and selection intensities (10%, 20%, and 30% for sows combined with 5%, 10%, 20%, and 30% for boars). The simulations accounted for overlapping generations, age-structured cohorts, predefined mating designs, and linkage disequilibrium generated through historical recombination as implemented in MoBPS. Production and reproductive traits were modelled using programme-specific parameters from published studies or PIC data, whereas the cortisol-related metabolomic signal was modelled assuming a polygenic genetic architecture, with its heritability and phenotypic variance derived from Re-Livestock data. Because no studies reported genetic correlations between this stress-related signal and the other traits included in the simulations, these correlations were assumed to be zero. To reflect practical constraints associated with cortisol phenotyping, records for the cortisol-related signal were available only for a subset of animals (15% of both sexes), resulting in substantially lower recording intensity compared with routinely measured production and reproductive traits. Across scenarios, ssGBLUP generally resulted in greater genetic gain than phenotypic selection, while its advantage over pedigree-based BLUP depended on the proportion of genotyped animals. Including the cortisol-related signal in the selection index changed the response of this trait in the expected direction, mainly under pedigree-based BLUP and ssGBLUP, while having only a limited effect on the base production and reproductive breeding objective. This study provides a simulation-based framework for future Iberian pig breeding programs and highlights the potential of resilience-related traits to support sustainable genetic development. This research was funded by the European Union (grant no. 101059609).

Keywords: 2026

How to Cite:

Pycińska, N., Lewis, C., Herrero, J., Muñoz, M., García-Casco, J., Sell-Kubiak, E. & Pszczola, M., (2026) “Evaluating cortisol-related signal as a potential indicator of heat stress response in Iberian pig selection programs: a simulation study”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2285625. doi: https://doi.org/10.31274/wcgalp.23757

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