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. 2023 Sep 20;55(1):65.
doi: 10.1186/s12711-023-00842-x.

Genetic parameters for automatically-measured vaginal temperature, respiration efficiency, and other thermotolerance indicators measured on lactating sows under heat stress conditions

Pedro H F Freitas  1 , Jay S Johnson  2 , Hui Wen  1 , Jacob M Maskal  1 , Francesco Tiezzi  3   4 , Christian Maltecca  3 , Yijian Huang  5 , Ashley E DeDecker  6 , Allan P Schinckel  1 , Luiz F Brito  7
Affiliations

Genetic parameters for automatically-measured vaginal temperature, respiration efficiency, and other thermotolerance indicators measured on lactating sows under heat stress conditions

Pedro H F Freitas et al. Genet Sel Evol. .

Abstract

Background: Genetic selection based on direct indicators of heat stress could capture additional mechanisms that are involved in heat stress response and enable more accurate selection for more heat-tolerant individuals. Therefore, the main objectives of this study were to estimate genetic parameters for various heat stress indicators in a commercial population of Landrace × Large White lactating sows measured under heat stress conditions. The main indicators evaluated were: skin surface temperatures (SST), automatically-recorded vaginal temperature (TV), respiration rate (RR), panting score (PS), body condition score (BCS), hair density (HD), body size (BS), ear size, and respiration efficiency (Reff).

Results: Traits based on TV presented moderate heritability estimates, ranging from 0.15 ± 0.02 to 0.29 ± 0.05. Low heritability estimates were found for SST traits (from 0.04 ± 0.01 to 0.06 ± 0.01), RR (0.06 ± 0.01), PS (0.05 0.01), and Reff (0.03 ± 0.01). Moderate to high heritability values were estimated for BCS (0.29 ± 0.04 for caliper measurements and 0.25 ± 0.04 for visual assessments), HD (0.25 ± 0.05), BS (0.33 ± 0.05), ear area (EA; 0.40 ± 0.09), and ear length (EL; 0.32 ± 0.07). High genetic correlations were estimated among SST traits (> 0.78) and among TV traits (> 0.75). Similarly, high genetic correlations were also estimated for RR with PS (0.87 ± 0.02), with BCS measures (0.92 ± 0.04), and with ear measures (0.95 ± 0.03). Low to moderate positive genetic correlations were estimated between SST and TV (from 0.25 ± 0.04 to 0.76 ± 0.07). Low genetic correlations were estimated between TV and BCS (from - 0.01 ± 0.08 to 0.06 ± 0.07). Respiration efficiency was estimated to be positively and moderately correlated with RR (0.36 ± 0.04), PS (0.56 ± 0.03), and BCS (0.56 ± 0.05 for caliper measurements and 0.50 ± 0.05 for the visual assessments). All other trait combinations were lowly genetically correlated.

Conclusions: A comprehensive landscape of heritabilities and genetic correlations for various thermotolerance indicators in lactating sows were estimated. All traits evaluated are under genetic control and heritable, with different magnitudes, indicating that genetic progress is possible for all of them. The genetic correlation estimates provide evidence for the complex relationships between these traits and confirm the importance of a sub-index of thermotolerance traits to improve heat tolerance in pigs.

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Conflict of interest statement

YH and AD were employed by Smithfield Foods. The remaining authors declare that the research was conducted without any commercial or financial relationships that could be construed as a potential competing interests. The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Scheme representing the subsets for vaginal temperature measures. Graphic representation of all datasets derived from the automatically-measured vaginal temperature. TVall: corresponds to whole data measured every 10 min; TV4days: 4 measurements at 8:00, 12:00, 16:00, and 20:00 h during the 4 days; TV8h. TV12h, TV16h, TV20h: hourly daily measure for the 4 collection days at 8:00, 12:00, 16:00, and 20:00 h, respectively; TV8hS. TV12hS, TV16hS, TV20hS: single record day measured on the first day of collection at 8:00, 12:00, 16:00, and 20:00 h, respectively
See this image and copyright information in PMC

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