Definition and Genetic Parameters Estimation for Climatic Resilience Indicators Derived from Longitudinal Vaginal Temperature Records in Lactating Sows Under Heat Stress Conditions

Abstract Climatic resilience (CR) can be defined as the ability of an animal to maintain euthermia under thermally stressful conditions. However, CR based on longitudinal physiological variables has not been included in current swine genetic selection schemes. This is the first study deriving novel CR indicators using automatically recorded vaginal temperatures (TV) and estimating genetic parameters for them. Therefore, the study objectives were to: 1) derive novel indicators of CR based on automatically recorded vaginal temperature (TV); and 2) estimate (co)variance components and genetic parameters for these indicators. TV of 1,381 lactating sows (parities 2 to 7; Landrace × Large White) were measured automatically every 10 minutes from June 5th, 2021 to July 30th, 2021 using a vaginally implanted thermochron data recorder. A total of 1,639 F1 (Landrace x Large White) sows within the studied population were genotyped using the PorcineSNP50K Bead Chip. A total of 18 HS indicators derived from Tv, their definitions, heritability estimates, and mean genomic estimated breeding value (GEBV) accuracies are shown in Table 1. Multi-trait animal models were fitted for estimating the (co)variance components, considering the effects of week of data collection, parity, and location (barn and room within barn) as fixed. Heritability estimates for these resilience traits ranged from 0.0004 ± 7.16E-6 (SlopeDe) to 0.291 ± 0.047 (HSAB). Most traits derived directly from vaginal temperature (e.g., Duration: 0.201 ± 0.033, MaxTv: 0.203 ± 0.032) are moderately heritable with substantial additive genetic variance. Besides, LnVar(Med) that is derived from the deviation between the real and predicted value had moderate heritability (0.196 ± 0.041) and high mean GEBV accuracy (0.616 ± 0.042). The indicators defined based on the slope of Tv and time had low heritability estimates, which are close to zero, and low mean GEBV accuracy (0.106 ± 0.050 – 0.337 ± 0.065). Among all the CR indicators, Duration, MaxTv, Nor_medvar, Nor_avevar, HSAA, and HSAB outperformed the other indicators with moderate heritability estimates and high average GEBV accuracies. Genetic correlations were estimated among the six indicators with moderate heritability and high mean GEBV accuracy. Moderate to high positive genetic correlations (0.508 ± 0.034 to 0.992 ± 0.025) were estimated among Duration, MaxTv, Nor_medvar, HSAB, and HSAA. LnVar(Med) showed low negative genetic correlations (-0.218 ± 0.028 to -0.039 ± 0.018) with the traits Duration, MaxTv, HSAA, and HSAB, except with Nor_medvar, which was positive (0.156 ± 0.022). Thus, Duration, LnVar(Med), MaxTv, Nor_medvar, HSAB, and HSAA might be promising CR indicator and contribute toward improving lactating sows’ resilience to thermal stress through genetic selection. New studies about the relationship between these new indicators and other economic important traits in pigs are required before including them in selection indexes.