Genetic parameters for novel climatic resilience indicators derived from automatically-recorded vaginal temperature in lactating sows under heat stress conditions

Authors: WEN, HUI - Purdue University; Johnson, Jay; GLORIA, LEONARDO - Purdue University; ARAUJO, ANDRE - Purdue University; MASKAL, JACOB - Purdue University; HARTMAN, SHARLENE - Purdue University; DE CARVALHO, FELIPE - Purdue University; ROCHA, ARTUR - Purdue University; HUANG, YIJIAN - Smithfield Foods, Inc; TIEZZA, FRANCESCO - University Of Florence; MALTECCA, CHRISTIAN - North Carolina State University; SCHINCKEL, ALLAN - Purdue University; BRITO, LUIZ - Purdue University

Submitted to: Genetics Selection Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/6/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Heat stress has a reductive effect on swine welfare and performance metrics and decreases the economic sustainability of animal agriculture. As such, improving the ability of pigs to cope with heat stress challenges is of utmost importance to the U.S. and global swine industry. Genomic selection may be a viable tool to improve heat stress resilience in pigs. However, identifying phenotypes that can be easily collected on a large population of animals is necessary to develop genomic selection models that accurately predict heat stress resilience. Therefore, the study objective was to derive heat stress resilience indicators based on body temperature response to ambient temperature changes in lactating sows and estimate their variance components and genetic parameters. As a result of this project, we were able to identify a total of 15 heat stress resilience indicators that can be used to genomically predict heat stress tolerance in pigs. It is expected that these results will significantly contribute to the ability of swine producers to develop more heat stress resilient pigs that have better welfare and performance under heat stress conditions.

Technical Abstract: Background: Lactating sows are at an increased risk of suffering from heat stress (HS) due to their increased metabolic heat production during lactation and intensive selection for greater productive and reproductive performance. Longitudinal records of automatically-recorded vaginal temperature (TV) enables researchers to capture variations in sow core body temperature, which can then be used to develop new indicators of climatic resilience (CR) for breeding more resilient animals. Therefore, we derived 15 CR indicators based on TV in lactating sows and estimated their variance components and genetic parameters. Furthermore, we also investigated the relationship between these CR indicators and reproductive traits. Results: The heritability estimates for the 15 CR traits ranged from 0.001 ± <0.001 (SlopeDe: slope for decreased rate of TV) to 0.291 ± 0.047 (HSUB: sum of TV values below the HS threshold). The repeatability of CR indicators with multiple records ranged from 0.000 ± 0.000 (RAslope: logarithm transformed ratio of SlopeIn to SlopeDe) to 0.547 ± 0.142 (HSD: heat stress duration). Moderate to high positive genetic correlations (0.508 ± 0.056 to 0.990 ± 0.201) and Spearman correlations (0.431 to 1.000) of genomic estimated breeding values (GEBV) ranks were observed for HSD, Nor_medvar (Normalized median multiplies normalized variance), MaxTv (the highest TV of each measurement day for each individual), HSUA (the sum of TV values above the HS threshold), and HSUB. These five CR indicators showed low to moderate genetic correlation values with shoulder skin surface temperature (TSS, 0.139 ± 0.008 to 0.478 ± 0.048) and respiration rate (RR, 0.079 ± 0.011 to 0.502 ± 0.098). In addition to the genetic correlations between the five selected CR indicators and reproductive performance [Total number of piglets born alive (LB), total number of piglets born (TB), and number of pigs weaned (PW)] ranged from -0.733 to -0.175, -0.261 to 0.086, and -0.434 to -0.169, respectively. The top 100 individuals with the highest GEBV values (most heat sensitive) had higher (P < 0.05) skin surface temperature, RR, panting score (PS), and hair density (HD), but had lower (P-value?) mean body condition scores when compared to the bottom 100 individuals (most heat resilient). Conclusions: Most CR indicators evaluated are heritable with substantial additive genetic variance. Five CR indicators (HSD, MaxTv, HSUA, HSUB, Nor_medvar) have more similar underlying genetic mechanisms. Individuals displaying higher CR are more likely to exhibit better HS related physiological performance, larger body condition scores under hot conditions, and improved reproductive performance. These findings highlight the potential benefits of genetically selecting more heat-resilient individuals based on the CR indicators defined in this study.