139 Genomic-Based Genetic Parameters of Behavioral Ethogram Traits in Lactating Sows Under Heat Stress Conditions and Their Relationship with Direct Indicators of Heat Tolerance
Authors: Johnson Jay S , Pedrosa Victor B , Schinckel Allan P , Marchant Jeremy N , Gloria Leonardo Siqueira 
Published: November 2023

Abstract
Increased global temperatures pose challenges to livestock agriculture. Domestic swine are particularly sensitive to hotter environments due to their inability to sweat, litter bearing nature, difficulty in expressing natural cooling behaviors, and intense genetic selection for production traits. Since animal welfare is central to livestock production as a matter vital to efficiency as much as ethics, developing novel traits that may be genetically related to heat tolerance may assist in improving and sustaining animal welfare. The objective of this study was to develop novel traits of behavior using an ethogram designed for efficiency in production settings, estimate the variance components, and correlate these traits with indicators of heat tolerance and maternal ability. This study considered 1,312 individual Landrace-Large White cross production sows between 6 and 19 days of lactation. Animals were housed in farrowing crates in a commercial setting in southern North Carolina in June and July of 2021, an environment susceptible to potential heat stress. These sows were subjected to a standardized procedure involving a person removing hair from both hips using an electric clipper while an observer was positioned in front of the sow to record behaviors. Scores were later applied to the variations in behavior both for changes in positions and types of vocalizations displayed by the animals during handling. Genotypes were obtained from hair follicles and captured by a 50K porcine SNP panel. Variance components for novel behavior traits were obtained using the BLUPF90+ programs and genomic relationship matrix to estimate genetic correlations of behavior with several indicators of heat tolerance and maternal ability. Heritabilities for behavior traits ranged from 0.131 for vocalization score to 0.072 for shaving time, while heritabilities for heat tolerance and maternal ability ranged from 0.15 to 0.03 for vaginal temperature and respiration efficiency, respectively. The maternal ability traits were based on the single current litter and had the lowest heritabilities ranging from 0.101 to 0.04 for number born alive and number of mummies, respectively. High and positive genetic correlations indicate a potential for coupled selection for both fewer mummified piglets and a greater number of liveborn using the behavior trait of vocalization score. These correlations between favorable maternal traits and behavior traits suggest the potential that one or more complex biological pathways exist that share relevancy between these traits. However, genetic correlations between the behavior traits and heat tolerance indicators were low to negligible, most with a magnitude falling below 0.10, revealing the need for other traits to be used as selection parameters for heat tolerance. Further studies may be able to capture additional environmental effects to improve models of behavior and create indirect measures more obtainable than direct measures of heat tolerance.