​​GENOMIC STUDIES OF NOVEL BEHAVIOR TRAITS IN LACTATING SOWS AND THEIR RELATIONSHIP TO HEAT STRESS RESILIENCE AND MATERNAL PERFORMANCE​
Creators: name: Hartman, Sharlene Olivette
Publisher: name: Purdue University Graduate School
Year: 2024
Subjects: classificationCode: 300305
subject: Animal reproduction and breeding
classificationCode: 300306
subject: Animal welfare
classificationCode: 300307
subject: Environmental studies in animal production

description: Heat stress is one of the leading welfare concerns for modern swine production globally. Swine are especially susceptible as the species has inactive sudoriferous glands and, as a result, these animals thermoregulate mainly through behaviors such as wallowing and rooting up cooler patches of ground. In commercial settings, access to open ground or wallowing pits would present a threat to the animals’ health in the form of a vector for diseases and parasites. This puts aspects of swine welfare in direct conflict with one another, while public legislature and consumer pressures increasingly call for approaches to animal welfare that encompass all aspects of welfare to be considered. Efforts towards improved welfare are also crucial to the environmental and economical sustainability for producers and consumers. Previous genetic selection tactics used in swine herds focused intensely on a few traits and have led to modern animals being highly productive but also more environmentally sensitive. Intensely selected animals have energy margins that are narrower and more devoted to higher production leaving less accommodations for resilience in moments of stress. Since swine behaviorally thermoregulate, the use of behavior studies combined with those of genetics is one possible way to effectively identify heritable aspects of climatic resilience into future herds while still improving production traits. The primary objectives of this thesis were to develop an ethogram that can be used to base phenotypes of behavior; calculate the variance components of the behavior traits; correlate these components with those of maternal productivity and heat tolerance; and finally explore the genetic background of the behavior traits based on the identification of genomic markers significantly associated with them. Data was collected on 1,678 Landrace × Large White sows from a commercial swine herd in North Carolina. The data comprised information on climatic factors, litter performance, and behavior during a standardized human handling procedure in the summer of 2021. These animals were genotyped using the PorcineSNP50K Bead Chip (Illumina, San Diego, CA, USA). These studies describe the development of an ethogram for use on lactating sows in a commercial setting in order to create the novel behavior traits of Responsiveness Score (RS), Vocalization Score (VS), and Shave Time (ST). The genetic variance components were then estimated, and heritabilities found to be 0.17 ± 0.05 for RS, 0.15 ± 0.05 for VS, and 0.10 ± 0.05. These novel behavior traits had low genetic correlations with traits of maternal performance and heat stress resilience. Genome-wide association studies were then performed, and 19 genomic markers were significantly associated with the three behavior traits. However, only one region located on chromosome 3 harbors a candidate gene that may play a role in heat stress resilience. Although the novel behavior traits explored in this study are heritable, they were not found to be viable indicator traits for heat stress resilience due to their low genetic correlations with direct indicators of heat tolerance in lactating sows. It is important that additional phenotypic records of behaviors related to welfare are generated in the future to better map their polygenic nature.