|CROSS, A - South Dakota State University|
|CASSADY, J - South Dakota State University|
Submitted to: Genetics Selection Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/26/2018
Publication Date: 3/25/2018
Citation: Cross, A.J., Keel, B.N., Brown-Brandl, T.M., Cassady, J.P., Rohrer, G.A. 2018. Genome-wide association of changes in swine feeding behaviour due to heat stress. Genetics Selection Evolution. 50:11. https://doi.org/10.1186/s12711-018-0382-1.
Interpretive Summary: Heat stress negatively impacts pork production, particularly during the grow-finish phase. As temperatures increase, a pig’s feeding behavior changes to decrease heat production. Genetic markers associated with heat stress could be used to select and breed for more heat resilient pigs. Scientists with USDA Agricultural Research Service in Clay Center, NE and South Dakota State University conducted a study to identify genetic markers associated with a pig’s response to heat stress. Pig feeding behaviour was electronically monitored throughout the study. Changes in feeding behaviour during different temperature-humidity index (THI) categories (normal, alert, danger or emergency) were studied to determine which pigs were unaffected by higher THI versus pigs that were severely affected by increased THI. Several interesting results were identified in these analyses. First, many regions of the genome identified contained a class of genes coding for heat shock proteins, which help protect stressed cells. Other regions identified contained genes regulating sensory perception, such as response to a stimulus or odor. Another gene family detected impacts sensory perception to heat. Genetic markers identified in this study may enable genetic selection for improved performance during increased temperatures. Selection for heat tolerant pigs would lead to increased production efficiency during summer months in U.S. commercial production and improved animal well-being.
Technical Abstract: Background: Heat stress has a negative impact on pork production, particularly during the grow-finish phase. As temperature increases, feeding behaviour changes in order for pigs to decrease heat production. The objective of this study was to identify genetic markers associated with changes in feeding behaviour due to heat stress. Feeding data were collected on 1154 grow-finish pigs using an electronic feeding system from July 2011 to March 2016. In this study, days were classified based on the maximum temperature humidity index (THI) during the day as “Normal” (< 23.33 °C), “Alert” (23.33 °C = × < 26.11 °C), “Danger” (26.11 °C = × < 28.88 °C), and “Emergency” (= 28.88 °C). Six hundred and eighty-one pigs that experienced more than one THI category were genotyped using a variety of SNP platforms, with final genotypes imputed to approximately 60,000 markers. Results: A genome-wide association study (GWAS) for change in feeding behaviour between each pair of THI categories (six pairs) was conducted. Estimates of heritability for differences in feeding activity between each of the THI categories were low (0.02 ± 0.03) to moderate (0.21 ± 0.04). Sixty-six associations which explained more than 1% of the genomic variation for a trait were detected across the six GWAS, with the smallest number of associations detected in comparisons with Emergency THI. Gene ontology enrichment analysis showed that biological processes related to immune response and function were over-represented among the genes located in these regions. Conclusions: Genetic differences exist for changes in feeding behaviour induced by elevated ambient temperatures in grow-finish pigs. Selection for heat-tolerant grow-finish pigs should improve production efficiency during warm months in commercial production. Genetic variation in heat shock, stress response and immune function genes may be responsible for the observed differences in performance during heat stress events.