Abstract
BackgroundHeat 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.ResultsA 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.ConclusionsGenetic 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.
Highlights
Heat stress has a negative impact on pork production, during the grow-finish phase
For Yorkshire and Duroc sired pigs, feeding activity increased as temperature humidity index (THI) increased, while the opposite trend was observed for Landrace sired pigs
An interesting observation in the current study was that the difference in feeding activity between barrows and gilts increased with increasing temperatures for all sire breed by THI categories except Landrace sired pigs in the Emergency category
Summary
Heat stress has a negative impact on pork production, 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. In the USA, economic losses due to heat stress are estimated at $300 million per year, of which a majority occur during the grow-finish phase [1]. Production losses due to heat stress result from decreased growth of market hogs, reduced feed intake, and mortality [2,3,4]. Swine feeding behavioural patterns change as temperature increases. Pigs spend less time eating and more time lying down during high temperatures [5, 6] and change eating behaviour, mealtime, and meal size [5, 7]. Pigs have a thermal comfort zone in which they are most productive, which depends on several factors, including sex, genetics, relative humidity, and velocity of ambient air [9, 10]
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