A large-effect locus on chromosome 4 underlies circadian feeding rhythmicity in pigs

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Abstract Circadian feeding rhythmicity reflects the distribution of feed intake across the daily 24-hour cycle. Regular feeding-fasting cycles play an important role in regulating metabolism and maintaining health, but endogenous and environmental factors can disrupt the normal circadian pattern of feed intake. Here, we quantified hourly feed intake in 3,470 Swiss Landrace and 15,181 Swiss Large White pigs using 40.5 million records from automated feeding systems. We used the proportion of days exhibiting a significant feeding rhythm after wavelet analysis to investigate variation in circadian feeding organization. Circadian feeding rhythmicity was influenced by sex and age, with higher rhythmicity observed in females and older animals. Variance components analysis revealed a strong additive genetic contribution and a high heritability (h² = 0.53-0.57). Pigs with higher circadian feeding rhythmicity had reduced nocturnal intake, improved feed conversion ratio, and lower day-to-day variability in feed intake, suggesting improved feed efficiency and resilience. Genome-wide association testing of 15.7 and 23.1 million imputed sequence variants identified a QTL on chromosome 4 explaining 5.3% and 2.9% of the phenotypic variance of circadian feeding rhythmicity in Swiss Landrace and Swiss Large White pigs, respectively. The QTL overlaps OPRK1 and NPBWR1 , two genes implicated in the regulation of feeding behavior, reward and energy homeostasis. Collectively, our findings establish circadian feeding behavior as a heritable trait in pigs and provide a basis to further investigate the genetic regulation of feeding rhythms in mammals and explore its use in animal breeding programs to improve feed efficiency and resilience. Significance Statement The timing of feed intake influences metabolism and health, but the genetic basis of feeding rhythms is poorly understood. Pigs are diurnal omnivores with daytime-dominated feeding patterns resembling those of humans, making them a useful model for studying circadian traits. Using over 40 million feeding records, we show that individual differences in 24-h feeding rhythmicity are highly heritable. Pigs with higher rhythmicity eat less at night and convert feed into growth more efficiently. A genomic region on porcine chromosome 4 near two candidate genes, OPRK1 and NPBWR1 , explains a substantial proportion of variation in feeding rhythmicity. These findings suggest that feeding rhythmicity may be a useful target trait for improving feed efficiency and resilience in livestock via selective breeding.

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