Indirect Genetic Effects for Growth in Pigs Affect Behaviour and Weight Around Weaning.

Selection for indirect genetic effects (IGE), i.e. the genetic effect of an individual on a trait of another individual, is a promising avenue to increase trait values in plant and animal breeding. Studies in livestock suggest that selection for IGE for growth (IGEg) might increase animals' capacity to tolerate stress. We assessed the effect of a stressful phase (weaning) on the behaviour and performance of pigs (n = 480) divergently selected for high or low IGEg. High IGEg pigs were significantly slower to explore the feed and gained less weight than low IGEg pigs in the days after weaning. In line with previous findings, high IGEg animals may have prioritized the formation of social ranks.

Prenatal, but not early postnatal, exposure to a Western diet improves spatial memory of pigs later in life and is paired with changes in maternal prepartum blood lipid levels.

Maternal obesity and perinatal high-fat diets are known to affect cognitive development. We examined the effects of late prenatal and/or early postnatal exposure to a Western-type diet, high in both fat and refined sugar, on the cognition of pigs (Sus scrofa) in the absence of obesity. Thirty-six sows and their offspring were assigned to 1 of 4 treatments in a 2 × 2 factorial arrangement, with 8 wk prenatal and 8 wk postnatal exposure to a Western diet (enriched in fat, sucrose, and cholesterol) or control diets as factors. Compared to controls, piglets exposed to the prenatal Western diet showed enhanced working and reference memory during the acquisition and reversal phases of a spatial hole-board task. Mothers fed the prenatal Western diet had higher prepartum blood cholesterol and free fatty acid levels. Postnatal exposure to the Western diet did not affect piglet cognitive performance, but it did increase postpartum maternal and postweaning piglet cholesterol levels. The Western diet had no effect on maternal or offspring insulin sensitivity or leptin levels. In conclusion, a prenatal Western diet improved memory function in pigs, which was paired with changes in prepartum maternal blood cholesterol levels. These findings highlight the key role of late fetal nutrition for long-term programming of cognition.-Clouard, C., Kemp, B., Val-Laillet, D., Gerrits, W. J. J., Bartels, A. C., Bolhuis, J. E. Prenatal, but not early postnatal, exposure to a Western diet improves spatial memory of pigs later in life and is paired with changes in maternal prepartum blood lipid levels.

Working and reference memory of pigs (Sus scrofa domesticus) in a holeboard spatial discrimination task: the influence of environmental enrichment.

Interest in cognitive research in pigs is increasing, but little is known about the impact of environmental conditions on pigs' cognitive capabilities. The present study investigated the effect of environmental enrichment on cognitive performance of pigs in a holeboard spatial task, in which they had to discriminate four baited buckets out of 16. Pigs (n = 32) were either housed in stimulus-poor, barren pens, or in larger pens enriched with rooting substrates. Pigs were subjected to 30 holeboard trials. Both working memory (WM), that is, the ratio (baited visits/total number of (re)visits to baited buckets), and reference memory (RM), that is, the ratio ((re)visits to baited buckets/total number of visits to all buckets), improved over trials. WM scores were higher in pigs from enriched pens than in pigs from barren pens. Housing did not affect RM scores. Personality type of the pigs, as assessed early in life using a backtest, did not affect WM or RM. In conclusion, housing conditions of pigs did not affect reference memory, but environmental enrichment improved working memory of pigs in a spatial discrimination task. Based on the findings of this study, we suggest that cognitive functioning of pigs may be impaired under commonly used housing conditions.