Porcine ear necrosis is associated with social behaviours in weaned piglets.

BACKGROUND: Porcine ear necrosis (PEN) is a worldwide health issue and its aetiology is still unclear. The aim of this study was to describe the prevalence and the severity of PEN in a commercial farm, associated with pig behaviour and health biomarkers measures. On two consecutive batches, PEN prevalence was determined at the pen level. PEN scores, blood haptoglobin concentration and oxidative status were measured on two pigs per pen (n = 48 pens) 9, 30 and 50 days (D) after arrival to the post-weaning unit. Social nosing, oral manipulation and aggression of pen mates and exploration of enrichment materials were observed on two to three pigs per pen twice a week from D9 to D50. RESULTS: At the pen level, the higher the time spent nosing pen mates, the lower the percentage of pigs affected by PEN during both the early and the late post-weaning periods (P < 0.002) and, in the opposite, the higher the time spent orally manipulating pen mates during the late post-weaning period, the higher the percentage of affected pigs (P = 0.03). At the pig level, the higher the increase in hydroperoxides and haptoglobin during the early post-weaning period, the higher the PEN scores on D30 (P < 0.001). CONCLUSIONS: This study suggests that a high incidence of social nosing, which can be an indicator of good social cohesion in a group, was significantly associated with less frequent lesions of PEN. In opposite, high incidence of oral manipulation of pen mates may increase the percentage of PEN-affected pigs. According to these observations, PEN is a multifactorial condition which may have social causes among others.

Dietary sialylated oligosaccharides in early-life may promote cognitive flexibility during development in context of obesogenic dietary intake.

Introduction: Oligosaccharides found in mammalian milk have shown the potential to alter brain development across multiple species. The diversity and concentration of these oligosaccharides is species-specific and varies greatly between individuals, thus understanding their role in cognitive development is warranted. We investigated the impact of early life dietary fucosylated/neutral or sialylated human milk oligosaccharides (HMO) on behaviours in tasks assessing anxiety, motivation, appetite, learning, and memory.Methods: Sixty-four female Göttingen minipigs were artificially reared from 2 weeks postnatal and provided milk replacers. The study used four groups: no additional oligosaccharides (Con), fucosylated and neutral oligosaccharides (FN, 4 g/L), sialylated oligosaccharides (SL, 0.68 g/L), or both FN and SL (FN + SL, 4 g/L) from 2 to 11 weeks postnatal. One reference group was sow-reared. Weaning occurred between 10 and 11 weeks postnatal, and thereafter an obesogenic diet was provided. Behavioral tasks were conducted over three periods: 1) 0-11 weeks; 2) 16-29 weeks; 3) 39-45 weeks. Tasks included a spatial holeboard task, open field task, exposure to a novel object, runway task, single-feed task, and home pen behaviour observation.Results: In the holeboard, the SL group demonstrated improved reference memory during reversal trials between 16-29 weeks. All groups demonstrated equivalent behavior in open field, novel object, runway, and single-feed tasks, as well as in their home pens (Ps > 0.05).Discussion: These results suggest that early life dietary intake of sialylated oligosaccharides may provide an improvement to cognition during the equivalent developmental stage of adolescence.

Lactose and Digestible Maltodextrin in Milk Replacers Differently Affect Energy Metabolism and Substrate Oxidation: A Calorimetric Study in Piglets.

BACKGROUND: In recent years, lactose-free infant formulas have been increasingly used. Digestible maltodextrins are commonly used as a substitute for lactose in these formulas, but the effects on energy metabolism are unknown. OBJECTIVE: We aimed to evaluate the differences in energy metabolism and substrate oxidation in piglets fed milk replacers containing lactose compared with maltodextrin as the only source of carbohydrates. METHODS: Piglets (Tempo × Topigs 20) from 8 litters were fed milk replacers containing lactose or maltodextrin (28% w/w, milk powder basis) from 1 to 9 wk of age (n =  4 litters/milk replacer). At 5 wk of age, 4 females and 4 entire males (mean ± SEM bodyweight, 10 ± 0.3 kg) were selected per litter, and housed in 16 groups of 4 littermates, with 2 females and 2 males per pen (n = 8 groups/milk replacer). Between 7 and 9 wk of age, groups were housed for 72 h in climate respiration chambers, and fed their experimental milk replacer in 2 meals per day, at 08:30 and 16:30. Heat production data were calculated from the continuous measurement of gaseous exchanges and analyzed using general linear models in SAS. RESULTS: Resting metabolic rate was 6% less in maltodextrin- than in lactose-fed piglets, notably before the morning meal. The postprandial respiratory quotient was 13% greater in maltodextrin- than in lactose-fed piglets after both meals. Net rates of carbohydrate oxidation were on average 5% greater in maltodextrin- than in lactose-fed piglets, particularly after the afternoon meal, whereas net rates of fat oxidation were 9% less in maltodextrin- than in lactose-fed piglets, particularly after the morning meal. CONCLUSIONS: Compared with lactose, maltodextrin in milk replacers reduced resting metabolic rate in the fasting state, and induced a shift in postprandial substrate oxidation profiles in pigs. Further research is warranted to evaluate the consequences of these metabolic changes for body composition.

Effects of maternal dietary nitrate supplementation during the perinatal period on piglet survival, body weight, and litter uniformity.

The objective of this study was to evaluate effects of different dosages of dietary nitrate supplementation to sows from d 108 of gestation until d 5 of lactation on reproductive performance of sows and piglet performance from birth until weaning. Dietary nitrate supplementation leads to nitric oxide (NO) formation that can potentially increase blood flow to the fetuses (by the vasodilative effect of NO), leading to a decrease in the loss of potential viable piglets in the form of stillbirth and preweaning mortality. Three hundred and five gilts and sows were allocated to one of six diets from d 108 of gestation until d 5 of lactation, containing 0.00% (Control), 0.03%, 0.06%, 0.09%, 0.12%, or 0.15% of dietary nitrate. The source of nitrate used was calcium nitrate double salt. Calcium levels were kept the same among diets by using limestone. Gilts and sows were weighed and backfat was measured at arrival to the farrowing room (d 108 of gestation) and at weaning (d 27 of age). Data included number of piglets born alive, born dead, and weaned, as well as individual piglet weights at d 0, 72 h of age and weaning. Preweaning mortality was determined throughout lactation. Body weight d 0 (P = 0.04) as well as BW at 72 h of age (P < 0.01) increased linearly with increasing dosages of nitrate in the maternal diet. Litter uniformity (SD) at birth was not affected by maternal nitrate supplementation level (P > 0.10), but tended to be higher at 72 h of age in the control treatment than in all nitrate-supplemented treatments (P = 0.07), and SD decreased linearly (increased uniformity) at weaning with increasing dosages of nitrate (P = 0.05). BW at weaning (P > 0.05) and average daily gain of piglets during lactation (P > 0.05) were not affected by maternal nitrate supplementation. A tendency for a quadratic effect (P = 0.10) of the dosage of maternal dietary nitrate was found on preweaning mortality of piglets with the lowest level of mortality found at 0.09% to 0.12% of maternal nitrate supplementation. We conclude that the use of nitrate in the maternal diet of sows during the perinatal period might stimulate preweaning piglet vitality. Exact mode of action and optimal dose of nitrate still need to be elucidated.

Maternal Western diet during gestation and lactation modifies adult offspring's cognitive and hedonic brain processes, behavior, and metabolism in Yucatan minipigs.

This study explores the long-term effects of exposure to a maternal Western diet (WD) vs. standard diet (SD) in the Yucatan minipig, on the adult progeny at lean status ( n = 32), and then overweight status. We investigated eating behavior, cognitive abilities, brain basal glucose metabolism, dopamine transporter availability, microbiota activity, blood lipids, and glucose tolerance. Although both groups demonstrated similar cognitive abilities in a holeboard test, WD pigs expressed a higher stress level than did SD pigs (immobility, P < 0.05) and lower performance in an alley maze ( P = 0.06). WD pigs demonstrated lower dopamine transporter binding potential in the hippocampus and parahippocampal cortex ( P < 0.05 for both), as well as a trend in putamen ( P = 0.07), associated with lower basal brain activity in the prefrontal cortex and nucleus accumbens ( P < 0.05) compared with lean SD pigs. Lean WD pigs demonstrated a lower glucose tolerance than did SD animals (higher glucose peak, P < 0.05) and a tendency to a higher incremental area under the curve of insulin from 0 to 30 minutes after intravenous glucose injection ( P < 0.1). Both groups developed glucose intolerance with overweight, but WD animals were less impacted than SD animals. These results demonstrate that maternal diet shaped the offspring's brain functions and cognitive responses long term, even after being fed a balanced diet from weaning, but behavioral effects were only revealed in WD pigs under anxiogenic situation; however, WD animals seemed to cope better with the obesogenic diet from a metabolic standpoint.-Gautier, Y., Luneau, I., Coquery, N., Meurice, P., Malbert, C.-H., Guerin, S., Kemp, B., Bolhuis, J. E., Clouard, C., Le Huërou-Luron, I., Blat, S., Val-Laillet, D. Maternal Western diet during gestation and lactation modifies adult offspring's cognitive and hedonic brain processes, behavior, and metabolism in Yucatan minipigs.

A milk formula containing maltodextrin, vs. lactose, as main carbohydrate source, improves cognitive performance of piglets in a spatial task.

In recent years, lactose-free and low-lactose infant formulas have been increasingly used. The impact of using different carbohydrates than lactose on later cognition of formula-fed infants remains, however, unknown. We examined the effects of providing formulas containing either digestible maltodextrin or lactose as main carbohydrate source (28% of total nutrient composition) on cognitive performance of piglets. Piglets received the formulas from 1 to 9 weeks of age and, starting at 12 weeks, were individually tested in a spatial holeboard task (n = 8 pens/formula), in which they had to learn and memorize a configuration of baited buckets. After 28 acquisition trials, piglets were subjected to 16 reversal trials in which the location of the baited buckets was changed. Piglets fed the maltodextrin-based formula had higher reference memory (RM) scores than piglets fed the lactose-based formula towards the end of acquisition. During the switch of configuration, piglets offered the maltodextrin-based formula tended to have higher RM scores and make fewer RM errors than piglets offered the lactose-based formula. Working (short-term) memory was not affected by the formulas. Compared to lactose, the use of maltodextrin in milk formulas improved long-term spatial memory of piglets, even weeks after the end of the intervention.

A maternal Western diet during gestation and lactation modifies offspring's microbiota activity, blood lipid levels, cognitive responses, and hippocampal neurogenesis in Yucatan pigs.

A suboptimal early nutritional environment (i.e., excess of energy, sugar, and fat intake) can increase susceptibility to diseases and neurocognitive disorders. The purpose of this study was to investigate in nonobese Yucatan minipigs (Sus scrofa) the impact of maternal diet [standard diet (SD) vs. Western diet (WD)] during gestation and 25 d of lactation on milk composition, blood metabolism, and microbiota activity of sows (n = 17) and their piglets (n = 65), and on spatial cognition (n = 51), hippocampal plasticity (n = 17), and food preferences/motivation (n = 51) in the progeny. Milk dry matter and lipid content, as well as plasma total cholesterol and free fatty acid (FFA) concentrations (P < 0.05) were higher in WD than in SD sows. Microbiota activity decreased in both WD sows and 100-d-old piglets (P < 0.05 or P < 0.10, depending on short-chain FAs [SCFAs]). At weaning [postnatal day (PND) 25], WD piglets had increased blood triglyceride and FFA levels (P < 0.01). Both SD and WD piglets consumed more of a known SD than an unknown high-fat and -sucrose (HFS) diet (P < 0.0001), but were quicker to obtain HFS rewards compared with SD rewards (P < 0.01). WD piglets had higher working memory (P = 0.015) and reference memory (P < 0.001) scores, which may reflect better cognitive abilities in the task context and a higher motivation for the food rewards. WD piglets had a smaller hippocampal granular cell layer (P = 0.03) and decreased neurogenesis (P < 0.005), but increased cell proliferation (P < 0.001). A maternal WD during gestation and lactation, even in the absence of obesity, has significant consequences for piglets' blood lipid levels, microbiota activity, gut-brain axis, and neurocognitive abilities after weaning.-Val-Laillet, D., Besson, M., Guérin, S., Coquery, N., Randuineau, G., Kanzari, A., Quesnel, H., Bonhomme, N., Bolhuis, J. E., Kemp, B., Blat, S., Le Huërou-Luron, I., Clouard, C. A maternal Western diet during gestation and lactation modifies offspring's microbiota activity, blood lipid levels, cognitive responses, and hippocampal neurogenesis in Yucatan pigs.

Familiarity to a Feed Additive Modulates Its Effects on Brain Responses in Reward and Memory Regions in the Pig Model.

Brain responses to feed flavors with or without a feed additive (FA) were investigated in piglets familiarized or not with this FA. Sixteen piglets were allocated to 2 dietary treatments from weaning until d 37: the naive group (NAI) received a standard control feed and the familiarized group (FAM) received the same feed added with a FA mainly made of orange extracts. Animals were subjected to a feed transition at d 16 post-weaning, and to 2-choice feeding tests at d 16 and d 23. Production traits of the piglets were assessed up to d 28 post-weaning. From d 26 onwards, animals underwent 2 brain imaging sessions (positron emission tomography of 18FDG) under anesthesia to investigate the brain activity triggered by the exposure to the flavors of the feed with (FA) or without (C) the FA. Images were analyzed with SPM8 and a region of interest (ROI)-based small volume correction (p < 0.05, k ≥ 25 voxels per cluster). The brain ROI were selected upon their role in sensory evaluation, cognition and reward, and included the prefrontal cortex, insular cortex, fusiform gyrus, limbic system and corpus striatum. The FAM animals showed a moderate preference for the novel post-transition FA feed compared to the C feed on d 16, i.e., day of the feed transition (67% of total feed intake). The presence or absence of the FA in the diet from weaning had no impact on body weight, average daily gain, and feed efficiency of the animals over the whole experimental period (p ≥ 0.10). Familiar feed flavors activated the prefrontal cortex. The amygdala, insular cortex, and prepyriform area were only activated in familiarized animals exposed to the FA feed flavor. The perception of FA feed flavor in the familiarized animals activated the dorsal striatum differently than the perception of the C feed flavor in naive animals. Our data demonstrated that the perception of FA in familiarized individuals induced different brain responses in regions involved in reward anticipation and/or perception processes than the familiar control feed flavor in naive animals. Chronic exposure to the FA might be necessary for positive hedonic effects, but familiarity only cannot explain them.

Perinatal Exposure to a Diet High in Saturated Fat, Refined Sugar and Cholesterol Affects Behaviour, Growth, and Feed Intake in Weaned Piglets.

The increased consumption of diets high in saturated fats and refined sugars is a major public health concern in Western human societies. Recent studies suggest that perinatal exposure to dietary fat and/or sugar may affect behavioural development. We thus investigated the effects of perinatal exposure to a high-fat high-sugar diet (HFS) on behavioural development and production performance of piglets. Thirty-two non-obese sows and their piglets were allocated to 1 of 4 treatments in a 2 × 2 factorial design, with 8-week prenatal (gestation) and 8-week postnatal (lactation and post-weaning) exposure to a HFS diet (12% saturated fat, 18.5% sucrose, 1% cholesterol) or control low-fat low-sugar high-starch diets as factors. From weaning onwards (4 weeks of age), piglets were housed in group of 3 littermates (n = 8 groups/treatment) and fed ad libitum. After the end of the dietary intervention (8 weeks of age), all the piglets were fed a standard commercial diet. Piglet behaviours in the home pens were scored, and skin lesions, growth, feed intake and feed efficiency were measured up to 8 weeks after the end of the dietary treatment, i.e. until 16 weeks of age. At the end of the dietary treatment (8 weeks of age), response to novelty was assessed in a combined open field and novel object test (OFT/NOT). During the weeks following weaning, piglets fed the postnatal HFS diet tended to be less aggressive (p = 0.06), but exhibited more oral manipulation of pen mates (p = 0.05) than controls. Compared to controls, piglets fed the prenatal or postnatal HFS diet walked more in the home pen (p ≤ 0.05), and tended to have fewer skin lesions (p < 0.10). Several behavioural effects of the postnatal HFS diet depended on the prenatal diet, with piglets subjected to a switch of diet at birth being more active, and exploring feeding materials, pen mates, and the environment more than piglets that remained on the same diet. Behaviours during the OFT/NOT were not affected by the diet. The intake of the postnatal HFS diet drastically reduced feed intake, but improved feed efficiency up to 8 weeks after the end of the dietary intervention, i.e. 16 weeks of age (p < 0.0001 for both). Our study highlights the key role of prenatal and postnatal nutritional interactions for early behavioural development, and reveals programming effects of early life nutrition on voluntary feed intake of piglets later in life.

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.

Maternal Fish Oil Supplementation Affects the Social Behavior, Brain Fatty Acid Profile, and Sickness Response of Piglets.

BACKGROUND: Maternal dietary docosahexaenoic acid (DHA) intake is thought to affect development in the offspring. OBJECTIVE: We assessed the impact of maternal dietary DHA on behavior, brain fatty acid (FA) profile, and sickness response of offspring in pigs, a pertinent model for human nutrition. METHODS: Sows (n = 24) were fed a diet with DHA-rich fish oil (FO) (20 g/kg) or high-oleic acid sunflower oil (HOSF) (20 g/kg) from day 61 of gestation through lactation. At 4 wk of age, 4 piglets per litter were weaned and mixed with piglets from other litters. Behavior was observed in 4- to 8-wk-old piglets, and brain FA composition was analyzed at 4 (n = 15) and 14 (n = 12) wk. Thirteen-week-old piglets (n = 48) were subjected to a lipopolysaccharide (LPS) challenge. Body temperature, plasma cytokines, and motivation to approach a familiar human, indicative of a sickness response, were measured. RESULTS: FO-fed pigs displayed more social activities (+262%, P = 0.02), played more (+61%, P = 0.03), and tended to show fewer oral manipulative behaviors directed at pen mates (-25%, P = 0.06) than did HOSF-fed pigs up to 4 wk after weaning. Brain DHA concentrations were higher in FO- than in HOSF-fed pigs up to 10 wk after supplementation (+10-50%, P < 0.001), although differences declined with age. Body temperature (P < 0.001) and tumor necrosis factor α and interferon Î³ concentrations (P < 0.05) increased after LPS injection, but no diet effect was found (P > 0.10). LPS-treated pigs were less likely to approach the human than saline-treated pigs in the HOSF-fed (-29%, P = 0.0003), but not in the FO-fed group (-13%, P = 0.11). CONCLUSIONS: Maternal DHA beneficially affected offspring social behavior after weaning and mildly attenuated sickness behavior after an inflammatory challenge in pigs. These behavioral changes may be mediated by increased brain DHA proportions.

Dietary linoleic and α-linolenic acids affect anxiety-related responses and exploratory activity in growing pigs.

BACKGROUND: Growing evidence suggests that the dietary ratio of linoleic acid (LA) to α-linolenic acid (ALA), the precursors of arachidonic acid (AA) and docosahexaenoic acid (DHA), respectively, may affect behavior in mammals. OBJECTIVE: This study aimed at evaluating the impact of dietary LA and ALA intake on behaviors of growing pigs, a pertinent model for human nutrition. METHODS: At 7 wk of age, 32 pigs were allocated to 4 dietary treatments varying in daily intake of LA (1.3 and 2.6 g · kg body weight(-0.75) · d(-1) for low- and high-LA groups, respectively) and ALA (0.15 and 1.5 g · kg body weight(-0.75) · d(-1) for low- and high-ALA groups, respectively) for 4 wk. Between days 12 and 18, general behavior in the home pen was observed and pigs were subjected to an open field and novel object test. At 11 wk of age, brain fatty acid composition was analyzed. RESULTS: Compared with high LA intake, low LA intake increased the time spent on exploration, particularly nosing in the home pen (P < 0.05) and the open field (P < 0.05), and tended to reduce the time spent lying with eyes open in the home pen (P = 0.09). Time spent lying with eyes open also tended to be affected by the interaction between LA and ALA (P = 0.08). A high-LA/high-ALA intake (ratio of 2; P < 0.05) and a low-LA/high-ALA intake (ratio of 1; P = 0.06) decreased the latency to approach the novel object compared with a low-LA/low-ALA intake (ratio of 9). DHA in the frontal cortex was positively correlated with exploratory behaviors in the home pen (rs = 0.56, P < 0.01), whereas AA was negatively correlated with time spent lying with eyes closed (rs = -0.48, P < 0.01). CONCLUSIONS: Low LA intake and a low dietary LA:ALA ratio increased exploration and decreased anxiety-related behaviors in pigs. It is suggested that changes in brain DHA and AA induced by dietary LA and ALA intake mediate these behavioral changes.

Combined compared to dissociated oral and intestinal sucrose stimuli induce different brain hedonic processes.

The characterization of brain networks contributing to the processing of oral and/or intestinal sugar signals in a relevant animal model might help to understand the neural mechanisms related to the control of food intake in humans and suggest potential causes for impaired eating behaviors. This study aimed at comparing the brain responses triggered by oral and/or intestinal sucrose sensing in pigs. Seven animals underwent brain single photon emission computed tomography ((99m)Tc-HMPAO) further to oral stimulation with neutral or sucrose artificial saliva paired with saline or sucrose infusion in the duodenum, the proximal part of the intestine. Oral and/or duodenal sucrose sensing induced differential cerebral blood flow changes in brain regions known to be involved in memory, reward processes and hedonic (i.e., pleasure) evaluation of sensory stimuli, including the dorsal striatum, prefrontal cortex, cingulate cortex, insular cortex, hippocampus, and parahippocampal cortex. Sucrose duodenal infusion only and combined sucrose stimulation induced similar activity patterns in the putamen, ventral anterior cingulate cortex and hippocampus. Some brain deactivations in the prefrontal and insular cortices were only detected in the presence of oral sucrose stimulation. Finally, activation of the right insular cortex was only induced by combined oral and duodenal sucrose stimulation, while specific activity patterns were detected in the hippocampus and parahippocampal cortex with oral sucrose dissociated from caloric load. This study sheds new light on the brain hedonic responses to sugar and has potential implications to unravel the neuropsychological mechanisms underlying food pleasure and motivation.

An attempt to condition flavour preference induced by oral and/or postoral administration of 16% sucrose in pigs.

The present study investigated the acquisition of conditioned flavour preferences in pigs using the caloric value and/or sweet taste of sucrose. Nine water-deprived juvenile pigs were given four three-day conditioning sessions during which they received flavoured solutions as conditioned stimuli (CS). The CS solutions were paired with three treatments that generated a gustatory and/or a caloric reinforcement (US). The CS++ solution was added with 16% sucrose and paired with an intraduodenal (ID) infusion of water, the CS+ solution was paired with an ID infusion of 16% sucrose and the CS- solution was paired with an ID infusion of water. One and two weeks after conditioning, the water-deprived pigs were subjected to two-choice preference tests with the unreinforced CS solutions. Solutions intake, behavioural activity and some drinking parameters were measured. Despite no difference in CS intake during conditioning, the animals spent less time inactive and more time standing during CS++ than CS+ conditioning. When receiving CS++, the pigs explored the drinking trough more than when receiving CS-. Compared to the CS- condition, the numbers of drinking episodes and intra-drinking episode (IDE) pauses were also 36% and 49% lesser in the CS++ condition, but these differences were not significant. During the two-choice tests, the pigs did not show significant preferences. Nevertheless, during the first session, the pigs seemed to show a slight preference for the CS++ (57% of total intake) compared to CS+. The duration of CS++ drinking episodes represented 64% of the total duration compared to CS+ and CS- . The total time spent drinking the CS++ also represented 57% of the total time in the CS++ vs. CS- test. To conclude, although no clear-cut preferences were found during two-choice tests, the oral perception of 16% sucrose during conditioning induced changes in behavioural activities, motivational responses and microstructure of CS intake, suggesting the importance of oral food perception for food selection processes in pigs. Further studies are needed to investigate the impact of water deprivation on the expression of flavour preferences in pigs.

Exposures to conditioned flavours with different hedonic values induce contrasted behavioural and brain responses in pigs.

This study investigated the behavioural and brain responses towards conditioned flavours with different hedonic values in juvenile pigs. Twelve 30-kg pigs were given four three-day conditioning sessions: they received three different flavoured meals paired with intraduodenal (i.d.) infusions of 15% glucose (F(Glu)), lithium chloride (F(LiCl)), or saline (control treatment, F(NaCl)). One and five weeks later, the animals were subjected to three two-choice feeding tests without reinforcement to check the acquisition of a conditioned flavour preference or aversion. In between, the anaesthetised pigs were subjected to three (18)FDG PET brain imaging coupled with an olfactogustatory stimulation with the conditioned flavours. During conditioning, the pigs spent more time lying inactive, and investigated their environment less after the F(LiCl) than the F(NaCl) or F(Glu) meals. During the two-choice tests performed one and five weeks later, the F(NaCl) and F(Glu) foods were significantly preferred over the F(LICl) food even in the absence of i.d. infusions. Surprisingly, the F(NaCl) food was also preferred over the F(Glu) food during the first test only, suggesting that, while LiCl i.d. infusions led to a strong flavour aversion, glucose infusions failed to induce flavour preference. As for brain imaging results, exposure to aversive or less preferred flavours triggered global deactivation of the prefrontal cortex, specific activation of the posterior cingulate cortex, as well as asymmetric brain responses in the basal nuclei and the temporal gyrus. In conclusion, postingestive visceral stimuli can modulate the flavour/food hedonism and further feeding choices. Exposure to flavours with different hedonic values induced metabolism differences in neural circuits known to be involved in humans in the characterization of food palatability, feeding motivation, reward expectation, and more generally in the regulation of food intake.

Asymmetry of behavioral responses to a human approach in young naive vs. trained horses.

The aim of this study was to investigate the impact of training experience on young horses (Equus caballus)' lateralized responses to an approaching human. The results show that the one year old untrained horses display asymmetrical responses to an approaching human, with more negative reactions (escapes, threats) when approached from the left side, while approaches towards the right shoulder elicited more positive behaviors. On the contrary, two years old trained horses reacted equally positively to approaches and contact on both sides. Our findings support those of previous studies investigating a link between emotionality and laterality and confirm the role of the left hemisphere in the processing of novel or negative stimuli. Moreover, the data underline the impact work and training can have on this laterality in horses.