The effects of sensory functional ingredients on food preferences, intake and weight gain in juvenile pigs

Alfalfa leaf meal as a new protein feedstuff improves meat quality by modulating lipid metabolism and antioxidant capacity of finishing pigs

The effects of alfalfa leaf meal (ALM) on the meat quality of finishing pigs are largely unknown. Here, we investigated the effects of ALM diet on meat quality by replacing 0%, 25%, 50%, and 75% of soybean meal in the diet of finishing pigs, respectively. The findings showed that 25% ALM diet increased the IMF, cooked meat rate, a* and antioxidant capacity of longissimus dorsi (LD), improved amino acid composition, increased MUFA content, and increased LD lipid synthesis and mRNA expression of antioxidation-related genes. At the same time, ALM diet altered serum lipid metabolism (TG, FFA). Correlation analysis showed that antioxidant capacity was positively correlated with meat quality. In addition, metabolomic analysis of LD showed that the main metabolites of 25% ALM diet altered stachydrine and l-carnitine were associated with meat quality and antioxidant capacity. In conclusion, ALM replacing 25% soybean meal diet can improve the meat quality of pigs.

Exposure to a sensory functional ingredient in the pig model modulates the blood-oxygen-level dependent brain responses to food odor and acute stress during pharmacological MRI in the frontostriatal and limbic circuits

Introduction

In the present study, we examined the effects of a supplementation with a sensory functional ingredient (FI, D16729, Phodé, France) containing vanillin, furaneol, diacetyl and a mixture of aromatic fatty acids on the behavioural and brain responses of juvenile pigs to acute stress.

Methods

Twenty-four pigs were fed from weaning with a standard granulated feed supplemented with the functional ingredient D16729 (FS animals, N = 12) or a control formulation (CT animals, N = 12). After a feed transition (10 days after weaning), the effects of FI were investigated on eating behaviour during two-choice feed preference tests. Emotional reactivity to acute stress was then investigated during openfield (OF), novel suddenly moving object (NSO), and contention tests. Brain responses to the FI and the two different feeds' odour, as well as to an acute pharmacological stressor (injection of Synacthen®) were finally investigated with functional magnetic resonance imaging (fMRI).

Results

FS animals tended to spend more time above the functional feed (p = 0.06) and spent significantly more time at the periphery of the arena during NSO (p < 0.05). Their latency to contact the novel object was longer and they spent less time exploring the object compared to CT animals (p < 0.05 for both). Frontostriatal and limbic responses to the FI were influenced by previous exposure to FI, with higher activation in FS animals exposed to the FI feed odor compared to CT animals exposed to a similarly familiar feed odor without FI. The pharmacological acute stress provoked significant brain activations in the prefrontal and thalamic areas, which were alleviated in FS animals that also showed more activity in the nucleus accumbens. Finally, the acute exposure to FI in naive animals modulated their brain responses to acute pharmacological stress.

Discussion

Overall, these results showed how previous habituation to the FI can modulate the brain areas involved in food pleasure and motivation while alleviating the brain responses to acute stress.

Impact of a Dietary Citrus Extract on the Behavior and Production of Lactating Dairy Cows Following Regrouping: A Preliminary Study

Exposure of lab animals, humans, and pigs to olfactory sensory feed additives may reduce response to stress and anxiety. The objective of this preliminary study was to determine if feeding a citrus-based olfactory sensory functional feed extract (derived from Citrus sinensis) reduces the negative impact of regrouping of lactating dairy cows. Thirty-two (parity = 2.0 ± 1.2; mean ± SD), mid-lactation Holstein dairy cows (169.8 ± 16.8 DIM) were enrolled as focal cows in this study and housed individually in a tie-stall facility where they were randomly assigned to 1 of 2 treatment diets: (1) control total mixed ration (TMR) (control; n = 16; primiparous = 7; multiparous = 9), or (2) control TMR with 4 g/d of citrus extract (CE) (Phodé, Terssac, France) (CE; n = 16; primiparous = 7; multiparous = 9). Cows were fed their experimental diets for 7 d in the tie-stall facility (baseline), then moved to 1 of 2 experimental free-stall pens (containing 29 other cows) for a period of 7 d, where they remained on the same treatment diet as before. Compared with their baseline, primiparous control cows had decreased rumination time on d 1 and 2, had decreased lying time on d 1, and tended to have decreased lying time on d 2 and 3 following regrouping. In contrast, primiparous cows fed the CE diet did not experience a change in rumination and lying time. Primiparous CE cows had greater feeding time on d 1 and tended to have greater feeding time on d 2 after regrouping compared to primiparous control cows. Primiparous control cows had greater idle standing time, as compared to the CE cows, across the 7 d after regrouping. Primiparous CE cows initiated less total competitive behavior after regrouping, but were also displaced more frequently from the feed bunk and from the free stalls on d 1 after regrouping, as compared to the primiparous control cows. For multiparous cows, CE supplementation was not consistently associated with any benefits to behavior or production after regrouping, possibly because these cows were more experienced with social stressors. Results indicate that feeding CE to mid-lactation naïve primiparous dairy cows may reduce the initiation of competitive interactions and lessen the reduction in rumination and lying time after regrouping. These results need to be verified in further studies where potential confounding effects (e.g., pen social dynamics, pen location) are minimized.

Prenatal Exposure to Innately Preferred D-Limonene and Trans-Anethole Does Not Overcome Innate Aversion to Eucalyptol, Affecting Growth Performance of Weanling Piglets

Simple Summary

Weanling piglets appear to be poorly adapted and motivated to ingest solid feed due to the innate reluctance of young animals to ingest an unfamiliar feed or flavor, i.e., feed neophobia, which commonly results in a period of underfeeding. This, and other common wean stress factors, lead to gastrointestinal disorders and impaired growth performance. Increasing the preference or familiarity for a certain type of food or for specific flavors may improve voluntary feed intake in weanling piglets. Botanical compounds (BCs) are described as functional feed additives and include sensorial properties that are able to influence feed intake and growth in pigs by dietary supplementation or sensory maternal learning. In this study, the effects of BCs such as D-limonene, trans-anethole, and eucalyptol on innate feed preference and growth performance of weanling piglets were evaluated by means of a double-choice feeding test and pre- and postnatal exposure to these compounds.

Abstract

In the present research, two studies were performed to determine the effects of specific botanical compounds (BCs) on the innate feed preference and feed intake of piglets, as follows: Exp. 1 studied the innate feed preferences of post-weaning piglets using a double-choice feeding test. A total of 828 weaned piglets were distributed into 36 pens (23 pigs/pen) and assigned to three dietary pair choice feeding options (n = 12): unsupplemented prestarter diets (reference) versus reference plus D-limonene, trans-anethole, or eucalyptol. Piglets showed a preference for diets with D-limonene (53.8%) and trans-anethole (54.5%), and an aversion to eucalyptol (41.6%) (p < 0.05). Exp. 2 studied whether the prenatal and perinatal exposure to D-limonene, trans-anethole, and eucalyptol influences the feed intake and growth of newly-weaned piglets. Twenty-eight gestating and lactating sows were distributed into two dietary treatments (n = 14): unsupplemented Control diets or Control plus a blend of BCs (BBC; containing D-limonene, trans-anethole, and eucalyptol). D-limonene, trans-anethole, and eucalyptol were transferred into the placental fluid, and D-limonene and trans-anethole into the milk (p < 0.05). Furthermore, weanling piglets (n = 200; Control) and (n = 203; BBC) received the same treatment as their mothers in prestarter diets. The early response after weaning showed that piglets’ post-weaning BW gain was higher in the Control (p < 0.05) group than in those exposed to BBC. In conclusion, prenatal exposure to preferred D-limonene and trans-anethole, or familiarity to eucalyptol did not help to overcome the innate aversion to eucalyptol and its negative effect on weanling piglets’ BW.

Insights into suckling rabbit feeding behaviour: acceptability of different creep feed presentations and attractiveness for sensory feed additives

In young rabbit, digestive disorders are frequently observed around weaning. Stimulating the onset of feed intake in the suckling rabbit might be a way to promote gut health. The aim of this study was to determine the rabbit's acceptability for different feed presentations and its preferences for flavours at an early stage of life. Two trials were conducted to evaluate the effects of physical form and flavouring on creep feed attractiveness. All the diets tested were provided in the nest from 3 to 17 days, and the daily intake per litter was recorded as of 8 days of age. In the first trial, five feed presentations were tested separately (n = 60 litters). Three dry presentations were chosen: commercial pellet (P), crumb from commercial pellet (cP) and crumb from beet pulp pellet (cBP). Hydrated feeds were also provided with either raw fodder beetroot (B) or a semi-solid feed in agar gel form produced with fodder beetroot juice and pulp (gB). In the second trial, double-choice tests were performed on four feed gels (n = 72 litters), leading to six comparison treatments. These agar gels were made of pellet mash without or with a sensory additive: one non-odorised control gel and three gels with 0.20% banana flavour, 0.06% red berry flavour and 0.10% vanilla flavour, respectively. In the first trial, kits ate more gB in fresh matter than other feed presentations (P < 0.001), with a total intake of 7.0 ± 1.8 g/rabbit from 8 to 17 days. In DM, the total consumption of pellets P (1.6 ± 0.4 g of DM/rabbit) was the highest together with the gB form (1.4 ± 0.4 g of DM/rabbit), whereas cBP was barely consumed (0.3 ± 0.1 g of DM/rabbit). Gel feed supplemented with vanilla was slightly more consumed than other flavoured and non-odorised gels (relative consumption of 57% when compared to control gel; P = 0.001). The gel feed intake was independent of the milk intake but was correlated with the litter weight at 3 days (r = 0.40, P < 0.001). In both trials, rabbit growth before and after weaning was not affected by the type of creep feed provided. Our results confirmed that providing creep feed promotes the solid intake of rabbits at early stages. Gel feed form motivated rabbits to eat and vanilla flavour supplementation increased the feed palatability. Those creep feed characteristics should be explored further for seeking effective stimulation of the onset of the feed intake in suckling rabbit.

Review: Impact of food, gut-brain signals and metabolic status on brain activity in the pig model: 10 years of nutrition research using in vivo brain imaging

The purpose of this review is to offer a panorama on 10 years of nutrition research using in vivo brain imaging in the pig model. First, we will review some work describing the brain responses to food signals, including basic tastants such as sweet and bitter at both oral and visceral levels, as well as conditioned preferred and aversive flavours. Second, we will have a look at the impact of weight gain and obesity on brain metabolism and functional responses, drawing the parallel with obese human patients. Third, we will evoke the concept of the developmental origins of health and diseases, and how the pig model can shed light on the importance of maternal nutrition during gestation and lactation for the development of the gut-brain axis and adaptation abilities of the progeny to nutritional environments. Finally, three examples of preventive or therapeutic strategies will be introduced: the use of sensory food ingredients or pre-, pro-, and postbiotics to improve metabolic and cognitive functions; the implementation of chronic vagus nerve stimulation to prevent weight gain and glucose metabolism alterations; and the development of bariatric surgery in the pig model for the understanding of its complex mechanisms at the gut-brain level. A critical conclusion will brush the limitations of neurocognitive studies in the pig model and put in perspective the rationale and ethical concerns underlying the use of pig experimentation in nutrition and neurosciences.

Long-term exposure to sensory feed additives during the gestational and postnatal periods affects sows' colostrum and milk sensory profiles, piglets' growth, and feed intake

This study investigated the effect of feed supplementation in sows and/or their progeny with 2 sensory feed additives (FA1: limonene and cinnamaldehyde; FA2: menthol, carvone, and anethole) on sows' feed intake, body weight, fat deposition, and colostrum/milk composition, as well as piglets' feed intake growth and feed efficiency from birth to slaughter at postnatal day 160 (PND160). During the last third of gestation and the whole of lactation, sows were subjected to a control diet (C) or the same diet containing FA1 or FA2 at 0.1% of complete feed content. Colostrum/milk samples were taken at days 1, 14, and 28 of lactation for gas chromatography-mass spectrometry analyses. After weaning, the progeny was subjected to a control diet (C) or experimental diets with a sweetener (0.015%) but no other additive (S), or to diets with a sweetener and the additive FA1 (FA1S) or FA2 (FA2S). There was no effect of dietary treatment on sows' feed intake, body weight, or adiposity (P > 0.15 for all), but the sensory characteristics of their colostrum/milk were modified by the diet and diet*time interaction. Limonene concentrations were higher in FA1 samples from PND1 to PND28, whereas carvone and anethole concentrations were higher in FA2 samples from PND1 to PND28. The concentration of these 3 compounds increased with time in the respective groups where they were mostly detected. Menthol concentrations were higher in FA2 samples at PND14 and PND28, but there was no time effect. Overall, cinnamaldehyde was always below the detection range. Piglets born from FA1 and FA2 sows had higher body weight (P = 0.034 at PND160), average daily gain (ADG; P = 0.036 for PND0-160), and average daily feed intake (ADFI; P = 0.006 for PND28-160) than piglets born from C sows. Overall, piglets that were never exposed to FA or only after weaning had lower ADG (P = 0.030 for PND0-160) and ADFI (P = 0.016 for PND28-160) than piglets that were exposed to FA only via the maternal diet, the condition combining both pre- and post-natal exposure being intermediary. In conclusion, FA1 and FA2 provided to gestating and lactating sows increased the progeny's feed intake and growth, suggesting nutritional programming and/or sensory conditioning during the perinatal period. Addition of FA only in the progeny's diet was not beneficial.

fMRI-Based Brain Responses to Quinine and Sucrose Gustatory Stimulation for Nutrition Research in the Minipig Model: A Proof-of-Concept Study

The minipig model is of high interest for brain research in nutrition and associated pathologies considering the similarities to human nutritional physiology, brain structures, and functions. In the context of a gustatory stimulation paradigm, fMRI can provide crucial information about the sensory, cognitive, and hedonic integration of exteroceptive stimuli in healthy and pathological nutritional conditions. Our aims were (i) to validate the experimental setup, i.e., fMRI acquisition and SPM-based statistical analysis, with a visual stimulation; (ii) to implement the fMRI procedure in order to map the brain responses to different gustatory stimulations, i.e., sucrose (5%) and quinine (10 mM), and (ii) to investigate the differential effects of potentially aversive (quinine) and appetitive/pleasant (sucrose) oral stimulation on brain responses, especially in the limbic and reward circuits. Six Yucatan minipigs were imaged on an Avanto 1.5-T MRI under isoflurane anesthesia and mechanical ventilation. BOLD signal was recorded during visual or gustatory (artificial saliva, sucrose, or quinine) stimulation with a block paradigm. With the visual stimulation, brain responses were detected in the visual cortex, thus validating our experimental and statistical setup. Quinine and sucrose stimulation promoted different cerebral activation patterns that were concordant, to some extent, to results from human studies. The insular cortex (i.e., gustatory cortex) was activated with both sucrose and quinine, but other regions were specifically activated by one or the other stimulation. Gustatory stimulation combined with fMRI analysis in large animals such as minipigs is a promising approach to investigate the integration of gustatory stimulation in healthy or pathological conditions such as obesity, eating disorders, or dysgeusia. To date, this is the first intent to describe gustatory stimulation in minipigs using fMRI.

Animal Models for the Study of the Relationships between Diet and Obesity: A Focus on Dietary Protein and Estrogen Deficiency

Obesity is an increasing major public health concern asking for dietary strategies to limit weight gain and associated comorbidities. In this review, we present animal models, particularly rats and mice, which have been extensively used by scientists to understand the consequences of diet quality on weight gain and health. Notably, modulation of dietary protein quantity and/or quality has been shown to exert huge effects on body composition homeostasis through the modulation of food intake, energy expenditure, and metabolic pathways. Interestingly, the perinatal window appears to represent a critical period during which the protein intake of the dam can impact the offspring’s weight gain and feeding behavior. Animal models are also widely used to understand the processes and mechanisms that contribute to obesity at different physiological and pathophysiological stages. An interesting example of such aspect is the situation of decreased estrogen level occurring at menopause, which is linked to weight gain and decreased energy expenditure. To study metabolic disorders associated with such situation, estrogen withdrawal in ovariectomized animal models to mimic menopause are frequently used. According to many studies, clear species-specific differences exist between rats and mice that need to be taken into account when results are extrapolated to humans.

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.

Impact of sensory feed additives on feed intake, feed preferences, and growth of female piglets during the early postweaning period

Our study aimed at investigating the effect of feed supplementation, from weaning, with 3 sensory feed additives (FA1, FA2, and FA3) on feed preferences, feed intake, and growth of piglets. The FA1 contained extract of Stevia rebaudiana (10 to 20%), extract of high-saponin plants (5 to 10%), and excipients (70 to 85%), the FA2 was mainly composed of a natural extract of Citrus sinensis (60 to 80%), and the FA3 was made of a blend of extracts of hot-flavored spices (5 to 15%) and excipients (85 to 95%). At weaning (d 1), a total of 32 female piglets housed in individual pens were allocated to 4 treatments (FA1, FA2, FA3, and control [CON]) of equivalent mean weight. The pigs were fed a standard pelleted prestarter diet from weaning (d 1) to d 15 and a starter diet from d 16 to 28. The diets were supplemented with the feed additives (FA) corresponding to their treatment, while the CON treatment was the standard diets with no additive. Feed refusals were weighed daily and piglets were weighed weekly on d 1, 7, 14, 21, and 28. On the day of feed transition (d 16) as well as 7 (d 23) and 10 d (d 26) later, the animals were consecutively subjected to 1- and 22-h double-choice feeding tests to investigate their preferences during a short period and a longer period of time for the CON starter diet and the starter diet added with the FA corresponding to their treatment. No overall effect of the feed additives was observed on ADFI, ADG, G:F, and final BW. No overall preference was highlighted for the FA1 treatment, except for a preference for the FA1 starter diet during the 1-h test on d 23 (78% of total feed intake; P < 0.01). For the FA2 treatment, the pigs consumed the FA2 starter diet more than the CON starter diet during the 22-h tests on d 16 (67% of total feed intake; P < 0.05) and 26 (62% of total feed intake; P < 0.01). For the FA3 treatment, on d 26, the FA3 starter diet was and tended to be consumed more than the CON starter diet during 1- (69% of total intake; P < 0.05) and 22-h (60% of total intake; P < 0.10) tests, respectively. In conclusion, feed supplementation with the FA1, FA2, and FA3 from weaning did not induce beneficial effects on feed intake and growth performance during the early postweaning period. The FA2 increased palatability and acceptance of the unfamiliar starter diet the day of feed transition, while the FA1 and FA3 increased palatability of the starter diet only after a few days of exposure, most likely through long-term familiarization processes.