Ewes bear scent glands located near the udder which smelly secretion is interesting to newly-born lambs searching a teat to suck on. This glands' secretion - inguinal wax (IW) - was found to be reactogenic to lambs before they initiate suckling from the dam. The present study aimed to further assess whether IW odor affects two vital aspects of newborn lambs' behaviour: orienting and engaging suckling. First, forty-six lambs were tested in two-choice odor tests contrasting i) own mother's Inguinal Wax (IW-M) vs. unfamiliar mother's Inguinal Wax (IW-nM), ii) IW-M vs. control and iii) IW-nM vs. control, to measure their differential orientation to maternal IW odor presented against either IW from another dam or a control. Second, a bottle-feeding test (n = 41 lambs) assessed lambs' elicitation of suckling from IW-odorized vs. control bottles. Relative to the control, IW odor enhanced lambs' orientation during the two-choice odor test, but without differentiation of maternal IW from non-maternal IW. Otherwise, lambs did not engage more suckling on a bottle when odorized with maternal IW relative to a control bottle. Some aspects of lambs' responses were differentiated by sex, but this effect was independent on odor condition. In sum, this preliminary study indicates that ovine IW is somehow inherently attractive to lambs before they associate it with suckling.

Amongst the array of sensory cues maternal ewes provide to their lambs, the role of odors still remains unclear in Ovis aries. Specifically, the communicatory potential on lambs of the scent released by the ewes’ perimammary inguinal glands is little studied. It is thus worthy to increase our insight about the adaptive value of ovine inguinal glands, the chemical nature of their secretion (i.e., inguinal wax, IW) and their communicative function in the success of initial suckling episodes. A first study explores whether IW from late pregnancy ewes differs from that of postparturient ewes in macroconstituents (lipids, proteins, water) as a proxy to changes in inguinal glands’ activity at the time when lambs’ teat searching and sucking are initiated. Then, the composition in volatile constituents is compared between IWs sampled at both physiological stages using solid-phase micro-extraction of the headspace and gas chromatography-mass spectrometry, allowing to identify 22 odor-active compounds. A second study assessed whether newly-born lambs discriminate the odor of IW from late-pregnancy ewes from that of IW from postparturient ewes (not their own mothers). While late-gestation IW tended to differ from postpartum IW in macroconstituents and in some volatile constituents, lambs seemed to respond indiscriminately in a behavioral test of choice between paired odors although they detected them. Thus, IW of any peripartum ewe (excluding the mother) is potent to elicit olfactory attraction in lambs ahead of the first suckling experience. Ovine IW is therefore in a good position to convey odor cues or a specific chemomessage that guides lambs toward the inguinal-mammary region of their mother.

Assessing olfaction in lambs presents methodological challenges due to their precocial development and extreme sensitivity to isolation and novelty. Previous research studied lambs' olfactory reactivity, particularly to odors from conspecifics, their responses to other odor sources remaining underexplored. To begin addressing this gap, we implemented two tests to evaluate olfactory discrimination in lambs using two distinct odors: dog feces odor (DO) and ovine wool odor (OO). First, after validating the procedure on 10 Suffolk ewes with the same odorous stimuli, a habituation-dishabituation (H-D) test run on 6-day-old lambs (Suffolk, n = 26, 14 females) consisted in repeating 4 times one odor for habituation, followed by a single presentation the other, novel odor for dishabituation (presentation order of OO/DO being counterbalanced across animals). The ewes and lambs habituated to both odors, exhibiting a significant decline in sniffing duration; they also dishabituated to novel odors, attesting their clear discrimination between them. Second, an approach-withdrawal test using boxes scented with these same stimuli was run a group of lambs p (Suffolk, age: 24-day, n = 21). In the approach test, lambs spent significantly more time near objects scented with unfamiliar conspecific wool than those scented with canine feces. Both tests confirmed that lambs clearly discriminate both odors. While the habituation-dishabituation test proved effective in assessing odor discrimination, interpretation of the approach test results was more complex under the given experimental conditions.

Human milk odor is attractive and appetitive for human newborns. Here, we studied behavioral and heart-rate (HR) responses of 2-day-old neonates to the odor of human colostrum. To evaluate detection in two conditions of stimulus delivery, we first presented the odor of total colostrum against water. Second, the hedonic specificity of total colostrum odor was tested against vanilla odor. Third, we delivered only the fresh effluvium of colostrum separated from the colostrum matrix; the stability of this colostrum effluvium was then tested after deep congelation; finally, after sorptive extraction of fresh colostrum headspace, we assessed the activity of colostrum volatiles eluting from the gas chromatograph (GC). Regardless of the stimulus-delivery method, neonates displayed attraction reactions (HR decrease) as well as appetitive oral responses to the odor of total colostrum but not to vanilla odor. The effluvium separated from the fresh colostrum matrix remained appetitive but appeared labile under deep freezing. Finally, volatiles from fresh colostrum effluvium remained behaviorally active after GC elution, although at lower magnitude. In sum, fresh colostrum effluvium and its eluate elicited a consistent increase in newborns' oral activity (relative to water or vanilla), and they induced shallow HR decrease. Newborns' appetitive oral behavior was the most reproducible response criterion to the effluvium of colostrum. In conclusion, a set of unidentified volatile compounds from human colostrum is robust enough after extraction from the original matrix and chromatographic processing to continue eliciting appetitive responses in neonates, thus opening new directions to isolate and assay specific volatile molecules of colostrum.

While sheep can detect and discriminate human emotions through visual and vocal cues, their reaction to human body odors remains unknown. The present study aimed to determine whether sheep (Ovis aries) can detect human odors, olfactorily discriminate stressed from non-stressed individuals, and behave accordingly based on the emotional valence of the odors. Axillary secretions from 34 students were collected following an oral examination (stress odor) or a regular class (non-stress odor). Fourteen female and 15 male lambs were then exposed to these odors through a habituation-dishabituation procedure. The habituation stimulus was presented four times for one minute, followed by the dishabituation stimulus presented once for one minute. Behavioral variables included spatiality relative to target odors, approach/withdrawal, ear positioning, sniffing, ingestion, and vocalization. Both female and male lambs more often positioned their ears backwards/forwards, and asymmetrically when exposed to the dishabituation stimulus, but regardless of their stress or non-stress value. They also changed their approach behavior when exposed to the dishabituation stimuli. Lambs displayed some behavioral signs of discrimination between the habituation and dishabituation odors, but regardless of their relation to stress or non-stress of human donors. In sum, this exploratory study suggests that young sheep respond negatively to the odor of unfamiliar humans, without showing any specific emotional contagion related to the stress odor. This exploratory study suggests young ovines can detect human body odor, a further step toward understanding the human-sheep relationship.

Odorant compounds that mammalian females ingest during pregnancy/lactation permeate to their perinatal offspring, impinging on progeny’s developing chemoreception and shaping subsequent preferences and behaviour. Long-term effects of these earliest experience have been repeatedly found with single flavour qualities, which induce postnatal selectivity in increasing preferences or reducing aversions. The two studies presented here attempted to go a step further with the laboratory mouse as model. Study 1 aimed examining whether prenatal only, postnatal only, or pre- and postnatal (transnatal) exposures to a single flavour through gestating/lactating dams’ drinking water orients differentially selective responsiveness for that flavour. While perinatal exposure to the flavour appeared to affect positively its exploration by 6-day-old pups, only post and transnatal exposure modified its consumption in drinking flavoured water after weaning. Study 2 aimed to go beyond exposure to a single flavour in assessing whether experiencing prenatally or postnatally a variety of flavours can influence later non-selective responsiveness to chemosensory and visual novelty. Specifically, weanling mice born to pregnant/lactating dams fed a regimen of flavour variety will be compared with weanlings exposed to a control regimen of flavour monotony. ‘Chemo-variety’ exposure consisted in odourising gestating/lactating dams’ drinking water with six flavourants changed every other day over a period of 6 days before or after birth. Control gestating/lactating dams were offered non-flavoured water. After weaning, offspring of both groups were tested for differential reactivity to novel olfactory or visual environments. While perinatal exposure to chemo-variety appeared to somehow affect ‘anxious’ reactivity and neophobic behaviour in weanlings, ingestion neophobia appeared relatively insensitive to early experience. Some sex differences emerged in these conditions, with females appearing more sensitive to the impact of perinatal chemosensory enrichment.

Bird behaviour toward sunflower crops is poorly understood in field conditions. The strategy used here, associating conditioned chemosensory aversion with seeds of a given colour, was run in three steps. Step 1 assessed birds' reactivity to visually and chemosensorily manipulated sunflower seeds. Six feeders of coloured seeds (blue, yellow, green, red, pink, control) were placed on two plots visited by birds. One week later, the birds were exposed to 3 feeders of differently flavoured seeds (methyl anthranilate (MA), d-pulegone, control). In both conditions, seed intake was recorded for 48 hours. Only Great Tits and Oak Jays came to the feeders. The least consumed seeds were those coloured blue (C) and flavoured with MA (R). Step 2 aimed to engage chemosensory aversion to flavoured and coloured (RC) sunflower seeds presented on the ground for 2 weeks before the actual sowing of sunflower. At step 3, sunflower was sawn in 4 modalities of seeds [coloured and flavoured (RC), coloured only (C), flavoured only (R), neither coloured, nor flavoured (T)] and bird behaviour and crop damage were monitored from sowing to emergence. It came out that seed treatments reduced corvid and pigeon frequentation of C and RC micro-plots and seed intake before germination. However, once the emergence stage was reached, none of the treatments seemed to significantly protect seedlings from birds. These trials appear to confirm that Rooks, Crows, and Pigeons are sensitive to the colour and aroma of sunflower seeds.

Mammalian newborns depend on their mother's milk to satisfy their initial needs of protection and nutrition. They reach the source of milk in following visual, tactile and olfactory cues. In particular, parturient ewes produce an odorous wax in the inguinal glands close to the teats. When presented separately to newly born lambs, this inguinal wax (IW) elicits arousal, head orientation, licking and increased respiratory rate indicative of their avidity for it. The present study assessed whether transferring IW into the environment of artificially fed lambs would improve their responses to the novelty of the situation. We first assessed whether suckled lambs preferred an IW-scented teat to a scentless control teat. Then, we assessed whether a teat odorized with IW was more easily learned as suckable relative to a control teat. Finally, the lambs' growth performance from postnatal days (PND) 0 and 20 was compared in groups reared with or without IW spread on the milk-feeder in their home pen. The behavioral assays did not evidence any significant effect of IW odor on previously suckled lambs' attraction and appetence responses. However, relative to the scentless control condition, being exposed to an IWsmeared milk-feeder led to a higher body weight at 20 days after birth. In the conditions of the present study, namely after suckling initiation, IW odor appeared not to be a strong determinant of short-term attraction or appetitive behavior in neonate lambs. The continued presence of IW, a familiar odor, in the artificial suckling context may improve artificially-reared lambs' emotional state that may affect their weight gain.

Olfactory cues of individuals of the same species or from different species may induce changes in behaviors and physiological reactions in mammals. However, there are few studies on the influence of human odor on animal behavior and welfare, especially those of rodents and farm animals. The present study aimed to investigate whether the odor of a stressed human (in sweat) would modify the behavior of mice and cows. We hypothesized that laboratory and farm animals can perceive human emotions though olfactory cues and that human emotional chemosignals can modify their behavioral reactions and welfare. Two odors of human axillary sweat were collected from engineering students (n = 25, 14 females and 11 males; 21.1 ± 0.7 years old, range: 19–23 years old): a “stress” odor collected after an exam and a “non-stress” odor collected after a standard class. Two experiments were then conducted to test the discrimination of these two odors by male mice (n = 20) under standard conditions and by cows (n = 10) under farm conditions. During the experiments, the behavioral responses of the animals to both odors (through a dispenser for the mice and a bucket for the cows) were observed. The mice produced significantly (p = 0.004) more fecal pellets with the stress odor dispenser than with the non-stress-odor dispenser. The cows spent significantly (p = 0.04) more time smelling the non-stress-odor bucket than control. For both species, the other behaviors observed did not differ significantly between the odors. Mice and cows seemed to perceive and react to stressful human chemosignals. Mice showed physiological reactions that indicated stress in response to the stress odor of humans, while cows showed preference reactions in response to the non-stress odor of humans. This preliminary study showed that laboratory and farm animals, such as male mice and cows, seemed to discriminate certain odors emitted by humans that were likely related to different emotions. Animals may recognize stressful human chemosignals, associate these signals with negative husbandry practices or human–animal relationships, and consequently modify their behavior.

Background: We recently demonstrated that chronic dietary exposure to a mixture of pesticides at low-doses induced sexually dimorphic obesogenic and diabetogenic effects in adult mice. Perinatal pesticide exposure may also be a factor in metabolic disease etiology. However, the long-term consequences of perinatal pesticide exposure remain controversial and largely unexplored. Objectives: Here we assessed how perinatal exposure to the same low-dose pesticide cocktail impacted metabolic homeostasis in adult mice. Methods: Six pesticides (boscalid, captan, chlopyrifos, thiachloprid, thiophanate, and ziram) were incorporated in food pellets. During the gestation and lactation periods, female (F0) mice were fed either a pesticide-free or a pesticide-enriched diet at doses exposing them to the tolerable daily intake (TDI) level for each compound, using a 1:1 body weight scaling from humans to mice. All male and female offsprings (F1) were then fed the pesticide-free diet until 18 weeks of age, followed by challenge with a pesticide-free high-fat diet (HFD) for 6 weeks. Metabolic parameters, including body weight, food and water consumption, glucose tolerance, and urinary and fecal metabolomes, were assessed over time. At the end of the experiment, we evaluated energetic metabolism and microbiota activity using biochemical assays, gene expression profiling, and H-1 NMR-based metabolomics in the liver, urine, and feces. Results: Perinatal pesticide exposure did not affect body weight or energy homeostasis in 6- and 14-week-old mice. As expected, HFD increased body weight and induced metabolic disorders as compared to a low-fat diet. However, HFD-induced metabolic perturbations were similar between mice with and without perinatal pesticide exposure. Interestingly, perinatal pesticide exposure induced time-specific and sex-specific alterations in the urinary and fecal metabolomes of adult mice, suggesting long-lasting changes in gut microbiota. Conclusions: Perinatal pesticide exposure induced sustained sexually dimorphic perturbations of the urinary and fecal metabolic fingerprints, but did not significantly influence the development of HFD-induced metabolic diseases.

Colostrum is the initial milk secretion which ingestion by neonates warrants their adaptive start in life. Colostrum is accordingly expected to be attractive to newborns. The present study aims to assess whether colostrum is olfactorily attractive for 2‐day‐old newborns when presented against mature milk or a control.

The nipple odor of lactating mice (Mus musculus) plays a crucial role in attracting newborn pups and motivating them to suck milk. The characteristic odor of a lactating murine nipple is assumed to be a mixture of multiple odorous substrates, that is, milk, dam's and pups' saliva, skin glands' secretions, and amniotic fluid. The present study aimed to characterize the behavioral activity of the original odor mixture that develops over the nipples in the first 2 days postpartum. We extracted this odor mixture in water and evaluated its attractive and appetitive potencies using two behavioral assays (viz., relative attraction and oral activation assays). It resulted that the so-called nipple wash was as appetitive as fresh milk, and even more attractive than it. The behavioral potency of the nipples was shown to be specific to lactating nipples (relative to nulliparous nipples) and to be preserved for 2 weeks when stored at -80°C. Finally, we perfected a nipple deodorization procedure by inactivating the nipples' behavioral potency. We observed that such altered appetitive potency was fully restored 30 min after its washing, but without any maternal self-licking and pups' sucking, indicating that the secretions of the nipple skin glands' were sufficient to explain the success of neonatal guidance to the nipple.

Murine milk conveys an odor factor that is both attractive and appetitive to conspecific newborns. Up to now, little is known about the temporal dynamic of this odor factor and about the stability of its behavioral activity after milk ejection. We aim to characterize the conditions in which the attractive and appetitive potency of milk to newborns is best conserved and, as a logical outcome, at standardizing conditions in which milk varies in reactogenic potency for newborns. Milk was collected and conserved in two conditions of cold (4 degrees C, - 80 degrees C) for several durations (3 and 24 h, and 1, 2 and 8 months). The reactogenic potency of milk was assayed in 2 day-old mouse pups. We found that milk remains olfactorily attractive and appetitive to newborns after 3 h of storage at 4 degrees C, but it completely loses reactogenic potency on newborn pups after 24 h of storage at 4 degrees C. Storage at - 80 degrees C preserves the behavioral activity of milk up to 1 month, but milk stored for 2 months at this temperature remains appetitive but not attractive to pups. Finally, the reactogenic potency of murine milk in pups is abolished after 8 months of storage at - 80 degrees C. This study highlights that attractive and appetitive factors of milk appear dissociable and, in any case, highly labile. It provides, for two different storage temperatures, a temporal window in which milk remains behaviorally active on pups. These results will allow designing a contrastive chemical approach to identify the reactogenic compounds of milk.

In the course of evolution, human mothers have been, and still are, under strong selective pressure to induce their newborns’ colostrum ingestion promptly after birth. As a concentrate of nutrients, passive immunity, antioxidants, growth factors and symbiotic microbiota, colostrum functions as the evolved antidote to ubiquitous pathogens and threats of neonatal exhaustion. Under such constraints, any means to speed up colostrum/milk intake can only have been beneficial to neonatal viability and adaptive life onset along evolutionary time. The areolar-nipple areas of human lactating females emit lacteal substrates conveying chemostimuli that are attractive and release mouthing and sucking in infants. Current information about areolar glands of Montgomery is summarized here, in terms of variability/regularity in number and distribution, of behavioural activity of their secretion, and of the adaptive value of their occurrence. It is concluded that a majority of lactating women investigated so far bear from 1 to >40 glands/areola, among which some emit a visible secretion. Reciprocally, a majority of neonate infants react to the odour of these secretions. The number of areolar glands correlates with infants’ behaviour at the breast, indicating that areolar phenotypic variability has potential fitness consequences on the infant and the mother. Ideas for future studies are outlined to advance our understanding of how human areolar phenotypic variability relates to life history characteristics.

Newborn mice are attracted to mammary odor cues carried in murine milk and nipple secretions. However, murine milk odor is not equally attractive along lactation. The present study focuses on the differential response of 2day-old mouse pups of C57Bl/6 (C) and Balb/C (B) strains to the odor of milk (Experiment 1) and nipples (Experiment 2) that are matched/unmatched in terms of pup's age or strain. In Experiment 1, C and B pups were tested in a series of tests simultaneously opposing either murine milk and a blank (water), or two milks collected in early and late lactation (lactation days 2 and 15, respectively) from females belonging to their own or the other strain. Results showed that C and B pups were attracted to the odor of the different milks regardless of the lactation age and the strain of the donor female. Nevertheless, C and B pups preferred the odor conveyed by early- than late-lactation milk of either strain. Moreover, early-lactation milk from C females was more attractive than early-lactation milk from B females for pups of either strain. In Experiment 2, differential nipple grasping response of C and B pups was measured when they were exposed to nipples of females in early or late lactation. The proportion of C pups that grasped a nipple was greater when they were exposed to a nipple in early lactation regardless of the strain of the donor females, whereas the proportion of B pups that grasped a nipple was greater when they were exposed to a nipple in early lactation, but only from own strain. Thus, newborn mice prefer the odor of milk and nipples from females that are matched in lactation age. This result is discussed in terms of reciprocally adaptive mechanisms between lactating females and their newborn offspring.