Mother-young relationships in sheep: a model for a multidisciplinary approach of the study of attachment in mammals

Bison mother-offspring acoustic communication

Mother-offspring communication is especially crucial for social species in order to synchronize activities essential for early survival including nursing, resting, maintaining proximity during group movements between food or water sources, and locating one another if separated in a large social group. One of the most social ungulate species in North America is the American Bison (Bison bison), formerly known as buffalo. Adult female bison associate with their young for over a year and communication between mother and offspring is likely essential for establishing and maintaining a bond upon which the life of a calf depends. One goal of this study was to quantify and compare the acoustic form of vocalizations of adult female, subadult, and calf bison and to determine how age classes differed in call structure. The other goal was to identify the contexts in which bison vocalized. Vocalizations of 101 bison (53 adult females, 15 subadults, 33 calves) in a semi-free-ranging herd in Montana were analyzed and found to be pulsatile sounds, unlike vocalizations of bison bulls or domestic cows and calves. Vocalizations of bison cows, subadults, and calves differed significantly in total duration, numbers of pulses, pulse duration, and pulse rate. Seven distinct call contexts were identified. The majority of calls were "moving-on calls" (39%), when a cow called and her calf ran to her side and the 2 moved on together, and "contact calls" (21%) when a cow called and her calf called back but neither changed their location. "Imprinting calls" and "nursing calls" were also identified. Mother-offspring acoustic communication in bison appears especially critical for coordinating movements. Understanding the role of acoustic communication in maintaining the bond between bison mothers and their offspring can contribute to the humane management and welfare of this iconic species.

Temporary sensory separation of lamb groups from ewes affects behaviors and serum levels of stress-related indicators of small-tailed Han lambs

Under the current meat sheep breeding system, newborn lambs usually live with their mothers until weaning, and in daily management, they often need to be separated from their ewes for a short period due to dehorning, disease treatment, etc. Such short-term separation was considered to be a high-intensity stress for the lambs. This study aimed to explore the effects of 1 h sensory separations on behaviors and the concentration of stress-related indicators of small-tailed Han lambs. Lambs were assigned to four groups: auditory, visual, and tactile separation (AVT) group; visual and tactile separation (VT) group; tactile separation (T) group; and control (C) group. Then they were separated from their mothers for one hour on postnatal days 14, 21, 28, 35 and 42. Results showed the separated lambs (AVT, VT, and T groups) spent less time lying down relaxing and more time looking around, exploring, vocalizing, and attempting to escape (P < 0.05). Lambs separated by lack of tactile contact only exhibited the most escaping and moving behavior. Twin-born lambs showed less moving, escaping, and vocalizing than single-born lambs (P < 0.05). The separation also led to a rise in serum globulin levels and a decrease in tetraiodothyronine. In conclusion, this study showed that temporary 1 h ewe-lamb separations could affect behaviors and the serum levels of stress indicators of lambs. The behavioral responses were more obvious when lambs were separated by lack of tactile contact only, and in single-born lambs. It can conclude that indicated that when lambs need to be temporarily separated from ewes in daily management production, it would be better to let them stay together with their littermates, and make them avoid hearing or seeing the ewes, such management may partially reduce the separation stress, thereby improving the welfare and breeding efficiency of sheep.

Sensory Mechanisms of Parent-Offspring Recognition in Fishes, Amphibians, and Reptiles

Parental care is important for offspring survival and success. Recognition of offspring by parents is critical to ensure parents direct care behaviors at related offspring and minimize energy lost by caring for unrelated young. Offspring recognition of parents prevents possible aggressive interactions between young and unrelated adults and allows offspring to direct begging behaviors toward the correct adult. Despite its importance and widespread nature, much of the current research has focused on a small range of species, particularly mammals and birds. We review the existing literature on the sensory mechanisms of parent-offspring recognition in fishes, amphibians, and reptiles. Within these groups, there is diversity in the presence and strategies for parent-offspring recognition. Future studies should continue to identify these mechanisms, as well as the neural and endocrine underpinnings in non-model organisms to expand our knowledge of this behavior and inform our understanding of the evolution of parent-offspring recognition.

The Role of Oxytocin in Domestic Animal’s Maternal Care: Parturition, Bonding, and Lactation

Oxytocin (OXT) is one of the essential hormones in the birth process; however, estradiol, prolactin, cortisol, relaxin, connexin, and prostaglandin are also present. In addition to parturition, the functions in which OXT is also involved in mammals include the induction of maternal behavior, including imprinting and maternal care, social cognition, and affiliative behavior, which can affect allo-parental care. The present article aimed to analyze the role of OXT and the neurophysiologic regulation of this hormone during parturition, how it can promote or impair maternal behavior and bonding, and its importance in lactation in domestic animals.

Toward assessing the role of dietary fatty acids in lamb's neurological and cognitive development

Understanding and measuring sheep cognition and behavior can provide us with measures to safeguard the welfare of these animals in production systems. Optimal neurological and cognitive development of lambs is important to equip individuals with the ability to better cope with environmental stressors. However, this development can be affected by nutrition with a special role from long-chain fatty acid supply from the dam to the fetus or in lamb's early life. Neurological development in lambs takes place primarily during the first two trimesters of gestation. Through late fetal and early postnatal life, the lamb brain has a high level of cholesterol synthesis. This rate declines rapidly at weaning and remains low throughout adulthood. The main polyunsaturated fatty acids (PUFA) in the brain are ω-6 arachidonic acid and ω-3 docosahexaenoic acid (DHA), which are elements of plasma membranes' phospholipids in neuronal cells. DHA is essential for keeping membrane integrity and is vital for normal development of the central nervous system (CNS), and its insufficiency can damage cerebral functions and the development of cognitive capacities. In sheep, there is evidence that supplying PUFA during gestation or after birth may be beneficial to lamb productive performance and expression of species-specific behaviors. The objective of this perspective is to discuss concepts of ruminant behavior and nutrition and reflect on future research directions that could help to improve our knowledge on how dietary fatty acids (FA) relate to optimal neurological and cognitive development in sheep.

Serum Oxytocin, Cortisol and Social Behavior in Calves: A Study in the Impossible Task Paradigm

In this study, we explored the correlations between circulating levels of oxytocin, cortisol, and different social behaviors toward humans in 26 Italian Red Pied calves (all females, with an average age of 174 ± 24 days) using the impossible task paradigm. This paradigm has proved fruitful in highlighting the effect of socialization on the willingness to interact with humans in several domesticated species. The test consists of the violation of an expectation (recovering food from an experimental apparatus) while a caregiver and a stranger are present. Immediately after the end of the test (less than one minute), blood was collected from the coccygeal vein. Statistics were performed by the Spearman's rank correlation; significant differences were adjusted according to Bonferroni's correction. Cortisol correlates positively (ρ = 0.565; p < 0.05) with the latency of behaviors directed at the caregiver, and the duration of behaviors directed at the apparatus correlates negatively with both the caregiver (ρ = -0.654; p < 0.05) and a stranger (ρ = -0.644; p < 0.05). Contrary to what is reported in the literature on cows, no correlations were found between oxytocin levels and direct behaviors toward the caregiver. This highlights a different behavioral strategy between calves and cows when placed in front of an impossible task.

Mother-Young Bonding: Neurobiological Aspects and Maternal Biochemical Signaling in Altricial Domesticated Mammals

Mother-young bonding is a type of early learning where the female and their newborn recognize each other through a series of neurobiological mechanisms and neurotransmitters that establish a behavioral preference for filial individuals. This process is essential to promote their welfare by providing maternal care, particularly in altricial species, animals that require extended parental care due to their limited neurodevelopment at birth. Olfactory, auditory, tactile, and visual stimuli trigger the neural integration of multimodal sensory and conditioned affective associations in mammals. This review aims to discuss the neurobiological aspects of bonding processes in altricial mammals, with a focus on the brain structures and neurotransmitters involved and how these influence the signaling during the first days of the life of newborns.

Postnatal maternal behaviour expression depends on lambing difficulty in Merino ewes

Dystocia, a prolonged or non-progressive birth event, is the main contributor to lamb mortality in Australia and across the world. Dystocia can cause neonatal hypoxia, central nervous system (CNS) damage leading to increased risk of starvation, exposure and mismothering, and death. These prolonged birth events can also cause fatigue, injury and death in the ewe. Dystocia may interrupt the expression of maternal behaviour and the strength of the ewe-lamb bond, and consequently lamb survival. This study focused on the effect of dystocia on ewe behaviour in the 2 h post-lambing. A total of 18 ewes were chosen for continuous behaviour annotation and analysis (dystocic (n = 9) and eutocic (n = 9)) based on the quality of video recordings, length of stage 2 parturition and classification by a single experienced observer. Dystocic ewes showed significantly lower expression of maternal behaviours and a significantly greater expression of avoidance behaviours compared to eutocic ewes. Additionally, dystocic ewes performed fewer behaviours in total compared to eutocic ewes. Dystocia can significantly affect the quality and quantity of ewe maternal behaviour expression, leading to increased avoidance of the lamb, increased risk of maternal disinterest, and increased risk of death for the lamb. If dystocic events can be identified quickly and accurately, measures can be taken to ensure the ewe and lamb recover successfully.

Serum Oxytocin in Cows Is Positively Correlated with Caregiver Interactions in the Impossible Task Paradigm

Simple Summary

A possible relationship between circulating hormones (e.g., oxytocin and cortisol) and social behaviors toward humans in cows was studied using the impossible task paradigm test. Serum oxytocin levels correlated positively with the duration and negatively correlated with the latency of the cows’ social interactions with the caregiver. The implications of these findings for productivity as well as for animal welfare can be numerous and worth further investigation.

Abstract

This study explored a possible relationship between the circulating oxytocin, cortisol, and the willingness of dairy cows to engage in social behaviors with humans in an experimental context. The behaviors of twenty-nine cows were recorded during the impossible task paradigm, a procedure aimed at creating a violation of expectancy, in the presence of the caregiver and a stranger. The results showed that serum oxytocin levels were positively correlated with duration and negatively correlated with the latency of the cows’ social interactions with the caregiver. This research provides a clear correlation between circulating oxytocin and a willingness to engage in social contact with the caregiver, excluding the possible effect of different cortisol levels on such behavior.

The Onset of Maternal Behavior in Sheep and Goats: Endocrine, Sensory, Neural, and Experiential Mechanisms

In sheep and goats, the onset of maternal behavior at parturition is characterized by a first phase called maternal responsiveness during which the mother is attracted to any newborn. In a second phase, called maternal selectivity, the mother establishes a selective bond with her young so that she only accepts it at suckling. After a description of the behavioral expression of both phases, this chapter reviews the physiological, sensory, and neural mechanisms involved. These two behavioral processes are synchronized with parturition by the vaginocervical stimulation induced by the expulsion of the newborn. Olfactory cues provided by the neonate are involved in maternal responsiveness and selectivity. Oxytocin supported by estrogens is the key factor for maternal responsiveness. The neural network involved in maternal responsiveness is mainly hypothalamic and is different from the circuitry involved in selectivity, which mainly concerns olfactory processing regions. Visual and auditory cues are necessary for offspring recognition at a distance. This multisensory recognition suggests that mothers form a mental image of their young. Maternal experience renders mothers more responsive to maternally relevant physiology and to young-related sensory inputs.

Regulation of maternal behavior, social isolation responses, and postpartum estrus by steroid hormones and vaginocervical stimulation in sheep

Periparturient ewes display several activities in addition to maternal behavior per se. They isolate themselves from the flock and, contrary to other mammals, do not show postpartum estrus. We investigated the possibility of a common hormonal control of maternal behavior, prepartum social isolation responses, and absence of postpartum estrus. We quantified responses to flockmate separation and incidence of sexual receptivity at several reproductive stages in intact ewes (Experiment 1). Responses to social isolation were lowest in preparturient ewes and at pregnancy day 149, intermediate at pregnancy day 147 and highest at day 136 and in non-pregnant ewes (P < 0.05 between the 3 levels). In a second experiment, we quantified the same parameters and maternal behavior in 1) ovariectomized ewes receiving medroxyprogesterone acetate only (ovxMPA); 2) ovariectomized ewes receiving MPA + estradiol benzoate (ovxSHORT); 3) intact ewes receiving a longer MPA + estradiol dipropionate treatment, before and after vaginocervical stimulation (VCS). Before VCS no steroid treatments decreased social isolation responses and maternal behavior was scarce or absent. Following VCS and interaction with lamb, maternal responses in the ovxSHORT group increased while social isolation responses decreased. Sexual receptivity occurred in non-pregnant ewes and in ovxSHORT group. Conclusion: some hormonal treatments +VCS can effectively induce maternal behavior and reduce social isolation responses. Long-term progestin treatment can inhibit postpartum estrus.

Mammary Gland Structures Are Not Affected by an Increased Growth Rate of Yearling Ewes Post-Weaning but Are Associated with Growth Rates of Singletons

The experiment aimed to examine the impacts of an increased growth rate of ewes between three and seven months of age on udder development using ultrasound and to establish whether ultrasonography could be used to identify ewe mammary structures that may be indirect indicators of singleton growth to weaning. Udder dimensions, depths of gland cistern (GC), parenchyma (PAR) and fat pad (FP) were measured in late pregnancy (P107), early lactation (L29), and at weaning (L100) in 59 single-bearing yearling ewes selected from two treatments. The 'heavy' group (n = 31) was preferentially fed prior to breeding achieving an average breeding live-weight of 47.9 ± 0.38 kg at seven months of age. The 'control' group (n = 28) had an average breeding live-weight of 44.9 ± 0.49 kg. Udder dimensions, GC, PAR and FP did not differ between treatments. Lamb growth to L100 was positively associated (p < 0.05) with PAR at P107 and GC at L29. There was no evidence of negative effects of the live-weight gain treatments on udder development of yearling ewes as measured by ultrasonography. The results suggest that this ultrasound method has the potential to identify pregnant yearling ewes which would wean heavier singletons.

Dam parity and calf sex affect maternal and neonatal behaviors during the first week postpartum in stabled Maghrebi dairy camels

Currently, a trend toward the commercialization of dromedary milk associated with recent intensive rearing systems has starting worldwide which impose constraints on animals affecting their behavioral repertoires and welfare status. The aim of this study was to investigate the effects of dam parity and calf sex on parturition, neonatal, and maternal behaviors in stabled Maghrebi dairy camels (Camelus dromedarius). Thirty-six (primiparas N = 10; multiparas N = 26) periparturient females were kept under video surveillance using a digital IR camera and 24-h sessions were chosen to assess calving, maternal, and neonatal behaviors in calving pens. Duration of restlessness, process of giving birth, and expulsion of fetal membranes were assessed. After first suckling, dams and their calves were moved into an individual enclosure to assess maternal behavior at 12 h, 24 h, 48 h, 72 h, and 7d postpartum. Behavior was assessed using a camcorder for 30 min after 1 h of young separation in an adjacent enclosure. Results showed an effect of parity on the duration of the birth process which was longer for primiparous than multiparous camels (P = 0.034). During this stage, primiparous females tended to raise their tails more often (P = 0.054) and spent more time standing (P = 0.001) than multiparous camels. Neonatal behavior was affected by calf sex. Female newborns took less time to raise their heads (P = 0.041) and to stand up (P = 0.048) for the first time and were the earliest to suckle their dams (P = 0.032). Multiparous dams stood up sooner (P = 0.019) after calving and suckled their calves earlier (P = 0.043) than primiparous dams. They emitted more bleats and exhibited more sniffing during the first week postpartum than primiparas. During the first postpartum week, both primiparas and multiparas showed a decrease in the total number of bleats (P < 0.001), low-pitch bleats (P < 0.001), and high-pitch bleats (P < 0.001), in sniffing frequency (P < 0.001) and sniffing duration (P < 0.001). This is the first study to describe in detail the calving, maternal, and neonatal behaviors of dromedary camels and to show the influence of parity and calf sex. Maternal care toward the newborn calf exhibited by a high level of bleating and sniffing activities in the first 2 days suggest that they play an important role in the establishment of mother-young relationship.

Neonatal Suckling, Oxytocin, and Early Infant Attachment to the Mother

The neuropeptide oxytocin (OT) promotes maternal care and social affiliation in adults but its importance in infant attachment still remains unknown. True animal models of infant attachment are extremely rare, and the sheep (in complement to non-human primates) is one of the few that provides the opportunity to investigate its neuroendocrinological basis. In the lamb, access to the udder has strong rewarding properties for the establishment of a preferential relationship with the mother. Therefore, the present study explored the possible involvement of OT through its release during close social contacts with the mother. The first experiment revealed that lambs having free access to the udder from birth onward developed, by 12 h of age, a clear preference for their mothers over another maternal ewe. Delaying access to the udder for six, four or even only 2 h starting at birth, by covering the ewe's udder, resulted in the lack of such a preference without affecting general activity. These effects persisted in most cases at 24 h but by 72 h of age a bond with the mother was clearly expressed. Experiment two showed that social interactions with the mother were followed by a release of OT in the plasma when lambs had the possibility to suckle. Non-nutritive interactions were without effects. Preliminary data on two subjects suggested that OT might also increase in the cerebrospinal fluid after suckling. Finally, in the third experiment, oral administration of a non-peptide OT receptor antagonist (L-368-899, Merck) over the first 4 h after birth led to decreased exploration of the mother's body compared to lambs receiving saline, and impaired the expression of a preference for the mother at 24 h. The effects were no longer observed at 48 h. Our findings demonstrate that both delayed access to the mother's udder and OT receptor antagonist alter the onset of mother preference in newborn lambs. This suggests that central OT facilitates the development of filial attachment through its release during suckling.

Intranasal oxytocin affects the stress response to social isolation in sheep

Oxytocin (OT) is a neuropeptide hormone that modulates several social behaviors and can affect the anxiety and stress response. The aim of this study was to determine if administration of intranasal OT affects the stress response to social isolation in sheep. Twenty adult Merino ewes were assigned to two groups; 1) Control group (CG, n = 10), which received an intranasal administration of isotonic saline and 2) Oxytocin-treated group (OTG, n = 10), which received an intranasal administration of OT (24 IU) 40 min before the animals were placed in the social isolation test. During the social isolation test (10 min), the behavior of the sheep was recorded, and blood samples were obtained before and after the test for the determination of cortisol, glucose and serum proteins, and heart rate and surface temperature were recorded. The OTG ewes had a higher cortisol concentration (P = 0.04) after social isolation, tended to vocalize more (P = 0.06) during isolation, and tended to have lower globulin concentrations (P = 0.10) than the CG ewes. Contrary to what we expected, the administration of intranasal OT increased the stress response to social isolation in ewes, which was evidenced by endocrine (greater increase in cortisol concentration), physiological (a tendency to present lower concentration of globulins in blood) and behavioral (a tendency to vocalize more) indicators. This study suggests that the administration of intranasal OT increased the stress response to isolation possibly by strengthening the social bond among ewes.

Communication is key: Mother-offspring signaling can affect behavioral responses and offspring survival in feral horses (Equus caballus)

Acoustic signaling plays an important role in mother-offspring recognition and subsequent bond-formation. It remains unclear, however, if mothers and offspring use acoustic signaling in the same ways and for the same reasons throughout the juvenile stage, particularly after mutual recognition has been adequately established. Moreover, despite its critical role in mother-offspring bond formation, research explicitly linking mother-infant communication strategies to offspring survival are lacking. We examined the communicative patterns of mothers and offspring in the feral horse (Equus caballus) to better understand 1) the nature of mother-offspring communication throughout the first year of development; 2) the function(s) of mother- vs. offspring-initiated communication and; 3) the importance of mare and foal communication to offspring survival. We found that 1) mares and foals differ in when and how they initiate communication; 2) the outcomes of mare- vs. foal-initiated communication events consistently differ; and 3) the communicative patterns between mares and their foals can be important for offspring survival to one year of age. Moreover, given the importance of maternal activity to offspring behavior and subsequent survival, we submit that our data are uniquely positioned to address the long-debated question: do the behaviors exhibited during the juvenile stage (by both mothers and their young) confer delayed or immediate benefits to offspring? In summary, we aimed to better understand 1) the dynamics of mother-offspring communication, 2) whether mother-offspring communicative patterns were important to offspring survival, and 3) the implications of our research regarding the function of the mammalian juvenile stage. Our results demonstrate that we have achieved those aims.

On the Nature of the Mother-Infant Tie and Its Interaction With Freudian Drives

The affective bond between an infant and its caregiver, the so-called mother-infant tie, was analyzed by various reputable psychologists (e.g., Ainsworth, Clark, Erikson, Anna Freud, Harlow, Klein, Spitz, and Winnicott) but both the basic tenets of the bond and the importance of the trauma of maternal deprivation for personality disorders in adults were introduced by Bowlby. Although Bowlby was a trained psychoanalyst, he rejected central cornerstones of Freudian theory (esp. drive theory) and used concepts promulgated by renowned ethologists (Tinbergen and Lorenz) to establish his framework of "instinctive behavior" that has been developed further into the concept of "attachment theory" under the influence of Mary Ainsworth. However, since any precise experimental facts were lacking when Bowlby formulated his ideas on the concept of instinctive behavior, the whole framework is a descriptive, category-driven approach (like the ones of Freudian drives). In order to connect the mother-infant tie - as propounded by Bowlby - with experimental data, this manuscript undertakes a biochemical analysis of it because this strategy proved somewhat successful in relation to Freudian drives. The analysis unfolded that the neurochemical oxytocin, released by the action of sensory nerves, is of utmost importance for the operation of the mother-infant tie. Furthermore, multiple evidences have been presented to the fact that there is strong interaction between unconsciously operating Freudian drives and the consciously acting mother-infant tie (that is now classified as a drive). The outlined interaction in conjunction with the classification of attachment urges as drives gave a very detailed insight into how a SEEKING-derived reward can be evoked during operation of the mother-infant tie. In summary, there is no need to marginalize either the mother-infant tie or Freudian drives but rather there is need to respect both (principally different) impulses in moving toward a more extensive description.

The parental brain and behavior: A target for endocrine disruption

During pregnancy, the sequential release of progesterone, 17β-estradiol, prolactin, oxytocin and placental lactogens reorganize the female brain. Brain structures such as the medial preoptic area, the bed nucleus of the stria terminalis and the motivation network including the ventral tegmental area and the nucleus accumbens are reorganized by this specific hormonal schedule such that the future mother will be ready to provide appropriate care for her offspring right at parturition. Any disruption to this hormone pattern, notably by exposures to endocrine disrupting chemicals (EDC), is therefore likely to affect the maternal brain and result in maladaptive maternal behavior. Development effects of EDCs have been the focus of intense study, but relatively little is known about how the maternal brain and behavior are affected by EDCs. We encourage further research to better understand how the physiological hormone sequence prepares the mother's brain and how EDC exposure could disturb this reorganization.

Imprinting of a Nonpheromonal Cue and Its Protective Effect on Alien Male-Induced Implantation Failure in Mice

Bruce effect or alien male-induced implantation failure is a well-studied phenomenon in mice. The presence of stud male during exposure to an alien male protects the female from implantation failure. The pheromones of the stud male are imprinted in the female at the time of mating and act as a luteotrophic agent. We tested whether a nonpheromonal cue exposed to the female during pericopulatory sensitive period could protect pregnancy in newly inseminated females exposed to alien males. Virgin females were allowed to mate in the presence of a cotton ball smeared with groundnut oil as a nonpheromonal cue. When these females were exposed to alien males in the presence of groundnut oil, the majority of the females retained their pregnancy. We evidenced that a nonpheromonal cue could possibly protect the female from alien male-induced implantation failure. The majority of the females exposed to the nonpheromonal cue during the pre-or postcopulatory interactions with the males, exhibited higher rate of pregnancy failure on reexposure to the same cue at the time of exposure to alien males. The protective effect of the nonpheromonal cue is observed only when the female is exposed to it during the pericopulatory sensitive period.

Flawed mothering or infant signaling? The effects of deficient acoustic cues on ovine maternal response

The neonate distress cry, which displays a similar acoustic structure across a range of mammalian species, is highly effective in attracting, even compelling, parental care. However, if this cry is defective, as found in human and rodent neonates with poor neurobehavioral function, is the signal less enticing? Using playback recordings of a ewe's own co-twins as stimuli in a two choice test, we compared the preference of each sheep dam for acoustic features of lamb distress calls to assess the impact of signal quality on maternal response. The results of this study indicate that lamb vocalizations with acoustic parameters reflecting poor vocal fold engagement and arousal were less likely to be preferred by their dam. Additionally, these calls were associated with delayed vocal initiation and poor infant survival behavior suggestive of subtle cognitive deficit; and support the possibility that, as in deer and rodents, ovine vocalizations within a specific fundamental frequency range may well be a trigger for optimal maternal behavior. This research has important implications for understanding failed maternal-young interactions in ungulate and other species, and for verifying standardization of infant stimuli used in maternal behavior studies.

Maternal Odor Exposure Modulates Acceptance of a Bitter Taste in Newborn and Infant Rats

The acceptance of bitter, aversive, substances during early life is enhanced by stimulation with familiar, pre-exposed odors. Newborn rats exhibited heightened grasp responses toward an artificial nipple dispensing quinine, and drank more of this bitter solution, if concurrently stimulated with a lemon odor they had been exposed to shortly after birth. It yet unknown, however, if odors made familiar via normative developmental milestones also acquire modulatory influence upon seeking and intake of basic tastants. The current study assessed the influence of exposure to maternal odor on intake and grasp responses toward a surrogate nipple providing quinine, in 3-day (Experiment 1) or 12-day (Experiment 2) old, Wistar rat pups. The results revealed enhanced seeking and intake of the bitter solution, but not of water, in animals tested in the presence of the mother (and hence exposed to its odor cues), at both ages, compared to counterparts given either no explicit odor stimulation or stimulation to the odor of an unrelated dam. These results, obtained with a biologically relevant odor, are consistent with those previously found with a neutral, arbitrary odor. It seems that during the early stages of development, familiar odors regulate the acceptance of non-palatable, otherwise rejected, flavors.

Maternal care affects chicks' development differently according to sex in quail

Maternal behavior is known to influence the behavioral development of young. Recently, it was demonstrated that maternal behavior also differed according to sex of chicks and brood sex composition. So, here, we explored if these factors influenced behavioral development of quail chicks when they were brooded, and what characteristics of chicks and foster females could best explain this development. We studied three sets of chick pairs brooded by foster females: unisex male, unisex female, and mixed broods. We found that both emotivity profile and sociality depended on the sex: females were more reactive and less social than males. Females' emotivity profile was correlated with brood composition and foster female activity during maternal care. In males, only sociality was correlated with foster females' scores of aggressive rejection. Our results evidence that male and female chicks respond differentially to maternal behavior. This is discussed in terms of ecological and physiological constraints on development according to sex.

All bonds are not alike: A psychoendocrine evaluation of infant attachment

Characteristics of attachment were assessed in peer- and object-reared lambs, and compared to mothered subjects by taking into consideration distress, proximity seeking, and exploration during two separation-reunion tests in both the familiar and a novel environment. Plasma cortisol and oxytocin were assayed as physiological indicators of stress and being comforted during the separation-reunion test. Rewarding properties of the familiar figures were also determined in a conditioned place preference-like paradigm. Between-group analysis revealed the existence of secure attachment with the mother, alteration of secure attachment with the peer and weaker attachment with the object. Weaker attachment was expressed by a lack of distress during separation in the home pen and no preference for the place conditioned with the familiar object. Elevated basal plasma oxytocin levels, but not cortisol, observed in maternally deprived lambs were more likely linked to the absence of a maternal figure rather than social comfort during reunion.

Growing without a mother results in poorer sexual behaviour in adult rams

The aim of this study was to determine if the absence of the mother during rearing has long-term effects on sexual behaviour and physiological reproductive parameters of adult rams. Two groups of rams were: (1) artificially reared, separated from their dams 24 to 36 h after birth (Week 0) and fed using sheep milk until 10 weeks of age (group AR, n=14); and (2) reared by their dams until 10 weeks of age (group DR, n=13). Sexual behaviour (tests of 20 min) and physiological reproductive parameters were analysed separately for the non-breeding (Weeks 42 to 64) and the breeding (Weeks 66 to 90) seasons. Body weight, scrotal circumference, gonado-somatic index, testosterone concentrations or sperm parameters were similar in both rearing conditions (AR v. DR) in both seasons. During the non-breeding season AR rams displayed fewer ano-genital sniffings (AR: 4.2±0.4 v. DR: 5.3±0.4, P=0.04) and matings (AR: 1.2±0.2 v. DR: 1.8±0.2, P=0.002) than DR rams. During the breeding season AR rams displayed fewer ano-genital sniffings (AR: 4.3±0.5 v. DR: 5.7±0.5, P=0.005), flehmen (AR: 0.7±0.2 v. DR: 1.1±0.2, P=0.03), mount attempts (AR: 1.4±0.2 v. DR: 2.1±0.2, P=0.04), and tended to mount less frequently (AR: 6.6±0.9 v. DR: 8.8±0.9, P=0.08) than DR rams. In conclusion, the absence of the mother during the rearing period negatively affected display of sexual behaviour towards oestrous ewes during a rams adult life in both breeding and non-breeding seasons. However, it did not affect testis size, testosterone secretion or sperm variables.

Competition for oestrous ewes between rams reared by their mothers or artificially reared: Effects on sexual behaviour and testosterone and cortisol serum concentrations

The objective of this study was to determine how the social competition for an oestrous ewe affects the sexual behaviour and the endocrine response in two groups of rams, one reared by their mothers and another artificially reared. Thus, we compared the sexual behaviour and testosterone and cortisol changes in each group of rams in competitive and non-competitive tests, both during the first and second breeding seasons. Two groups of rams were: 1) artificially reared lambs, separated from their dams 24-36 h after birth (Week 0) and artificially fed with sheep milk until 10 weeks of age (group AR, n = 14); and 2) lambs reared by their dams until 10 weeks of age (group DR, n = 13). Rams were subjected to non-competitive and competitive tests for an oestrous ewe during their first and second breeding seasons, when they were 8 and 20 months old, respectively. Sexual behaviours toward an oestrous ewe were recorded during 20 min and the testosterone and cortisol concentrations were determined in serum samples collected immediately before the test, and 20, 40 and 60 min after it. During the first breeding season, the number of flehmen decreased in DR rams, and the number of flehmen and ano-genital sniffings also decreased in DR rams, but the frequency of some copulatory behaviours increased (matings and ejaculation/total mounts in DR rams, and total mounts in AR rams) in competitive tests. During the second breeding season, competition caused a decrease in the number of all the recorded behaviours (courtship and copulation) with the exception of flehmen in AR rams; however, in DR rams only the number of the copulatory behaviours decreased under competition. Competition did not affect the endocrine response during the first breeding season. During the second breeding season, while testosterone concentrations were greater in non-competitive than in competitive tests at 60 min (P = 0.0008) in AR rams, in DR rams it tended to be greater (P = 0.09). Competition did not affect cortisol concentrations in any group or season, but in all tests the concentrations increased at the end of the test (P < 0.05). In conclusion, the lack of the mother during rearing negatively affected the sexual motivation and the testosterone response of rams to oestrous ewes in competitive tests, effects that were more evident when adults. Neither the absence of the mother during rearing nor competition for oestrous ewes affected the stress response (evidenced by increase in cortisol concentration) in rams during both seasons.

Behavioral evidence of heterospecific bonding between the lamb and the human caregiver and mapping of associated brain network

While behavioral mechanisms of bonding between young mammals and humans have been explored, brain structures involved in the establishment of such processes are still unknown. The aim of the study was to identify brain regions activated by the presence of the caregiver. Since human positive interaction plays an important role in the bonding process, activation of specific brain structures by stroking was also examined. Twenty-four female lambs reared in groups of three were fed and stroked daily by a female caregiver between birth and 5-7 weeks of age. At 4 weeks, an isolation-reunion-separation test and a choice test revealed that lambs developed a strong bond with their caregiver. At 5-7 weeks of age, lambs were socially isolated for 90min. They either remained isolated or met their caregiver who stroked them, or not, at regular intervals over a 90-min period. Neuronal activation was investigated at the end of the period for maximum c-Fos expression. Reunion with the caregiver appeased similarly the lambs whether stroking was provided or not. Stroking did not activate a specific brain network compared to no stroking. In both cases, brain regions associated with olfactory, visual and tactile cue processing were activated in the presence of the caregiver, suggesting a multisensory process involved. In addition, activation of the oxytocinergic system in the hypothalamic paraventricular nucleus induced by the presence of the caregiver suggests similar neuroendocrine mechanisms involved in inter-conspecific and animal-human bonding.

Computation of a high-resolution MRI 3D stereotaxic atlas of the sheep brain

The sheep model was first used in the fields of animal reproduction and veterinary sciences and then was utilized in fundamental and preclinical studies. For more than a decade, magnetic resonance (MR) studies performed on this model have been increasingly reported, especially in the field of neuroscience. To contribute to MR translational neuroscience research, a brain template and an atlas are necessary. We have recently generated the first complete T1-weighted (T1W) and T2W MR population average images (or templates) of in vivo sheep brains. In this study, we 1) defined a 3D stereotaxic coordinate system for previously established in vivo population average templates; 2) used deformation fields obtained during optimized nonlinear registrations to compute nonlinear tissues or prior probability maps (nlTPMs) of cerebrospinal fluid (CSF), gray matter (GM), and white matter (WM) tissues; 3) delineated 25 external and 28 internal sheep brain structures by segmenting both templates and nlTPMs; and 4) annotated and labeled these structures using an existing histological atlas. We built a quality high-resolution 3D atlas of average in vivo sheep brains linked to a reference stereotaxic space. The atlas and nlTPMs, associated with previously computed T1W and T2W in vivo sheep brain templates and nlTPMs, provide a complete set of imaging space that are able to be imported into other imaging software programs and could be used as standardized tools for neuroimaging studies or other neuroscience methods, such as image registration, image segmentation, identification of brain structures, implementation of recording devices, or neuronavigation. J. Comp. Neurol. 525:676-692, 2017. © 2016 Wiley Periodicals, Inc.

Neural mechanisms of mother-infant bonding and pair bonding: Similarities, differences, and broader implications

This article is part of a Special Issue "Parental Care". Mother-infant bonding is a characteristic of virtually all mammals. The maternal neural system may have provided the scaffold upon which other types of social bonds in mammals have been built. For example, most mammals exhibit a polygamous mating system, but monogamy and pair bonding between mating partners occur in ~5% of mammalian species. In mammals, it is plausible that the neural mechanisms that promote mother-infant bonding have been modified by natural selection to establish the capacity to develop a selective bond with a mate during the evolution of monogamous mating strategies. Here we compare the details of the neural mechanisms that promote mother-infant bonding in rats and other mammals with those that underpin pair bond formation in the monogamous prairie vole. Although details remain to be resolved, remarkable similarities and a few differences between the mechanisms underlying these two types of bond formation are revealed. For example, amygdala and nucleus accumbens-ventral pallidum (NA-VP) circuits are involved in both types of bond formation, and dopamine and oxytocin actions within NA appear to promote the synaptic plasticity that allows either infant or mating partner stimuli to persistently activate NA-VP attraction circuits, leading to an enduring social attraction and bonding. Further, although the medial preoptic area is essential for maternal behavior, its role in pair bonding remains to be determined. Our review concludes by examining the broader implications of this comparative analysis, and evidence is provided that the maternal care system may have also provided the basic neural foundation for other types of strong social relationships, beyond pair bonding, in mammals, including humans.

Construction of an MRI 3D high resolution sheep brain template

Sheep is a developing animal model used in the field of neurosciences for the study of many behavioral, physiological or pathophysiological mechanisms, including for example, the central control of social behavior, brain injury or neurodegenerative diseases. However, sheep remains an orphan species in the field of magnetic resonance imaging (MRI). Therefore, a mean image (template), resulting of registrations of multiple subject images is needed and currently does not exist. In this study, we: i) computed multimodal high resolution 3D in-vivo sheep brain templates of T1 weighted (T1W) and T2W images, ii) computed gray matter (GM), white matter (WM) and cerebrospinal fluid (CSF) prior probability maps using linear and optimized non-linear registrations iii) used prior probability maps to perform the segmentation of a single brain tissues. Computed multimodal sheep brain templates showed to preserve and underline all brain patterns of a single T1W or T2W image, and prior probability maps allowed to improve the segmentation of brain tissues. Finally, we demonstrated that these templates and prior probability maps were able to be portable in other publicly available imaging software and could be used as standardized spaces for multi-institution neuroimaging studies or other neuroscience methods.

Mild effects of gestational stress and social reactivity on the onset of mother-young interactions and bonding in sheep

Consequences of prenatal stress on mother-young relationships are well-documented in altricial mammals but less so in precocial mammals. In this study, we investigated the effects of unpredictable aversive events on maternal behavior and mutual mother-young recognition in pregnant ewes while accounting for modulatory effects of ewe reactivity. From a population of 120 Romane-breed ewes, we selected 20 high-responsive (HR) and 20 low-responsive (LR) ewes according to pre-mating reactivity assessed in isolation tests. Over the final third of pregnancy, 10 HR ewes and 10 LR ewes were exposed daily to various aversive events such as social isolation, mixing and transport (stressed ewes), while the other 20 ewes were not exposed to aversive events (control ewes). Although the treatment induced chronic stress, physiologically confirmed by an increase in salivary cortisol following transport and sham shearing, maternal behavior of stressed ewes observed during the first 30 min postpartum and in the selectivity test 1 h 30 min later did not differ from controls. However, in a maternal motivation test performed 48 h postpartum, stressed ewes vocalized less than controls when separated from their lambs, and walked less readily past an unknown object to reach their lambs. Lambs of stressed ewes spent more time near their dam in a preference test performed 15 h after birth compared to control-ewe lambs. HR ewes spent more time grooming their lambs than LR ewes. We posit that domestication could have selected animals displaying robust expression of maternal behavior related to social reactivity and producing offspring that are better adapted to challenging situations.

Mother recognition and preference after neonatal amygdala lesions in rhesus macaques (Macaca mulatta) raised in a semi-naturalistic environment

Attachment to the caregiver, typically the biological mother, is crucial to young mammals' socio-emotional development. Although studies in nonprimate species suggest that the amygdala regulates social preference and attachment development, its role in primate filial attachment development has been little investigated and has produced mixed results. This study assessed the effects of neonatal amygdala- (Neo-A, N = 16) and sham- (Neo-C, N = 12) lesions on mother recognition and discrimination in macaques raised in species-typical social groups. Neonatal amygdalectomy did not affect social discriminative abilities and mother preference at 3 and 6 months of age, strongly suggesting that the amygdala is not involved in the cognitive processes underlying the development of filial attachment at least when the amygdala damage occurred after the third to fourth weeks of age. Nevertheless, as compared to sham-operated controls, amygdalectomized infants initiated physical contact with their mothers less frequently. The findings are discussed in relation to the known contribution of the amygdala to filial attachment in both rodents and humans.

Approaching the biology of human parental attachment: brain imaging, oxytocin and coordinated assessments of mothers and fathers

Brain networks that govern parental response to infant signals have been studied with imaging techniques over the last 15 years. The complex interaction of thoughts and behaviors required for sensitive parenting enables the formation of each individual's first social bonds and critically shapes development. This review concentrates on magnetic resonance imaging experiments which directly examine the brain systems involved in parental responses to infant cues. First, we introduce themes in the literature on parental brain circuits studied to date. Next, we present a thorough chronological review of state-of-the-art fMRI studies that probe the parental brain with a range of baby audio and visual stimuli. We also highlight the putative role of oxytocin and effects of psychopathology, as well as the most recent work on the paternal brain. Taken together, a new model emerges in which we propose that cortico-limbic networks interact to support parental brain responses to infants. These include circuitry for arousal/salience/motivation/reward, reflexive/instrumental caring, emotion response/regulation and integrative/complex cognitive processing. Maternal sensitivity and the quality of caregiving behavior are likely determined by the responsiveness of these circuits during early parent-infant experiences. The function of these circuits is modifiable by current and early-life experiences, hormonal and other factors. Severe deviation from the range of normal function in these systems is particularly associated with (maternal) mental illnesses - commonly, depression and anxiety, but also schizophrenia and bipolar disorder. Finally, we discuss the limits and extent to which brain imaging may broaden our understanding of the parental brain given our current model. Developments in the understanding of the parental brain may have profound implications for long-term outcomes in families across risk, resilience and possible interventions. This article is part of a Special Issue entitled Oxytocin and Social Behav.

Fearfulness affects quail maternal care and subsequent offspring development

Our study investigated relationships between a precocial bird’s fearfulness and maternal care, and the implication of maternal care as a vector for non-genomic transmission of fearfulness to chicks. We compared care given to chicks between two sets of female Japanese quail selected to present either high (LTI) or low fearfulness (STI). Chicks, from a broiler line, were adopted by these females following a sensitization procedure. Chicks’ fearfulness after separation from their mother was assessed by well-established procedures. LTIs took longer to present maternal responses, pecked chicks more during the first days post-hatch, presented impaired maternal vocal behaviour and were globally less active than STI females. Chicks mothered by LTIs presented more fearful reactions than did chicks mothered by STIs, supporting the hypothesis of a non-genetic maternal transmission of fearfulness. We suggest that the longer latencies required by LTIs to become maternal are a consequence of their greater fear of chicks, and that their lower general and vocal activity could be components of a heightened antipredatory strategy. We discuss the transmission of maternal fearfulness to fostered chicks, taking into account the possible implication of several well-known mechanisms underlying maternal effects.