The developmental stage of chicken embryos modulates the impact of in ovo olfactory stimulation on food preferences

Retroviral lineage analysis reveals dual contribution from ectodermal placodes and neural crest cells to avian olfactory sensory and GnRH neurons

The origin of the neurons and glia in the olfactory system of vertebrates has been controversial, with different cell types attributed to being of ectodermal placode versus neural crest lineage, depending upon the species. Here, we use replication incompetent avian (RIA) retroviruses to perform prospective cell lineage analysis of either presumptive olfactory placode or neural crest cells during early development of the chick embryo. Surprisingly, the results reveal a dual contribution from both the olfactory placode and neural crest cells to sensory neurons in the nose and Gonadotropin Releasing Hormone (GnRH) neurons migrating to the olfactory bulb. We also confirm that olfactory ensheathing glia are solely derived from the neural crest. Finally, our results show that neural crest cells and olfactory placode cells contribute to p63 positive cells, likely to be basal stem cells of the olfactory epithelium. Taken together, these finding provide evidence for previously unknown contributions of neural crest cells to some cell types in the chick olfactory system and help resolve previous discrepancies in the literature.

Impact of natural and artificial prenatal stimulations on the behavioural profile of Japanese quail

As the sensory systems of vertebrates develop prenatally, embryos perceive many environmental stimuli that can influence the ontogeny of their behaviour. Whether the nature and intensity of prenatal stimuli affect differently this ontogeny remains to be investigated. In this context, this study aimed to analyse the effects of prenatal auditory stimulations (natural stimulations "NS": predator vocalisations, or artificial stimulations "AS": metallic sounds) on the subsequent behaviour of young Japanese quail (Coturnix coturnix japonica). For that, behavioural variables recorded during ethological tests evaluating emotional and social reactivity were analysed using a principal component analysis. This analysis revealed significant differences between the behavioural profile of stimulated chicks and that of non-exposed chicks. Indeed, chicks exposed to NS expressed more intense emotional responses in fearful situations, but less neophobia in the presence of a novel environment or object, whereas chicks exposed to AS appeared more sensitive to social isolation. Our original results show that the acoustic environment of embryos can influence the way young birds subsequently interact with their social and physical environment after hatching, and face challenges in changing living conditions.

Prenatal and Early Postnatal Behavioural Programming in Laying Hens, With Possible Implications for the Development of Injurious Pecking

Injurious pecking (IP) represents a serious concern for the welfare of laying hens (Gallus gallus domesticus). The risk of IP among hens with intact beaks in cage-free housing prompts a need for solutions based on an understanding of underlying mechanisms. In this review, we explore how behavioural programming via prenatal and early postnatal environmental conditions could influence the development of IP in laying hens. The possible roles of early life adversity and mismatch between early life programming and subsequent environmental conditions are considered. We review the role of maternal stress, egg conditions, incubation settings (temperature, light, sound, odour) and chick brooding conditions on behavioural programming that could be linked to IP. Brain and behavioural development can be programmed by prenatal and postnatal environmental conditions, which if suboptimal could lead to a tendency to develop IP later in life, as we illustrate with a Jenga tower that could fall over if not built solidly. If so, steps taken to optimise the environmental conditions of previous generations and incubation conditions, reduce stress around hatching, and guide the early learning of chicks will aid in prevention of IP in commercial laying hen flocks.

Review: Management of livestock behavior to improve welfare and production

In animal production, producers face different problems inherent to production systems. Today society is increasingly concerned about more sustainable systems and animal welfare. Applied ethology can be a tool to solve some of these problems through these approaches. The purpose of this review is to show succinctly some sustainable behavioral technologies whose application favors animal welfare and productivity. The examples cover areas of behavioral problems associated with multiple births, where odor transfer can be used to substitute or add newborns to a foster mother; early weaning, where some alternatives for a gradual break may reduce the stress of separation; early experience on the development of food preferences, where behavioral problems like neophobia can be avoided; early detection of sick animals, where recognition of some specific behaviors could help early identification of diseases, even before the appearance of clinical signs; social isolation on ease of handling, where different techniques have proved their effectiveness modifying the temperament of the animals; design of facilities and management, where it is highlighted how when considering the behavior of the animals in the design and management, better results are obtained; social isolation, facilitation, and buffering, where the presence of other members of the group can modify the consumption and sexual behaviors of pen-mates, or even alleviate suffering; and human-animal interaction on productivity, where the relevance of a positive human-animal interaction is highlighted. After reviewing the scientific literature on the subject, we can conclude that several modern livestock management practices might induce stress in animals, affecting their welfare, health, and productive performance. Applied animal behavior could be a sustainable and effective option to understand and solve some of these problems, and in many cases does not even require a strong economic investment for producers.

Zebra Finch chicks recognise parental scent, and retain chemosensory knowledge of their genetic mother, even after egg cross-fostering

Mechanisms underlying parent-offspring recognition in birds have fascinated researchers for centuries. Yet, the possibility that chicks recognise parental odour at hatching has been completely overlooked, despite the fact that olfaction is one of the first sensory modalities to develop, and social chemosignals occur in avian taxa. Here we show that Zebra Finch chicks (Taeniopygia guttata) are capable of identifying parental odours at hatching. In our first experiment, chicks begged significantly longer in response to the odour of their genetic mother or father compared to the odour of a non-relative of the same sex and reproductive status. In a second experiment, we cross-fostered eggs and tested the response of hatchlings to the scent of genetic vs. foster parents. Chicks from cross-fostered eggs responded significantly more to the odour of their genetic mother than their foster mother, but exhibited no difference in response to genetic vs. foster fathers. This is the first evidence that embryonic altricial birds are capable of acquiring chemosensory knowledge of their parents during early development, and retain chemical familiarity with their genetic mother despite egg cross-fostering. Furthermore our data reveals that kin recognition in birds can develop without any association with a genetic parent at hatching.

Embryonic exposure of chicken chicks (Gallus gallus domesticus) leads to heightened sensitivities towards the exposed scent

In chickens, food consumption can be altered by exposing the chicks to scents as embryos. We exposed eggs to an orange-scented food additive in the final days of incubation. Following hatching, we tested these exposed chicks’ ability to detect this scent at a variety of concentrations. We found that orange-exposed chicks responded to an orange-scented solution at lower concentrations than control chicks. This sensitization may allow chicks to be more effective at locating acceptable food items but requires further testing to determine its significance. Orange-exposed and control chicks were also tested with the scent of raspberry. Orange-exposed chicks responded to the raspberry presentation significantly more than the control chicks did, suggesting that the embryonic exposure to orange may have influenced how the chicks responded towards another fruity smell. This result suggests that chicks may be learning general characteristics of exposed scents while in the egg, though this needs further research.

Chronic odorant exposure upregulates acquisition of functional properties in cultured embryonic chick olfactory sensory neurons

Neuronal development and differentiation is modulated by activity-dependent mechanisms that stimulate endogenous neurogenesis and differentiation to promote adaptive survival of the organism. Studies on bird odor imprinting have shown how sensory stimuli or environmental influences can affect neonatal behavior, presumably by remodeling the developing nervous system. It is unclear whether these changes originate from the sensory neurons themselves or from the brain. Thus, we attempted to address this by using an in vitro system to separate the peripheral neurons from their central connections. Olfactory neurons from embryonic day 17 Gallus domesticus chicks were isolated, cultured, and exposed to 100 µM amyl acetate or phenethyl alcohol in 12-hr bouts, alternated with periods of no-odor exposure. On days 4 and 5 in vitro, cells were immunostained for olfactory marker protein, neuron-specific tubulin, and olfactory GTP-binding protein, and tested for odorant sensitivity using calcium imaging. While odorant exposure did not result in a significant increase in the overall number of neurons, it promoted neuron differentiation: a larger proportion of odorant-exposed cells expressed olfactory marker protein and the olfactory GTP-binding protein. When cell responsiveness was tested using calcium imaging, a greater proportion of odorant-exposed cells responded to stimulation with 100 µM amyl acetate or phenethyl alcohol. Thus, odorant exposure during development modulated the developmental trajectories of individual neurons, resulting in changes in protein expression associated with odorant signaling. This suggests that the neuronal changes in the periphery have an important contribution to the overall long-term functional changes associated with odor imprinting. © 2016 Wiley Periodicals, Inc.

Yolk hormones influence in ovo chemosensory learning, growth, and feeding behavior in domestic chicks

In this study, we assessed whether prenatal exposure to elevated yolk steroid hormones can influence in ovo chemosensory learning and the behavior of domestic chicks. We simulated a maternal environmental challenge by experimentally enhancing yolk progesterone, testosterone, and estradiol concentrations in hen eggs prior to incubation. The embryos from these hormones-treated eggs (HO) as well as sham embryos (O) that had received the vehicle-only were exposed to the odor of fish oil (menhaden) between embryonic Days 11 and 20. An additional group of control embryos (C) was not exposed to the odor. All chicks were tested following hatching for their feeding preferences between foods that were or were not odorized with the menhaden odor. In the 3-min choice tests, the behavior of O chicks differed significantly according to the type of food whereas C and HO chicks showed no preference between odorized and non-odorized food. Our result suggests weaker response in HO chicks. In addition, HO chicks showed impaired growth and reduced intake of an unfamiliar food on the 24-h time scale compared to controls. Our data suggest that embryonic exposure to increased yolk hormone levels can alter growth, chemosensory learning, and the development of feeding behaviors.

The perfume of reproduction in birds: chemosignaling in avian social life

This article is part of a Special Issue "Chemosignals and Reproduction". Chemical cues were probably the first cues ever used to communicate and are still ubiquitous among living organisms. Birds have long been considered an exception: it was believed that birds were anosmic and relied on their acute visual and acoustic capabilities. Birds are however excellent smellers and use odors in various contexts including food searching, orientation, and also breeding. Successful reproduction in most vertebrates involves the exchange of complex social signals between partners. The first evidence for a role of olfaction in reproductive contexts in birds only dates back to the seventies, when ducks were shown to require a functional sense of smell to express normal sexual behaviors. Nowadays, even if the interest for olfaction in birds has largely increased, the role that bodily odors play in reproduction still remains largely understudied. The few available studies suggest that olfaction is involved in many reproductive stages. Odors have been shown to influence the choice and synchronization of partners, the choice of nest-building material or the care for the eggs and offspring. How this chemical information is translated at the physiological level mostly remains to be described, although available evidence suggests that, as in mammals, key reproductive brain areas like the medial preoptic nucleus are activated by relevant olfactory signals. Olfaction in birds receives increasing attention and novel findings are continuously published, but many exciting discoveries are still ahead of us, and could make birds one of the animal classes with the largest panel of developed senses ever described.

Choice alters Drosophila oviposition site preference on menthol

Food choice and preference relies on multiple sensory systems that are under the control of genes and sensory experience. Exposure to specific nutrients and nutrient-related molecules can change food preference in vertebrates and invertebrates. For example, larval exposure of several holometabolous insects to menthol can change their adult response to this molecule. However, studies involving Drosophila melanogaster exposure to menthol produced controversial results due maybe to methodological differences. Here, we compared the oviposition-site preference of wild-type D. melanogaster lines freely or forcibly exposed to menthol-rich food. After 12 generations, oviposition-site preference diverged between the two lines. Counterintuitively, menthol 'forced' lines showed a persistent aversion to menthol whereas 'free choice' lines exhibited a decreased aversion to menthol-rich food. This effect was specific to menthol since the 'free choice' lines showed unaltered responses to caffeine and sucrose. This suggests that the genetic factors underlying Drosophila oviposition site preference are more rapidly influenced when flies have a choice between alternative sources compared to flies permanently exposed to the same aversive substance.

The Colorado LEAP study: rationale and design of a study to assess the short term longitudinal effectiveness of a preschool nutrition and physical activity program

BACKGROUND

The preschool years are a critical window for obesity prevention efforts; representing a time when children establish healthy eating habits and physical activity patterns. Understanding the context in which these behaviors develop is critical to formulating a model to address childhood obesity. The Colorado LEAP Study, an intervention study designed to prevent early childhood obesity, utilizes a social ecological approach to explore individual, family and environmental factors and their relationship to child weight status over a 3 year timeframe.

METHODS

The study is located in 5 rural Colorado preschool centers and elementary schools (2 treatment and 3 control). Treatment sites receive The Food Friends nutrition (12 weeks) and physical activity (18 weeks) interventions during preschool. Observational measures assess 3 layers of the social ecological model including individual, family and organizational inputs. Children's food preferences, food intake, gross motor skills, physical activity (pedometers/accelerometers), cognitive, physical and social self-competence and height/weight are collected. Parents provide information on feeding and activity practices, child's diet, oral sensory characteristics, food neophobia, home food and activity environment, height/weight and physical activity (pedometers). School personnel complete a school environment and policy assessment. Measurements are conducted with 3 cohorts at 4 time points - baseline, post-intervention, 1- and 2-year follow-up.

DISCUSSION

The design of this study allows for longitudinal exploration of relationships among eating habits, physical activity patterns, and weight status within and across spheres of the social ecological model. These methods advance traditional study designs by allowing not only for interaction among spheres but predictively across time. Further, the recruitment strategy includes both boys and girls from ethnic minority populations in rural areas and will provide insights into obesity prevention effects on these at risk populations.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01937481.

Maternal diet influences offspring feeding behavior and fearfulness in the precocial chicken

Background

In chicken, oils in the maternal diet confer a specific scent to the yolk. Embryos are known to perceive and memorize chemosensory signals of the surrounding environment; however, the potential impact of the maternal diet has not previously been investigated. In the present study, we hypothesized that chicken embryos memorize the chemical signals of the maternal diet and that this perceptual learning may orient subsequent feeding behavior of the hatchlings.

Methodology/Principal Findings

Laying hens were fed standard food enriched with 2% menhaden oil (MH group) or 2% soybean oil (controls). The scent of menhaden was significantly more detected in MH egg yolks than in control yolks by a human panel. We analyzed the development and behavior of offspring towards different types of food, bearing or not bearing the menhaden scent. When chicks were exposed to a 3-min choice test between the familiar food bearing the menhaden scent and the familiar food without menhaden, no effect of treatment was observed. In a 3-min choice test with unfamiliar food (mashed cereals) MH chicks showed a clear positive orientation toward the unfamiliar food bearing the menhaden scent. By contrast, control chicks showed a preference for the non-odorized unfamiliar food. MH chicks expressed higher emotional reactivity level than control chicks as expressed by food neophobia and longer immobility in a restraint test.

Conclusion/Significance

Chicks exposed in ovo to menhaden oil via the maternal diet preferentially oriented their feeding behavior towards food containing menhaden oil, but only when the food was unfamiliar. We propose that oil in the maternal diet engenders maternal effects and contributes to the development of behavioral phenotype in the offspring. In ovo chemosensory learning may have evolved to prepare precocial offspring for their environment. This suggests a common principle of embryonic chemosensory learning across vertebrate taxa.