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.

The Effects of Postmortem Time on Muscle Trout Biochemical Composition and Structure.

Fish industry operators have to process fish that arrive at various postmortem times. Postmortem time constrains processing and impacts product quality, safety, and economic value. The objective identification of biomarkers is desirable to predict the postmortem day of aging and this requires a comprehensive longitudinal characterisation of postmortem aging. We analysed the postmortem aging process in trout over a 15-day window. Quantitative physicochemical measurements (pH, colour, texture, aw, proteolysis, and myofibrillar protein solubility) performed on the same fish over time revealed the levels of protein denaturation, solubility, and pH, among other parameters, change very little when assessed by conventional chemical methods. Histological analyses were performed on thin sections and revealed fibre ruptures after 7 days of storage on ice. Ultrastructures were observed by transmission electronic microscopy (TEM) and revealed that sarcomere disorganisation occurred more often after 7 days of storage. Label-free FTIR micro-spectroscopy combined with a SVM model accurately predicted the postmortem time. Spectra-based PC-DA models also enable the identification of biomarkers corresponding to Day 7 and Day 15 postmortem. This study provides insights on postmortem aging and raises prospects for the rapid assessment of trout's freshness status from label-free imaging.

Investigation by Synchrotron Radiation Circular Dichroism of the Secondary Structure Evolution of Pepsin under Oxidative Environment.

Food processing affects the structure and chemical state of proteins. In particular, protein oxidation occurs and may impair protein properties. These chemical reactions initiated during processing can develop during digestion. Indeed, the physicochemical conditions of the stomach (oxygen pressure, low pH) favor oxidation. In that respect, digestive proteases may be affected as well. Yet, very little is known about the link between endogenous oxidation of digestive enzymes, their potential denaturation, and, therefore, food protein digestibility. Thus, the objective of this study is to understand how oxidative chemical processes will impact the pepsin secondary structure and its hydrolytic activity. The folding and unfolding kinetics of pepsin under oxidative conditions was determined using Synchrotron Radiation Circular Dichroism. SRCD gave us the possibility to monitor the rapid kinetics of protein folding and unfolding in real-time, giving highly resolved spectral data. The proteolytic activity of control and oxidized pepsin was investigated by MALDI-TOF mass spectrometry on a meat protein model, the creatine kinase. MALDI-TOF MS allowed a rapid evaluation of the proteolytic activity through peptide fingerprint. This study opens up new perspectives by shifting the digestion paradigm taking into account the gastric digestive enzyme and its substrate.

Human-lamb bonding: oxytocin, cortisol and behavioural responses of lambs to human contacts and social separation.

Friendly interactions between humans and animals such as gentling or petting have been shown to have positive behavioural and physiological consequences in many species. In primates, rodents and dogs, oxytocin has been associated with tactile contact and anti-stress effects that may influence bonding and responses to stress situations. However the activation of the oxytocinergic system in other human-animal interactions such as with herbivores, had not yet been studied. Sixteen female lambs were reared by artificial feeding reinforced with 3× 30 s daily stroking sessions. At 6 weeks of age, the test consisted in measuring first plasma oxytocin and cortisol responses in lambs during a first 6-min phase in the home pen where the familiar caregiver gently stroked the lamb, and then physiological and behavioural responses in a test pen during a 20-min - phase of social isolation followed by a 20-min - phase of reunion with its familiar caregiver. The lambs expressed behavioural agitation during the whole period of isolation. A strong affiliative response towards the human and a sustained reduction of the agitation behaviour were observed during reunion. Lambs' behaviours when isolated and when in contact with the human were correlated suggesting a response to social separation from the familiar caregiver more than to social isolation from congeners. No significant changes in cortisol levels were observed during the test. Oxytocin levels did not vary during human contact, but increased when the familiar caregiver left the lamb alone in the test pen. In conclusion, lambs displayed affiliative responses towards their caregiver, and the lack of cortisol response during isolation while oxytocin was released suggest an anti-stress effect of oxytocin.