Abstract: Salivary cortisol has been increasingly used as a measure of stress response in studies of welfare, reaction to stress and human–animal interactions in dogs and other species. While it can be a very useful measure, there are a number of saliva collection issues made evident through studies in the human and animal fields which have not been investigated in the canine species. Collection materials and the volume of saliva that is collected; the use of salivary stimulants; and the effect of food contamination can all dramatically impact cortisol measurement, leading to spurious results. In order to further examine the limitations of the collection method and the effects of collection material and salivary stimulant on salivary cortisol levels, a series of clinical, in vitro and in vivo studies were performed. It was found that there is a large amount of inter- and intra-individual variation in salivary cortisol measurement. Beef flavoring of collection materials leads to unpredictable variability in salivary cortisol concentration. Using salivary stimulants such as citric acid also has the potential to affect cortisol concentration measurement in saliva. Hydrocellulose appears to be a useful collection material for salivary cortisol determination. Recommendations for collection materials and use of salivary stimulants are presented.

Abstract: Even though the term “stress” is widely used, a precise definition is notoriously difficult. Notwithstanding this difficulty, stress continues to be an important concept in biology because it attempts to describe how animals cope with environmental change under emergency conditions. Without a precise definition, however, it becomes nearly impossible to make testable a priori predictions about how physiological and hormonal systems will respond to emergency conditions and what the ultimate impact on the animal will be. The reactive scope model is a recent attempt to formulate testable predictions. This model provides a physiological basis to explain why corticosterone negative feedback, but not baseline corticosterone concentrations, corticosterone responses to acute stress, or the interrenal capacity to secrete corticosterone, is correlated with survival during famine conditions in Galápagos marine iguanas. Reactive scope thus provides a foundation for interpreting and predicting physiological stress responses.

Abstract: In group-living animals relative rank positions are often associated with differences in glucocorticoid output. During phases of social stability, when dominance positions are clear and unchallenged, subordinates often face higher costs in terms of social stress than dominant individuals. In this study we test this prediction and examine additional potential correlates of stress, such as reproductive season, age and amount of aggression received in wild, seasonally breeding Assamese macaques (Macaca assamensis). During a mating and a non-mating season we collected 394 h of focal observational data and 440 fecal samples of six adult and six large subadult males living in a multimale-multifemale group in their natural habitat in northeastern Thailand. The mating season was characterized by a general increase in aggressive behavior and glucocorticoid excretion across all males compared to the non-mating season. Among adult males, mating season glucocorticoid levels were significantly negatively related with dominance rank and positively with the amount of aggression received. Both relationships were non-significant among large subadult males. Thus, our results suggest that in adult Assamese macaques a high dominance position is not associated with high costs. Low costs of dominance might be induced by strong social bonds among top-ranking males, which exchange frequent affiliative interactions and serve as allies in coalitionary aggression against potentially rank-challenging subordinate males.

Abstract: The left and right sides of the brain are specialised to process information in different ways and to control different categories of behaviour. Research on a range of species has shown that the left hemisphere controls well-established patterns of behaviour performed in non-stressful situations, whereas the right hemisphere responds to unexpected stimuli and controls escape and other emergency responses. The known functions of each hemisphere are summarised in this paper. Then it is hypothesised that stressed animals rely on predominant use of the right hemisphere, and that a bias to use the right or left hemisphere, respectively, may explain the behavioural differences between animals with a negative cognitive bias and those with a positive cognitive bias. In some species of primates it has been shown that the preferred limb used to pick up food when the animal is in a relaxed state reflects the dominant hemisphere and may be an accessible measure indicating susceptibility to stress and tendency towards positive versus negative cognitive bias. Hence, limb preference might be a useful measure of such tendencies in domesticated species. Some difficulties in determining a relevant measure of limb preference in non-primate species are mentioned, followed by the suggestion that eye preferences for viewing certain stimuli may be a useful measure in species with laterally placed eyes. Finally, effects of experience on the development of hemispheric dominance are discussed, leading to a suggestion that the welfare of domestic animals may be enhanced by ensuring development of left hemisphere dominance (e.g. by exposing chick embryos to light) and by shifting right to left hemisphere dominance in animals with negative cognitive bias.

Abstract: For free-living or feral horses weaning takes place naturally at around 8-9 months [Gill, E.L., 1988. Factors affecting body condition of New Forest Ponies. Ph.D. Thesis. Department of Biology, University of Southampton]. Some mares will continue to suckle their foal until shortly before the arrival of their next foal, gestation being approximately 342 days depending upon the breed of the horse [Ropiha, R.T., Mathews, G., Butterfield, R.M., 1969. The duration of pregnancy in Thoroughbred mares. Vet. Rec. 84, 552-555]. Under domestic conditions, weaning tends to take place earlier, typically between 4 and 6 months of age. The weaning process has been identified as associated with potential psychological, physical and nutritional stressors that are of welfare concern. Following a review of the literature it is evident that there is a need for detailed research into what should constitute best practice with respect to foal and mare welfare. In addition, there is a need to understand the potential long-term impact of weaning on, for example, trainability and later maternal behaviour, and whether the stresses associated with early weaning have detrimental effects on the performance horse. There is also a lack of clear information concerning the most frequently observed weaning practices and the reasons why certain weaning methods are chosen. Some variables should be closely managed during weaning in order to minimise stress responses. These include: early creep feeding to familiarise the young animal with the food it will be exposed to during weaning, feeding a high fibre diet and keeping the animal in extensive conditions using a gradual approach to weaning. However, we conclude that there may not be one best method for weaning, since the chosen method must take into account a number of factors including: available resources, the housing environment, the individual foal's stage of development, the strength of the mare-foal attachment, the foal's ability to cope with changes in social conditions and the ability of the horse owner to implement the chosen method. We do however suggest that the fewest stress responses appear to occur where foals are weaned gradually and allowed to have social contact either with other foals or with older horses.