Matthijs B.H. Schilder

Behavioural, saliva cortisol and heart rate responses to different types of stimuli in dogs

Abstract Stress parameters that can be measured noninvasively may help to identify poor welfare in dogs that live in private homes and institutions. Behavioural parameters are potentially useful to identify stress, but require further investigation to establish which behaviours are appropriate. In the present study, behaviours were recorded and analysed for signs of acute stress in dogs. Simultaneously, saliva cortisol and heart rate were measured to support the interpretation of the behavioural data with regard to stress. Ten dogs of either sex, different ages and various breeds were each subjected to six different stimuli: sound blasts, short electric shocks, a falling bag, an opening umbrella and two forms of restraint. Each type of stimulus had been selected for its assumed aversive properties and was administered intermittently for 1 min. The stimuli that could not be anticipated by the dogs, sound blasts, shocks and a falling bag, tended to induce saliva cortisol responses and a very low posture. The remainder of the stimuli, which were administered by the experimenter visibly to the dog, did not change the cortisol levels but did induce restlessness, a moderate lowering of the posture, body shaking, oral behaviours, and to a lesser extent, yawning and open mouth. Pronounced increases in the heart rate were nonspecifically induced by each type of stimulus. Heart rate levels normalized within 8 min after stressor administration had stopped. Saliva cortisol levels decreased to normal within the hour. Correlations between behavioural and physiological stress parameters were not significant. From the present results, we conclude that in dogs a very low posture may indicate intense acute stress since dogs show a very low posture concomitant with saliva cortisol responses. Dogs may typically show increased restlessness, oral behaviours, yawning, open mouth and a moderate lowering of the posture when they experienced moderate stress in a social setting. The nonspecific character of canine heart rate responses complicates its interpretation with regard to acute stress.

Heart rate and heart rate variability during a novel object test and a handling test in young horses.

Forty-one Dutch Warmblood immature horses were used in a study to quantify temperamental traits on the basis of heart rate (HR) and heart rate variability (HRV) measures. Half of the horses received additional training from the age of 5 months onwards; the other half did not. Horses were tested at 9, 10, 21 and 22 months of age in a novel object and a handling test. During the tests, mean HR and two heart variability indices, e.g. standard deviation of beat-to-beat intervals (SDRR) and root mean square of successive beat-to-beat differences (rMSSD), were calculated and expressed as response values to baseline measures. In both tests, horses showed at all ages a significant increase in mean HR and decrease in HRV measures, which suggests a marked shift of the balance of the autonomic nervous system towards a sympathetic dominance. In the novel object test, this shift was more pronounced in horses that had not been trained. Furthermore, statistical analysis showed that the increase in mean HR could not be entirely explained by the physical activity. The additional increase in HR, the nonmotor HR, was more pronounced in the untrained horses compared to the trained. Hence, it is suggested that this nonmotor HR might be due to the level of emotionality. HR variables showed consistency between years, as well as within the second year. These tests bring about a HR response in horses, part of which may indicate a higher level of emotionality; and horses show individual consistency of these HR variables over ages. Therefore, it is concluded that mean HR and HRV measures used with these tests quantify certain aspects of a horses temperament.

Manifestations of chronic and acute stress in dogs

Abstract Poor housing conditions, harsh training sessions and uncontrollable or unpredictable social environments are examples of the situations that may lead to reduced welfare status in dogs. Individuals that suffer from poor welfare presumably experience stress and may consequently exhibit stress responses. In order to evaluate stress responses as potential indicators of poor welfare in dogs, we review studies dealing with dogs subjected to stressors. The reported stress responses are categorized as being behavioural, physiological or immunological, and demonstrate the various ways stress is manifested in the dog. Stressors such as noise, immobilization, training, novelty, transport or restricted housing conditions have been reported to elicit responses in behavioural, cardiovascular, endocrine, renal, gastro-intestinal, and haematological parameters. These and other parameters that change during stress may thus be indicative of poor welfare. However, several sources of misinterpretation have to be considered before stress responses may be used as valid indicators of welfare. Although analogous to the human situation, especially chronic stress may impair welfare, most studies deal with acute stress and do not address chronic stress and related phenomena. Adaptation may counteract the initial stress response and render parameters of acute stress useless for assessing chronic stress. Adaptations to stress are thus in themselves indicative of reduced welfare. Such adaptations may be discovered by challenging a stress responsive system. Additional studies are recommended to investigate acute stress parameters as possible indicators of chronic stress. Differences in stressor properties and in individual characteristics of dogs introduce variability in stress responses. Such variability will complicate a valid interpretation of stress responses with regard to welfare. Obtaining and applying fundamental knowledge of stress responses in dogs and measuring more than one stress parameter are proposed to minimize the risk of misinterpreting measurements of stress.

Quantifying aspects of young horses’ temperament: consistency of behavioural variables

Performance of horses, whether in sports or in leisure, depends on both physical abilities as well as temperament. The aim of the present work was to measure individual variation and consistency of behavioural variables, related to temperament, in young horses of the same breed and age, and reared under controlled housing conditions and management. A total of 41 Dutch Warmblood horses were tested at 9, 10, 21 and 22 months of age in two behavioural tests, i.e. the novel object test and the handling test. In the novel object test horses were confronted with an open umbrella that was lowered from the ceiling. In the handling test horses were led by a human to cross a bridge. Per test, behavioural variables in the following behavioural classes were observed: locomotor activity, latency times, postural expressions and vocalisations. Within years, all behavioural variables in the handling test, and all but two in the novel object test were positively correlated (0.36<Rs<0.81, P<0.05). For both tests, at 9, 10, 21 and 22 months of age, a principal component analysis (PCA) was carried out to examine whether there were indications for underlying components of these individual behavioural variables that could possibly serve as measures for temperamental traits. The first component in the novel object test could be regarded as ‘flightiness’ and the second as ‘sensitiveness’. In the handling test, the first component was suggested to relate to ‘patience’, the second component to ‘willingness to perform’. The temperamental trait ‘flightiness’ (novel object test) as well as the temperamental trait ‘patience’ (handling test) were positively correlated within both years (0.36<Rs<0.65, P<0.05). For the traits ‘sensitiveness’ (novel object test) and ‘willingness to perform’ (handling test) a positive correlation was only found within the first year (0.44<Rs<0.57, P<0.01). A few individual behavioural variables showed consistency over years. Additionally, just one out of four temperamental traits, namely ‘flightiness’, proved to be consistent over years (Rs=0.49, P<0.01). The temperamental trait ‘patience’ showed a trend between years (Rs=0.31, 0.05<P<0.1). It is concluded that the behavioural tests employed in the present study can be used to reliably identify individual behavioural variables and temperamental traits in young horses. Long-term consistency, i.e. between subsequent years, could not be demonstrated convincingly. Nevertheless, future work may indicate that employing the same approach and considering an even longer time period or different phases of the horse’s life, long-term consistency does exist.

The Use of Saliva Cortisol, Urinary Cortisol, and Catecholamine Measurements for a Noninvasive Assessment of Stress Responses in Dogs

A problem in assessing animal welfare is that collecting data in itself may be stressful to the animals. Therefore, noninvasive methods for collecting data have to be devised and tested. A first step in investigating saliva cortisol, urinary cortisol, and urinary catecholamine as noninvasive indicators of canine well-being is the validation of these hormonal measures as alternatives for those in plasma. Using a model of insulin (0.2 U/kg)-induced hypoglycemia, we report on stress-induced responses in saliva cortisol, urinary cortisol, and urinary catacholamines relative to cortisol and catecholamine responses in plasma. Hypoglycemia in six dogs induced significant (P < 0.05) increases in plasma cortisol and adrenaline but not noradrenaline. Saliva cortisol responses expressed as net area under the response curve correlated significantly with plasma cortisol responses (r > 0.92). Saliva cortisol levels measured 7 to 12% of plasma cortisol concentrations. Cortisol/creatinine rations in urine were significantly higher when voided after insulin administeration, compared to when voided after saline treatment. Insulin-induced increments in cortisol/ creatinine ratios were nonsignificant when urine samples were assayed after dichloromethane extraction. Although urinary adrenaline/creatinine (A/C) ratios were significantly correlated with maximum plasma adrenaline values after insulin administration, A/C ratios did not differ significantly between insulin and saline treatment. The present experiment provides strong support for using saliva sampling and urine collection as noninvasive methods to establish stress-induced cortisol responses. For measuring acute plasma adrenaline responses, measuring A/C ratios may not be a valid alternative.

Chronic stress in dogs subjected to social and spatial restriction. II. Hormonal and immunological responses.

Two groups of beagles, accustomed to spacious group housing, were subjected to social and spatial restriction and studied for manifestations of chronic stress with a time interval of 7 weeks between the groups. The change from outside group housing (the control period) to individual housing in small indoor kennels resulted in sustained decreases in urinary adrenaline/creatinine and noradrenaline/creatinine ratios for the total group. Urinary dopamine/creatinine and noradrenaline/adrenaline ratios were statistically unaffected. Socially and spatially restricted dogs that had experienced pleasant weather during the control period showed (a) increased salivary and urinary cortisol concentrations, (b) a diminished responsiveness of the pituitary-adrenal axis to a sudden sound blast or exogenous CRH, (c) intact plasma ACTH and cortisol suppressions after dexamethasone administration, and (d) increased concanavalin A induced lymphocyte proliferations. When social and spatial restriction was preceded by a control period during which the weather was bad, these physiological responses were either augmented (lymphocyte proliferation), or offset (salivary and urinary cortisol), or directed oppositely (CRH-induced ACTH and cortisol responses). Together with the previously presented behavioral observations, these data suggest that bad weather conditions during spacious outdoor group housing induced early stress that attenuated the negative appraisal of the subsequent period of social and spatial restriction. In comparison to male dogs, bitches showed increased HPA responses to a sound blast or exogenous CRH. Their increased attenuations of the ACTH and cortisol responses to CRH after 5 weeks of restricted housing indicates that bitches are not only more susceptible to acute stress, but also to chronic housing stress. It is concluded that the quality of circumstances preceding a period of affected well-being determines the magnitude and even the direction of the behavioral and physiological stress responses. Basal salivary and urinary cortisol measurements are useful for the assessment of chronic stress, and of poor welfare in dogs. The use of urinary catecholamine, peripheral leucocyte, and lymphocyte proliferation measures requires further investigation.

An analysis of dominance, its behavioural parameters and possible determinants in a herd of Icelandic horses in captivity

The applicability of the concept of dominance was investigated in a captive herd of 26 Icelandic horses and 5 ponics of different breeds. Eight out of 20 behaviours possibly related to dominance occurred frequently enough to be investigated in detail. For these eight agonistic behaviours the coverage, the unidirectionality in the exchange, and the degree of transitivity (Landaus lincrarity index) were calculated. Four offensive behaviours, together with avoidance, were suitable for further analysis with regard to dominance. The patterns of asymmetries with which these behaviours were exchanged were sufficiently similar as to justify the application of the dominance concept and to construct a (nearly) linear dominance hierarchy. The rank order of the castrated stallions was completely linear, the hierarchy of the mares was almost completely linear. The results suggest that offensive and defensive aggressive behaviours should be treated separately and that the concept of dominance is applicable. However, ritualized formal dominance signals between adult horses appear to be (almost) absent. The rank positions of the individuals were correlated with age and residency in the herd but not with height. Middle ranking horses tended to be more frequently in the close vicinity of an other horse than high ranking or low ranking horses. Over and above this correlation at the individual level, it was found that pairs of horses close in rank to each other were more often also spatially close to each other. Being in oestrus did not influence the dominance relationships between mares. For castrated stallions the rank positions were correlated with the age at which they were castrated. This suggests that in male horses experience prior to neutering influences the behaviour afterwards.

Learning performances in young horses using two different learning tests

To achieve optimal performance in equine sports as well as in leisure not only the physical abilities of the horse should be considered, but also the horses personality. Besides temperamental aspects, like emotionality, or the horses reactivity towards humans in handling situations, the learning ability of the horse is another relevant personality trait. To study whether differences in learning performance are consistent over time and whether individual learning performance differs between learning tests or is affected by emotionality, 39 young horses (Dutch Warmblood) were tested repeatedly in two learning tests. An aversive stimulus (AS) was used in one learning test (the avoidance learning test) and a reward was used in the other learning test (the reward learning test). During both learning tests behaviour as well as heart rate were measured. Each test was executed four times, twice when horses were 1 year of age, and twice when they were 2 years of age. Half of the horses received additional physical training from 6 months onwards. In both tests horses could be classified as either performers, i.e. completing the daily session, or as non-performers, i.e. returning to the home environment without having completed the daily session. There were some indications that emotionality might have caused non-performing behaviour, but these indications are not convincing enough to exclude other causes. Furthermore, there seem to be no simple relationships between measures of heart rate, behavioural responses putatively related to emotionality and learning performance. Horses revealed consistent individual learning performances within years in both tests, and in the avoidance learning test also between years. There was no significant correlation between learning performances in the avoidance learning test and the learning performances in the reward learning test. It is concluded that individual learning abilities are consistent over a short time interval for an avoidance learning test and a reward learning test and over a longer time for the avoidance learning test. Furthermore, results indicate that some horses perform better when they have to learn to avoid an aversive stimulus while others perform better when they are rewarded after a correct response. It is suggested that these differences may be relevant to design optimal individual training programmes and methods.

The association between performance in show-jumping and personality traits earlier in life

For a horse to succeed in a show-jumping career, the individual has to possess both excellent physical abilities as well as a suitable personality to perform under challenging conditions. Forty-one Dutch Warmblood horses were used to develop personality tests and correlations between test variables and early training performances in jumping were studied. In behavioural tests, during the first 2 years of the horses’ lives, personality aspects like emotionality, reactivity to human and learning abilities were quantified. At the age of 3, horses were broken and received early training in show-jumping. The inter-relationship between several performance variables measured during this early training phase were studied using principal component analysis (PCA). Variables measured in the different personality tests (novel-object test, handling test, avoidance-learning test and a reward-learning test) showed no correlations, suggesting that these tests all triggered different aspects of a horse’s personality. This study indicates that it is possible to predict a substantial part of the show-jumping performance of an individual horse later in life by personality traits earlier in life.

Behavior genetics of canine aggression: Behavioral phenotyping of golden retrievers by means of an aggression test

Molecular genetic analysis of complex traits such as aggression strongly depends on careful phenotyping of individuals. When studying canine aggression, the information provided by the owners of the dogs is often not detailed and reliable enough for this purpose. Therefore we subjected 83 golden retrievers, both aggressive and nonaggressive individuals, to a behavioral test. These tests were analyzed with help of an ethogram, resulting in a behavioral profile for each of the dogs. In this article three methods are described of converting these profiles into a measure of behavioral phenotype. The usefulness of the methods is evaluated by comparing the test results with information provided by owners. Moreover, the hypothesis underlying all these methods, that a lowered threshold for aggressive behavior in general is present in the dogs, is also evaluated. Future research will need to reveal whether the methods meet the high standards that are necessary for studying complex traits.