Non-invasive welfare evaluations in horses : the usefulness of laterality

Animal welfare is becoming increasingly important, especially for animal owners. In particular, prey animals such as horses generally suffer in silence. To improve the evaluation of animal welfare in practice and to simplify it in scientific research, new welfare indicators are needed that are easier to assess, less time consuming, and repeatable. Therefore, this thesis aimed to investigate laterality as a welfare indicator that could meet these requirements. Domestic horses were used as model organisms as they display sensory and motor laterality on individual and/or population level; their sensory organs are placed laterally, non-invasive stress hormone analysis is already well-established, as a highly social animal that evolved on open ranges it is prone to suffering from inappropriate human management regimes, and it displays various stress responses. In STUDY it could be demonstrated that a shift to an enhanced preference for the right brain hemisphere was in line with increased stress hormone concentrations in faeces. Sensory laterality and motor laterality measured while grazing, shifted to the left when natural needs were restricted by a change from group to individual housing. Sensory laterality changed immediately after the change of housing conditions, whereas the motor laterality changed with a time delay of one week. STUDY 2 demonstrated that motor laterality measured as initial forelimb use correlated with the cognitive bias (welfare indicator). Right-sided horses were faster to approach an ambiguous stimulus and therefore displayed a positive cognitive bias. But neither motor laterality, measured through grazing stance, nor sensory laterality were related to cognitive bias. STUDY 3 demonstrated that a preference for left side sensory organ use is not only evident in negative contexts but also in positive contexts, because the horses also preferred their left side during affiliative interactions that are assumed to induce positive emotions. This study demonstrated that not only the direction of shift in laterality, but also the context of the shift, should be recorded to reliably identify poor or good welfare. Therefore, it is recommended that additional stress parameters be applied to reliably evaluate animal welfare. STUDY 4 investigated whether the sampling and analysis of faecal stress hormones and immunoglobulin A could be simplified by applying a novel conservation method. Often it is not possible to immediately freeze the faecal samples and/or the transportation to the lab is lengthy. The study demonstrated that faecal samples can be dried a closed system such as an air-tight tube containing silica gel. The samples were dried within 24 hours, as fast as in controlled air-drying conditions at room temperature. The new and simpler drying method prevented the stress hormones (glucocorticoid metabolites) from enzymatic degradation and conserved them, demonstrated by the fact that the detectable concentration remained unchanged. In contrast, immunoglobulin A showed a reduction in the detectable concentration. Therefore, if possible, the conservation of faecal samples should be avoided when immunoglobulin A is to be analysed, although it would be possible to apply an extrapolation to attain fairly reliable results. This new drying method will simplify research on wild horses into the type of stressors they are confronted with, the impact of natural stressors, and effect of stressors on, for example, their laterality in comparison with domestic horses. STUDY 5 investigated whether the strength of laterality provides insight into basal physiological and immunological status, stress response, stress reactivity, or cognitive bias. Only a correlation between age and the strength of laterality was found, with strength of laterality increasing with age. However, age could explain only 30 per cent of the inter-individual variation in strength of laterality. The results demonstrated that the strength of laterality is not a reliable indicator of animal welfare. The direction of laterality may be of greater importance. Altogether, it was demonstrated that laterality is a promising, reliable, repeatable, and objective indictor of animal welfare, which is quick and easy to asses, and inexpensive. Like other well-established welfare and stress indicators, laterality has its limitations. Therefore, it is recommended that other welfare indicator should be simultaneously assessed and changes in laterality recorded, as different traits and personalities result in a high inter-individual variation in base laterality indices. Possible influences and correlations between emotional processing and cerebral lateralization are discussed. Nonetheless, further research is needed to establish a more reliable measurement of motor laterality, and to better understand the relationship between emotional processing and lateralization, as well as possible influencing factors.Das Tierwohl rückt für Tierbesitzer immer mehr in den Mittelpunkt. Insbesondere Fluchttiere wie Pferde können mit lediglich subtilen äußeren Anzeichen in Stille leiden. Daher sind Tierwohlindikatoren notwendig, die einfach in ihrer Bestimmung sind, wenig Zeit benötigen und wiederholbar sind, um die Bestimmung des Tierwohls in der Praxis zu verbessern und in der Wissenschaft zu vereinfachen. Deshalb war es das Ziel dieser Arbeit, die Lateralität als potentiellen Tierwohlindikator, zu untersuchen. Pferde dienten dabei als Model-Organismen, denn sie zeigen sensorische und motorische Lateralität. Ihre sensorischen Organe sind lateral positioniert, non-invasive Stresshormonanalysen sind bereits etabliert und als sehr soziales Tier, leiden Pferde nicht selten unter den nicht angemessenen Haltungsbedingungen, die ihnen der Mensch bietet. Dies zeigt sich in unterschiedlichen Formen von Stressanzeichen und -verhalten. STUDY 1 zeigte, dass eine Verschiebung zu einer stärkeren Präferenz der rechten Gehirnhemisphäre im Zusammenhang mit erhöhten fäkalen Stresshormonkonzentrationen geschah. Nach Veränderung der Haltungsbedingungen von Gruppenhaltung zur Boxenhaltung, die einige natürliche Bedürfnisse einschränkte, zeigte sich eine Linksverschiebung in sensorischer und motorischer Lateralität. Dabei kam es direkt nach der Veränderung der Haltungsbedingungen zu einer Linksverschiebung in der sensorischen Lateralität, während die Linksverschiebung in der motorischen Lateralität erst nach einer Woche auftrat. STUDY 2 zeigte, dass die motorische Lateralität, gemessen als bevorzugtes Antrittsbein, mit den Cognitive Bias (Tierwohlindikator) korrelierte. Pferde, die mit dem rechten Vorderbein bevorzugt aus stehender Position starteten, näherten sich schneller einem neutralen Stimulus und zeigten damit einen positiven Cognitive Bias. Es gab keinen Zusammenhang zwischen der Weideschrittpräferenz oder der sensorischen Lateralität und dem Cognitive Bias. STUDY 3 zeigte, dass die linken sensorischen Organe nicht nur im negativen Kontext agonistischer Interaktionen, sondern auch im positiven Kontext affiliativer Interaktionen bevorzugt wurden. Diese Ergebnisse verdeutlichen, dass nicht nur die Richtung der Lateralitätsverschiebung, sondern auch der Kontext, in dem eine Lateralitätsverschiebung auftrat, von Bedeutung ist. STUDY 4 untersuchte eine neue Konservierungsmethode die das Sammeln von Kotproben zur Stresshormon- und Immunglobulin A - Analyse vereinfachen soll. Nach der Kotprobenahme ist es oft nicht möglich diese für die weitere Analyse unmittelbar einzufrieren und der Transport von gefrorenen Proben ist aufwändig. Die Studie zeigte, dass Kotproben in einem geschlossenen System (Zentrifugenröhrchen) mit Silikagel getrocknet werden können. Diese Methode sorgte für eine ebenso schnelle Trocknung innerhalb von 24 Stunden wie unter kontrollierten Bedingungen bei Raumtemperatur. Die neue und einfache Trocknungsmethode schützte Stresshormone vor dem enzymatischen Abbau und konservierte diese. Während der Trocknung zeigte hingegen Immunglobulin A eine Reduktion ihrer nachweisbaren Konzentration. Daher wird empfohlen, wenn möglich, auf die Trocknung von Kotproben zu verzichten, wenn Immunglobulin A analysiert werden soll. Ist dies nicht möglich, können die Daten extrapoliert werden. In STUDY 5 wurde untersucht, ob die Stärke der Lateralität Aufschluss über den physiologischen und immunologischen Status eines Organismus, dessen Stressantworten, Stressreaktivität oder dem Cognitive Bias gibt. Es zeigte sich nur ein Zusammenhang zwischen dem Alter der Pferde und der Stärke der Lateralität. Mit zunehmendem Alter nahm die Stärke der Lateralität zu. Die Ergebnisse verdeutlichten, dass die Stärke der Lateralität kein zuverlässiger Tierwohlindikator ist. Die Richtung der Lateralität scheint in diesem Zusammenhang von größerer Bedeutung zu sein. Zusammenfassend konnte gezeigt werden, dass die Lateralität ein vielversprechender, zuverlässiger, wiederholbarer und objektiver Tierwohlindikator sein kann, der mit weniger Zeitaufwand, kostengünstig und einfach zu beurteilen ist. Vergleichbar mit bereits etablierten Stressparametern hat auch die Lateralität als Tierwohlindikator ihre Grenzen. Daher wird empfohlen, zeitgleich andere Tierwohlindikatoren, deren Veränderungen, und die Veränderungen der Lateralität zu erheben. Denn unterschiedliche Eigenschaften und Charakterzüge verursachen eine hohe inter-individuelle Variation in den Basal Lateralitätsindizes. Es werden mögliche Einflüsse und Beziehungen zwischen emotionaler Informationsverarbeitung und zerebraler Lateralisierung diskutiert. Dennoch sind weitere Untersuchungen notwendig um zuverlässigere und standardisierte Messmethoden, insbesondere der motorischen Lateralität, zu etablieren und um den Zusammenhang zwischen emotionaler Informationsverarbeitung und Lateralität, sowie anderen möglichen Faktoren, zu verstehen

Sensory laterality in affiliative interactions in domestic horses and ponies (Equus caballus)

Many studies have been carried out into both motor and sensory laterality of horses in agonistic and stressful situations. Here we examine sensory laterality in affiliative interactions within four groups of domestic horses and ponies (N = 31), living in stable social groups, housed at a single complex close to Vienna, Austria, and demonstrate for the first time a significant population preference for the left side in affiliative approaches and interactions. No effects were observed for gender, rank, sociability, phenotype, group, or age. Our results suggest that right hemisphere specialization in horses is not limited to the processing of stressful or agonistic situations, but rather appears to be the norm for processing in all social interactions, as has been demonstrated in other species including chicks and a range of vertebrates. In domestic horses, hemispheric specialization for sensory input appears not to be based on a designation of positive versus negative, but more on the perceived need to respond quickly and appropriately in any given situation.Publisher PDFPeer reviewe

Evidence for Right-Sided Horses Being More Optimistic than Left-Sided Horses

An individual’s positive or negative perspective when judging an ambiguous stimulus (cognitive bias) can be helpful when assessing animal welfare. Emotionality, as expressed in approach or withdrawal behaviour, is linked to brain asymmetry. The predisposition to process information in the left or right brain hemisphere is displayed in motor laterality. The quality of the information being processed is indicated by the sensory laterality. Consequently, it would be quicker and more repeatable to use motor or sensory laterality to evaluate cognitive bias than to perform the conventional judgment bias test. Therefore, the relationship between cognitive bias and motor or sensory laterality was tested. The horses (n = 17) were trained in a discrimination task involving a box that was placed in either a “positive„ or “negative„ location. To test for cognitive bias, the box was then placed in the middle, between the trained positive and negative location, in an ambiguous location, and the latency to approach the box was evaluated. Results indicated that horses that were more likely to use the right forelimb when moving off from a standing position were more likely to approach the ambiguous box with a shorter latency (generalized linear mixed model, p < 0.01), and therefore displayed a positive cognitive bias (optimistic)

Laterality in Horse Training

For centuries, a goal of training in many equestrian disciplines has been to straighten the horse, which is considered a key element in achieving its responsiveness and suppleness. However, laterality is a naturally occurring phenomenon in horses and encompasses body asymmetry, motor laterality and sensory laterality. Furthermore, forcibly counterbalancing motor laterality has been considered a cause of psychological imbalance in humans. Perhaps asymmetry and laterality should rather be accepted, with a focus on training psychological and physical balance, coordination and equal strength on both sides instead of enforcing “straightness”. To explore this, we conducted a review of the literature on the function and causes of motor and sensory laterality in horses, especially in horses when trained on the ground or under a rider. The literature reveals that body asymmetry is innate but does not prevent the horse from performing at a high level under a rider. Motor laterality is equally distributed in feral horses, while in domestic horses, age, breed, training and carrying a rider may cause left leg preferences. Most horses initially observe novel persons and potentially threatening objects or situations with their left sensory organs. Pronounced preferences for the use of left sensory organs or limbs indicate that the horse is experiencing increased emotionality or stress, and long-term insufficiencies in welfare, housing or training may result in left shifts in motor and sensory laterality and pessimistic mentalities. Therefore, increasing laterality can be regarded as an indicator for insufficiencies in housing, handling and training. We propose that laterality be recognized as a welfare indicator and that straightening the horse should be achieved by conducting training focused on balance, coordination and equal strength on both sides

Basic Needs in Horses?—A Literature Review

Simple Summary All animals have requirements that are essential for their welfare, and when these basic needs are not met, the animal suffers. In horses, it is claimed that these needs include social contact, social companionship, free movement and access to roughage in the form of grass, hay and/or straw. To validate this claim, this review examines 38 studies that reported on horses' responses when one or more of these factors are restricted. We categorised the type of responses investigated: (a) Stress (e.g., increased stress hormones), (b) Active (e.g., increased aggression), (c) Passive (e.g., depressive-like behaviour) and (d) Abnormal Behaviour (e.g., stereotypies), and analysed the frequencies with which the investigated responses were shown. Overall, the studies reported that horses did react to restrictions in the described basic needs, especially to combinations of restricted social contact, free movement and access to roughage. The observation of passive responses and the development of abnormal behaviour provided compelling evidence that horses were suffering under these restrictions, and existing abnormal behaviours indicated that they had suffered at some time in the past. We conclude that the literature supports the claim that social contact, free movement and access to roughage are basic needs in horses and need to be taken into consideration to ensure their mental and physical welfare in management and training. Every animal species has particular environmental requirements that are essential for its welfare, and when these so-called "basic needs" are not fulfilled, the animals suffer. The basic needs of horses have been claimed to be social contact, social companionship, free movement and access to roughage. To assess whether horses suffer when one or more of the four proposed basic needs are restricted, we examined several studies (n = 38) that reported behavioural and physiological reactions to these restrictions. We assigned the studies according to the four types of responses investigated: (a) Stress, (b) Active, (c) Passive, and (d) Abnormal Behaviour. Furthermore, the number of studies indicating that horses reacted to the restrictions were compared with the number of studies reporting no reaction. The limited number of studies available on single management restrictions did not allow conclusions to be drawn on the effect of each restriction separately, especially in the case of social companionship. However, when combinations of social contact, free movement and access to roughage were restricted, many of the horses had developed responses consistent with suffering. Passive Responses, indicating acute suffering, and Abnormal Behaviour, indicating suffering currently or at some time in the past, were especially clearly demonstrated. This provides further evidence of the usefulness of assessing behavioural parameters in combination with physiological measurements when evaluating horse welfare. This meta-analysis of the literature confirms that it is justified to claim that social contact, free movement and access to roughage are basic needs in horses

Sensory laterality in affiliative interactions in domestic horses and ponies (<i>Equus caballus</i>)

Many studies have been carried out into both motor and sensory laterality of horses in agonistic and stressful situations. Here we examine sensory laterality in affiliative interactions within four groups of domestic horses and ponies (N = 31), living in stable social groups, housed at a single complex close to Vienna, Austria, and demonstrate for the first time a significant population preference for the left side in affiliative approaches and interactions. No effects were observed for gender, rank, sociability, phenotype, group, or age. Our results suggest that right hemisphere specialization in horses is not limited to the processing of stressful or agonistic situations, but rather appears to be the norm for processing in all social interactions, as has been demonstrated in other species including chicks and a range of vertebrates. In domestic horses, hemispheric specialization for sensory input appears not to be based on a designation of positive versus negative, but more on the perceived need to respond quickly and appropriately in any given situation

Single housing but not changes in group composition causes stress-related immunomodulations in horses

Domestic horses are currently often subject to management practices that can entail social stressors, which in turn can negatively influence immunocompetence and disease susceptibility. The present study therefore aimed to characterize the number of various blood leukocyte subsets in horses, focusing on two potentially stressful housing environments: changes in group composition and relocation to individual stabling. Immune measurements were conducted before as well as one and eight days after changes were made. They were complemented by an assessment of plasma cortisol concentrations as well as behavioral observations. One and eight days after relocation to single housing, the mean numbers of eosinophils, T helper cells and cytotoxic T cells decreased by up to 31%, 20% and 22% respectively, whereas the mean numbers of neutrophils increased by 25%. In contrast, one and eight days after changes in group composition not only the mean number of neutrophils, but also of monocytes, T helper cells and cytotoxic T cells increased by up to 24%, 17%, 9%, and 15% respectively. In consequence, an increase in the neutrophil-to-lymphocyte ratio indicating stress-induced immune modulation was found after relocation to single housing, but not after changes in group composition. The changes in leukocyte numbers after relocation to single housing were accompanied by a transient increase in cortisol concentrations after one day and the occurrence of disturbed behavior patterns one week after change in housing condition. In contrast, changes in group composition did not result in an increase of cortisol concentrations or in an increase of aggressive interactions. The results strongly indicate that individual stabling is an intense stressor leading to acute and lasting alterations in blood counts of various leukocyte types. The study highlights a probable negative impact of single housing on welfare and health of horses and an advantage of group housing systems in view of immunocompetence

Preservation of fecal glucocorticoid metabolites and immunoglobulin A through silica gel drying for field studies in horses

Stability of stress hormone metabolites, fecal glucocorticoid metabolites (FGMs), and immunoglobulin A (IgA) was evaluated in horse feces dried in an air tight tube on silica gel, for improving stress analysis with fecal samples collected under field conditions with uncontrollable humidity. IgA showed a significant loss, but FGMs were stable and appeared to be reliably preserved. Non-invasive methods enable stress evaluation through measuring fecal glucocorticoid metabolites (FGMs), and immunoglobulin A (IgA) in the feces avoiding stressful blood drawing or stressful restraining of animals in the field. However, FGMs and IgA are mostly analysed in freshly frozen samples, which is difficult when fresh samples cannot be frozen immediately or frozen samples cannot be stored or transported. Good results were also derived from air-dried fecal samples, which are hampered by unstable air humidity in the field. These difficulties may be overcome, when drying of samples could be induced with colorless silica gel (SiO2) granules in a secure set-up, such as an air tight tube. We determined the speed of drying 1.5 g of a fresh fecal sample from six horses on air and on silica gel. Furthermore, FGMs and IgA were analysed in differently stored subsamples from 12 horses: in frozen fecal samples, in air- or silica gel-dried samples stored for 1 day and for 7 days, and in wet fecal samples kept in a tube at room temperature for 7 days. FGM levels remained stable in feces dried on air or on silica gel for 7 days, whereas IgA quantities showed a significant loss. Under field conditions, when freezing or transporting the frozen samples is not possible and humidity hampers air drying, drying samples on silica gel in air tight tubes appears to be very helpful and reliable for analysing FGMs

Does Carrying a Rider Change Motor and Sensory Laterality in Horses?

Laterality in horses has been studied in recent decades. Although most horses are kept for riding purposes, there has been almost no research on how laterality may be affected by carrying a rider. In this study, 23 horses were tested for lateral preferences, both with and without a rider, in three different experiments. The rider gave minimal aids and rode on a long rein to allow the horse free choice. Firstly, motor laterality was assessed by observing forelimb preference when stepping over a pole. Secondly, sensory laterality was assessed by observing perceptual side preferences when the horse was confronted with (a) an unfamiliar person or (b) a novel object. After applying a generalised linear model, this preliminary study found that a rider increased the strength of motor laterality (p = 0.01) but did not affect sensory laterality (p = 0.8). This suggests that carrying a rider who is as passive as possible does not have an adverse effect on a horse’s stress levels and mental state

Nursing Case Report in Patient after right Breast Reconstruction with Abdominal Flap at the Departement of Plastic Surgery

<p>A: CLDN2; B: CLDN12; C: OCLN; D: ZO1.</p