Terceira parte de um artigo desenvolvido exclusivamente para este Blog pela Dra. Chiara Scopa e pelo Dr. Paolo Baragli, cientistas internacionais do departamento de Ciências Veterinárias da Universidade de Pisa na Itália que são especialistas em comportamento e bem-estar de cavalos.

 

3. Watch out those three: stereotypy, apathy, depression

By the term stereotypy Mason (1991) referred to “repetitive, invariant behaviour patterns with no obvious goal or function”. Many animal species display stereotypies in particular if the housing condition is poor in stimuli (cfr environmental stimuli in previous paragraph) or if they are not able to engage in social relationships with conspecifics. Let’s focus on these two elements: stimuli coming from the environment (1) and sociality (2). Those are in fact fundamental building blocks of living social animals and they must be considered as unavoidable requirements for a ‘happy life’ in stabled horses.

First, it must be said that all animals should have the means to be functional participants of their own housing environment, with the opportunity to modify it by specific behaviors (1). Through the learning process or by the evolutionary heritage of the species, animals ideally expect what kind of challenges and stimuli are going to face in their lifetime, from the environment. Therefore, when the ‘ideal’ stimulus comes from the real world, a match should be found between what individuals have been preparing to manage in the environment and what they are actually facing. A realistic example: feline cubs are trained to hunt (learning process from their mother) and at the same time, they are equipped by species evolutionary history with appropriate hunter claws; when it comes to real challenge from environment (hunting), cubs can find a correspondence with what they are trained to do and what the challenge is requiring, that is putting into practice what learning and evolution have teaches and provided (i.e. using claws). A lack in this correspondence may actually cause a form of frustration (I cannot manage this situation with what I have/know!).

In this perspective, the parameter used in stables should be giving horses the chance to appropriately manage and solve all the possible situations they could bump into (as for thirst, hunger, cold or hot, but also the possibility to sniff and explore every new element introduced in the box).

Nevertheless, sometimes an apparently unsolvable task may motivate to find a solution even more than a solvable one! That is the reason why the presence of new stimuli is employing in stabled horses as an exercise to develop investigative behaviors, which are considered reliable indicators of welfare (the so called environmental enrichment). The interest toward something currently present in the environment appears by curiosity, exploration and attentive behaviors; arousal represents a byproduct of interest. Following Izard’s (1997) reasoning, interest leads to selective attention toward a specific stimulus that in turns causes exploration and manipulation of the stimulus itself. Satisfaction, pleasure or arousal indeed comes from tactile manipulation. That’s why those surroundings, in which an animal does not have the opportunity to physically interact with the environment, may cause negative emotional states in the subject.

The problem arises when the challenge is effectively unsolvable. At that point a common stress condition may rapidly escalate into the display of serious abnormal behaviors. Incompatibility with other members of the same social group, lack in space or in resources represent some possible sources of frustration in horses; these kind of situations could lead to a climax of anxiety (I cannot figure out how to solve this) up to a total apathy (I know  cannot solve this, so I don’t even try). Therefore, some forms of apathy or stereotypies are often linked to an impoverished stabled condition and to a neglected attitude of caregivers.

It has been hypothesized that when horses experience conditions where they have no control over aversive stimuli they turn into a phenomenon called learned helplessness (Hall et al., 2008). Learned helplessness is a psychological illness in which subjects learn that their behavior is not appropriate to handle the stimuli coming from the environment. This deficit may show up in association with a reduction in spontaneous behavior and increased sympathetic activity (Pryce et al., 2011; Baragli et al., 2014).

Apathetic or even depress horses are those who do not react to environmental stimulation and which Fureix and colleagues (2012) defined “withdrawn” horses. A withdrawn horse is almost totally motionless: neck, head and ears are static meaning that he/she is not interested in what or who is present around; the neck is stretched and there is similar height between neck and back; the eyes are opened appearing as “dull eyes looking nowhere” (Burn et al., 2010); the ears are held in a backward position. When compared to not-withdrawn horses, the withdrawn ones do not react to human contact or tactile stimulation even when both depressed and not depressed animals come from the same stable. In a following study Fureix and colleagues (2015) reported that withdrawn horses generally consume less saccharose. In human patients this feature (ascribable to anhedonia, the loss of pleasure through, for example, food) is considered a key symptom of depression. Hence, it could be said that there is a physiological correspondence with behavioral definition of depressive-like states in horses. Moreover nowadays we know that repeated negative experiences (involving the emotional sphere of the individual) may influence in the long term the way in which animals process environmental information; this in turns makes individuals less conscious about positive stimuli and more sensitive to the negative ones.

Beside the scarce stimuli in surroundings, social isolation is another potential source of stress in horses (2). During the last decades many scientific studies (Crowell-Davis et al., 1985; Houpt et al., 1986; Van Dierendonck et al., 1996) emphasized the importance to dedicate some precise moments of the day to social relationships, foraging or locomotor behaviors in feral horses populations. Life in stable limits the possibility to display locomotor activity and also other numerous behaviors, thus enhancing the stress levels in animals. A Kiley-Worthington’s work (1990) explained how horses living in single box, without the possibility to interact with others and following a programmed feeding schedule, spend the 65% of the day resting on foot. This value is three times superior to the percentage of hours spent in resting position by feral horses, who dedicate the 60% of the day foraging around the area, against the 5% of stabled horses. All these differences may be lead backs to the restricted space condition of single boxes and of course, to the implied social isolation from which a series of criticalities originates: physical limitation, reduced environmental stimuli, decreased possibility to engage in specific behaviors.

Visser and collaborators (2008) compared a group of horses stabled in single boxes with horses stabled in double boxes. Horses from the first group could hear and smell other individuals and eventually answered to them, but only those in the second group could bodily interact with a companion. Authors reported the differences of behavioral and physiological stress-indicator behaviors between horses in both conditions, pointing out that the total absence of social interaction may indeed contribute to the display of some abnormal behaviors. As a matter of fact 67% of single stabled horses developed 12 different types of stereotypies, whereas none of those living ‘in company’ displayed any stereotypy. Visser and collaborators recorded a specific stereotypy commonly called weaving, consisting of the repetitive lateral swaying of the head, neck, forequarters and sometimes hindquarters of the horse (as defined by Nicol, 1999). It has been even hypothesized that this behavioral pathology may derived from repetitive attempts to reach and contact another individual (from a side to another), confirming the pivotal role of social component in a horse’s life.

In conclusion, ethical sense, critical observation and behavioral science must have a common purpose that is accomplish an updated horse-management code which takes into account horse natural attitude, its cognitive level and its needs.

 

REFERENCES:

Mason, G. J. 1991 Stereotypies: a critical review. Animal behaviour 41, 1015-1037

Izard, C. E. 1997 Emotions and facial expressions: A perspective from Differential Emotions Theory. The psychology of facial expression 2, 57-77

Hall, C., Goodwin, D., Heleski, C., Randle, H. & Waran, N. 2008 Is there evidence of learned helplessness in horses? Journal of Applied Animal Welfare Science 11, 249-266

Pryce, C.R., Azzinnari, D., Spinelli, S., Seifritz, E., Tegethoff, M. & Meinlschmidt, G. 2011 Helplessness: a systematic translational review of theory and evidence for its relevance to understanding and treating depression. Pharmacology & Therapeutics 132: 242-267

Baragli, P., Vitale, V., Banti, L. & Sighieri, C. 2014 Effect of aging on behavioural and physiological responses to a stressful stimulus in horses (Equus caballus). Behaviour 151, 1513-1533

Fureix, C., Jego, P., Henry, S., Lansade, L., & Hausberger, M. 2012 Towards an ethological animal model of depression? A study on horses. PLoS One 7, e39280

Burn C. C., Dennison T. L., Whay H. R. 2010 Relationships between behaviour and health in working horses, donkeys, and mules in developing countries. Applied Animal Behaviour Science 126, 109–118

Fureix, C., Beaulieu, C., Argaud, S., Rochais, C., Quinton, M., Henry, S., Hausberger, M. & Mason, G. 2015 Investigating anhedonia in a non-conventional species: Do some riding horses Equus caballus display symptoms of depression? Applied Animal Behaviour Science 162, 26-36

Crowell-Davis, S. L., Houpt, K. A., & Carnevale, J. 1985 Feeding and drinking behavior of mares and foals with free access to pasture and water. Journal of animal science 60, 883-889

Houpt, K. A., O’Connell, M. F., Houpt, T. A., & Carbonaro, D. A. 1986 Night-time behavior of stabled and pastured peri-parturient ponies. Applied Animal Behaviour Science 15, 103-111

Van Dierendonck, M. C., Bandi, N., Batdorj, D., Dügerlham, S., & Munkhtsog, B. 1996 Behavioural observations of reintroduced Takhi or Przewalski horses (Equus ferus przewalskii) in Mongolia. Applied Animal Behaviour Science 50, 95-114

Kiley-Worthington, M. 1990 The behavior of horses in relation to management and training towards ethologically sound environments. Journal of Equine Veterinary Science 10, 62-75

Mills, D.S. & Clarke, A. 2002 Housing, Management and Welfare. In: N. Waran ed.: Welfare of Horses. Kluwer Academic Publishers

Baragli, P., Paoletti, E., Pacchini, S., Martelli, F. & Sighieri, C. 2009 Influenza di un protocollo di arricchimento ambientale sul comportamento dei cavalli in scuderia. Ippologia 20, 23-33

Visser, E. K., Ellis, A. D., & Van Reenen, C. G. 2008 The effect of two different housing conditions on the welfare of young horses stabled for the first time. Applied Animal Behaviour Science 114, 521-533

Nicol, C. 1999 Understanding equine stereotypies. Equine veterinary journal 31, 20-25