Start ‘em young, treat ‘em right: How horses’ early life experiences can set them up for success in life

Abstract

At what age is a horse ready to be trained and ridden? The answer to this question—which has long been debated—has become more complex in recent years as concerns that were historically based almost solely on horses' physical capacity have been replaced by a growing emphasis on their mental welfare. At a workshop held at the Jockey Club, Newmarket and co-hosted by Beaufort Cottage Educational Trust and the Graf Lehnsdorff Institute for Equine Science, this subject was discussed with a wide range of stakeholders.

The recognition that evaluation of animals' welfare should be based primarily on how they feel has numerous consequences. It is feeding into assessment of the ethical implications of all that we do with and to animals. It is affecting the public's opinion of equestrianism—the sport's so-called ‘social licence to operate’. And it is influencing legislation. A pertinent example is the German government's recent introduction of legislation¹ that makes it illegal to train or compete a horse that is <30 months of age—with a temporary derogation for racing pending the results of ongoing research. All those who would like equestrian sport to continue as a legitimate enterprise should take particular note of this last point, given the strong link between public disaffection with an endeavour and ensuing restrictive legislation.²

Currently, within equestrianism, the most popular framework for assessing an animal's welfare is the five domains model.³ This model (Figure 1) encourages us to interpret the animal's experience in each of four physical/functional domains within the context of how this impacts their mental state. It recognises that although physical health is undoubtedly important, other factors should be given similar consideration as they are also able to affect how an animal feels. This holistic overview of how an animal feels about multiple aspects of their life allows us to assess the balance of their positive and negative mental states—an important consideration given the growing demand from welfare scientists, the public, and many of those within equestrianism that horses live ‘good lives’,^4-7 rather than those that are merely ‘lives worth living’.

Given the growing focus of both welfare scientists and the public on animal sentience and mental welfare, in this editorial we will set aside any discussion of horses' physical readiness for training and competition and concentrate instead on their mental maturity.

Before we can discuss horses' mental readiness for training, we need to consider what the term ‘mental maturity’ actually means in this species. Horses' cognitive abilities and emotional drivers are very different from those of humans so we cannot just import concepts from human work. This is partly because humans (and a number of species with which many of us choose to spend our time, including dogs) are altricial. This means that they are born in an underdeveloped state that is characterised by, among other things, limited learning capacity and an early socialisation phase during which the fear response is limited. In contrast, horses are precocial and so, relatively speaking, they are born with an advanced cognitive ability. Within hours of birth they need sufficient cognitive capacity to be able to learn how to interact with their environment, and any other species they may encounter, in order to survive. Evolutionary pressure has driven fear as a prominent emotion: better to run first and learn later to habituate to a non-threatening stimulus, than to be eaten. This aligns with the absence of a fear-limited socialisation period in this species. Therefore, although foals' early cognitive ability means that they can be trained using learning theory from a much earlier age than puppies, habituating them to humans and the environment is more difficult.

We suggest that a horse's level of mental maturity should be defined as their ability to manage their innate emotions in a given context. This will be reflected in the behaviours they display. If their level of mental maturity is sufficient for the situation with which they are presented, they should be able to at least cope, and preferably have a positive mental experience. Ideally, they will learn from each novel experience that they have, becoming more confident and resilient to stress in increasingly challenging situations—and therefore more mentally mature over time. At any given age, mental maturity will differ among individuals and is likely to be influenced by the same factors that influence personality, including genetics, prior life experiences, current environment/management and innate temperament.⁸

What can we do to help them do this successfully?

As a species, horses are primed for fear (the emotional response to a specific and present perceived threat) and anxiety (the more generalised emotional response to non-specific and not currently present perceived threats), both of which drive a physiological and behavioural stress response. Horses that innately experience higher levels of fear and anxiety will clearly have worse mental welfare than those that do not. They are also less likely to thrive as sport horses due to the negative impacts of these emotions on learning ability—a topic that we discuss below. So, is there anything we can do to influence horses' levels of fear and anxiety?

Data from studies involving humans, horses and non-equid species suggest that the answer is ‘yes’. We know that the early life experiences of animals, including humans, have a profound effect on their health and behaviour as adults. The experiences that shape their lives start before they are born and may affect not only them, but also their offspring. The evidence that supports these effects is stronger for humans and non-equid animals than for horses, but the latter is growing slowly.

Neurophysiological development is influenced by stress, with early life experiences affecting brain function via epigenetic changes that occur in response to external factors. These changes, which are both stable and heritable, may occur in utero, when the animal is an infant, and during adolescence. In addition, physiological and biomolecular studies show that exposure to chronic stress alters the development and subsequent function of the nervous, endocrine and immune systems.^{9, 10} This in turn has negative impacts on cognitive, social and emotional functioning.¹⁰ Data from humans and farm/laboratory animals, in which the evidence for these effects is strongest, are discussed below.

A systematic review and meta-analysis found that, in humans, multiple adverse childhood experiences (ACEs) are a major risk factor for many health conditions and problematic behaviours.⁹ Interestingly, the outcomes most strongly associated with multiple ACEs (violence, mental illness and substance abuse) were all behavioural rather than physical in nature.

In animals, exposure in early life to a painful procedure such as disbudding, castration, tail docking, or beak trimming can result in short-term negative impacts on pain sensitivity, fear, anxiety, learning ability, social skills and ability to cope with stress.¹¹ To date, the impacts of these procedures on animals' adult lives have only been studied in rodents, with lifelong deleterious consequences reported.¹¹ Further work is needed to evaluate the impact of adverse early life experiences on horses during development and into adulthood.

Both human and animal work also shows the impact of good parental care on mammals' later lives. In rats, where cross-fostering was used to separate out genetic influence, the quality of maternal care impacted the epigenetic programming of the hypothalamic-pituitary-adrenal (HPA)-axis in the offspring as adults, with better care associated with lower stress responses.¹² This highlights the importance of a nurturing mother in helping young animals to feel safe. Likewise, dairy calves that were individually housed (i.e., socially isolated) showed greater fearfulness and lower capacity to learn than those that were group housed.¹³ In humans, losing a parent due to divorce, death, or abandonment is one of 10 recognised ACEs.¹⁴

These links between the presence and quality of maternal care and animals' subsequent cognitive ability and personality may be relevant in terms of current equine weaning practices—practices that leave substantial room for improvement and should be taken seriously as one of the most stressful experiences a horse will encounter. However, this is only one potentially adverse event among many that most young horses undergo. A short list might include initial halter training and handling, sales rings, relocation to new premises, mixing with unfamiliar conspecifics, transport, backing under saddle, and exposure to novel environments such as a racecourse or competition venue. In all of these experiences, the mental experience of the horse is likely to be related to the techniques used by, and attitude of, the handler. So, we have a duty to ask ourselves: Are management and training techniques that are currently standard across the industry increasing the risk that horses will display unwanted behaviours in later life?

These data all support a deleterious effect of maternal stress during gestation on the physiological and/or behavioural traits of young animals. Research is needed to determine which aspects of pregnant mares' personality and management influence their foals' stress response and behaviour.

Learning is a fundamental part of any sport horse's life. It may therefore be relevant that increased fear, pessimism, and stress are associated with reduced learning capacity in a range of species. Research into the factors that affect learning in horses is not yet extensive. However, Christensen et al. showed that in horses exposed to a stressful environment, fearfulness was associated with reduced learning performance.²² This is further illustrated by the results of a prospective study in which foals that were inherently more fearful showed lower ability to learn at both 5 months and 1 year of age than those that were inherently more bold.²³ It is worth noting that whilst the bold foals learned to step away from a pressure cue on their side, the more fearful foals did not and increasing pressure was required to elicit the desired response over time. This trait is likely to be detrimental when training for ridden work (Figure 2).²³

Overall, therefore, the evidence that we have to date suggests that minimising stress and maximising confidence in foals and adolescents will lead to improved learning ability and greater resilience to stress later in life—along with, as a corollary, the potential for better lifelong mental welfare.

The biggest ‘knowledge gap’ in this plan is that, in order to establish whether an individual horse is having a positive mental experience in a given context, we need to be able to reliably assess how they feel. This is a field that is growing rapidly but in which gaps currently exist, especially in terms of identification of positive emotions. Whilst acknowledging this, we should not let perfect be the enemy of good: the current level of understanding among veterinary behaviourists and welfare scientists is more than adequate to manage and train horses in a way that would allow most to live a good life. On this basis, further work should be undertaken in the field of human behaviour change: how do we facilitate meaningful changes within the equine sector to improve equine welfare and, as a consequence, strengthen our social licence?

In ending, we come back to the question we posed at the start of this article: ‘At what age is a horse ready to be trained and ridden?’. Based on cognitive ability alone, this is likely to be earlier than when they are physically ready. More importantly, however, we should approach this question from the perspective of each individual horse's level of mental maturity. Considering the evidence cited above, we would contend that the likelihood of a horse thriving mentally in sport depends primarily on their early life experiences and how they were raised and trained, and that this is probably more important than the age at which that training is started. If we can optimise horses' subjective experience of their lives—in other words, their mental welfare—and if objective and validated assessments show that their experiences are largely positive, we will have gone a long way towards being able to answer ‘Yes’ to the perfectly valid question of whether it is ethical to use horses in sport.

Gemma Pearson: Conceptualization; writing – original draft; writing – review and editing. Janet Douglas: Writing – review and editing; writing – original draft.