While commonly seen, aggression over food is not normal horse behavior. This article will look at why this behavior exists in horses, what can be done to prevent it and why it is important you do so.
Aggression
By nature, horses are not an aggressive species. In free-ranging conditions they spend more time engaging in affiliative behaviors than they do in agonistic behaviors. Affiliative behaviors are ones that promote harmony between individuals, while agonistic behaviors are defensive or aggressive behaviors which serve to increase distance between individuals.
Behaving aggressively is a 'costly' endeavor: fighting burns precious calories; it carries with it the risk of injury or death; it can attract predators; it results in increased physical and psychological stress. For social animals like horses, who rely on others for safety, it also carries a real risk of damaging vital social bonds. Therefore, behaving aggressively is generally reserved for situations where an animal feels their survival may depend on it.
Resources
Resources are things generally necessary for survival. Animals may try to control resources by behaving aggressively - especially when that resource is in limited supply. In addition to food and water, resources may be such things as shelter or den sites, breeding partners, a large territory etc., depending on what that species needs to survive. While some species use aggressive behavior to control the resource food, horses living in natural conditions generally do not. This is because food is usually plentiful, and easily accessed. Even when food is scarce, horses tend to spread out rather than behave aggressively to control it. When free-ranging horses happen across a cache of a restricted resource such as water or salt, they tend to gather around the resource and engage in shoving behavior, not aggressive behavior, to access it.
Management practices that create stress around food
The practices that surround how a horse is raised and managed can shape how they behave when eating or being fed in the future. If eating has previously been associated with pain or stress, horses may behave aggressively towards others when food is present.
Horses are trickle feeders. They have evolved to eat small amounts of forage on a near-continual basis. Their GI system functions best when it is always processing forage. The horse's stomach continuously produces acid - about 1.5 liters every hour. When the stomach is empty, such as occurs during fasting, acid can easily splash up onto its top third. This area does not have a protective lining, and is very susceptible to the formation of ulcers.
The human practice of feeding 'meals', i.e., set hay feedings, can result in situations where horses quickly eat each meal, and then are subjected to an extended fasting period. A horse's 'chew' time should be approximately 18-20 hours per day, with a total combined fasting period of 4-6 hours (spread over a 24 hour period). When horses are fed set feedings that result in fasting these numbers may be reversed. For example, the meal-fed horse may have 4-6 hours of chew time, and 18-20 hours of fasting. Such fasting is both physically uncomfortable and psychologically distressing, and can negatively affect a horse's behavior.
Horses with ulcers may experience pain shortly after they begin eating. After a few episodes of this happening the horse may begin to feel conflicted about eating. While the horse wants to eat the food, the food causes them pain. Therefore, they may begin to behave aggressively when the food is delivered or if a person is nearby while they are eating.
Weaning practices can create involuntary negative associations for foals about food or being fed. Under natural conditions, the process of weaning begins at about 8-9 months of age. Unfortunately, it is common in the horse industry to prematurely wean horses at 4-6 months of age. At that age, a foal's digestive system isn't capable of fully utilizing forage alone, and therefore foals must be fed special concentrate diets in order to maintain their physical health. Prematurely weaned foals may be fed set feedings of concentrates, which results in the same issues for foals as adult horses fed set feedings. To complicate matters, premature weaning is stressful: foals don't just need physical nourishment from their dams, they also need psychological support. Stress plus sub-standard feeding practices can lead to the development of gastric ulcers. Premature weaning practices are also believed to be a contributing factor in the development of cribbing and other abnormal behaviors.
Horses without any issues around food may develop aggression at feeding time if exposed to horses who do feel stress or conflict about food. A previously well-adjusted horse may resort to using defensive behaviors to try and increase distance between themselves and an aggressively behaving horse. Repeat this scenario a few times, and the arrival of food begins to predict stressful events for all of the horses in the group.
Aggression towards people at feeding time
Horses may also display aggressive behavior towards people at feeding time. This can occur when food delivery by the person predicts stressful events, such as the ones mentioned above, or as a result of previous experience. For example, a person approaches with grain, the horse pins their ears, the person puts the grain down and retreats. From the horse's perspective, ear pinning resulted in food delivery. In such instances, it is crucial to determine the root cause of the ear pinning behavior and address that - rather than trying to suppress the behavior, using punishment. As discussed previously, a horse who is food-aggressive may have an undiagnosed ulcer, or may be being fed in ways that cause physical and mental distress.
When people use aggressive behavior themselves to move horses away during feeding or in an attempt to punish a horse's display of aggression, horses may respond in kind. While horses do need to be taught appropriate behavior when food is delivered, punishing aggression in this manner as a routine training practice is not recommended by equine behavior professionals. Such an approach can quickly backfire, resulting in an escalation of aggression from the horse; it may also create additional unwanted behavior problems.
People may believe that driving an aggressive horse away from food shows the horse the person is the leader. But this notion that horses have dominance hierarchies is very outdated and inaccurate information about how horses align themselves socially. This mindset towards human-horse interactions is also a contributing factor in the creation of numerous other behavior problems in horses. Driving a horse off of food only teaches the horse that people are aggressive, and unpredictable. It also fails miserably to consider the reasons the horse may be behaving aggressively in the first place.
Dealing with the horse who is aggressive at feeding time
When dealing with aggression at feeding time it's very important that two factors are considered before retraining can begin: 1. Pain must be ruled out and/or resolved. 2. Changes to the environment and/or feeding practices must be made to decrease stress which triggers aggressive behavior.
If pain has been diagnosed and treated by a veterinarian, the memory of pain being associated with food and/or being fed may linger. In such cases management changes and horse-friendly behavior modification techniques can be very effective in changing the horse's emotional response to being fed.
Changes to the environment include things such as: ensuring that there are more feeding sites than horses (e.g. 10 piles of hay to 5 horses), ensuring that forage is always available when horses are housed in groups, increasing the spacing between feeding sites, creating groups of compatible horses, separating horses to feed high-value food like grains etc.
It may also be important to utilize barriers (e.g. fences) between horses and people during retraining, to minimize the need for a person to behave aggressively or use punishment to stay safe. In general, it is simply not necessary to use punishment to address food-aggressive behavior in horses, nor is it advised by animal behavior specialists. Punishment can worsen aggressive behavior, and create additional unwanted behavior problems. Instead, equine behaviorists and horse behavior consultants use effective - and horse-friendly - methods to successfully resolve even the most serious cases of food-aggression in horses.
Summary
Equine behaviorists and horse behavior consultants take a multi-pronged approach to resolving food-aggression in horses: they determine why the horse is behaving aggressively, they address factors contributing to the behavior, and they teach the horse how they should behave instead.
Food-aggression in horses isn't normal behavior. Horses behaving aggressively around food are not only dangerous to be around, their behavior indicates that they are experiencing stress, and are unhappy. If your horse is food-aggressive, first have your veterinarian rule out physical or medical reasons for the behavior. Second, look at your management practices, and see how you can arrange things so that the horses never feel the feed to behave aggressively to control the food. Third, avoid the use of punishment in an attempt to end the behavior. Finally, if you need additional help contact a qualified equine behaviorist or horse behavior consultant to help you safely resolve the issue.