Spring aggression

Just read a post about a horse suddenly becoming aggressive and there possibly being a link to restricted grazing.

Several things may be happening diet wise - what immediately springs to mind are that magnesium uptake may be inhibited by spring grass and the horse may need some extra salt. If there is too much clover it may be short of iodine, so supplementing with iodised salt may be a good idea.

It may be uncomfortable and is anxious because of that or it may simply have too much energy from spring grass and is looking for ways to release it.

Fructans are sugars the horse cannot digest well and the grasses which store sugars in the form of fructans do so in the base of the leaf. Horses forced to graze short, stressed grass may be getting more fructan than is good for them. The havoc this causes in the hind gut may be setting the horse up for laminitis which can have a slow and insidious onset. The horse may be feeling sore long before we realise what the problem is.

The owner may know that the horse doesn't need extra food and in spring, but the animal's instincts are telling it to eat.  When we restrict grass in spring we have to compensate for that with high fibre substitutes to keep the horse's gut and mind happy - and healthy. We do not know enough about the interaction between the neuro-endocrine and peptidergic nervous systems to discount subtle imbalances within and between them as a reason for changes in behaviour.

The horse is instinctually primed to eat 16+ hours a day.  To get the energy it needs from the type of food it evolve to eat, it has to eat little and often. It is a trickle feeder - small stomach, long hind gut.

When it is eating it should be in a calm, relaxed frame of mind, head down, respiration slow and regular, heart rate low - and, producing saliva which contains enzymes that start off the digestion process and buffer the stomach and gut. The hormonal and peptide feed back systems maintain that frame of mind - all is well, keep eating.

If the horse is anxious (feels it is being deprived of food, feels threatened by others, is in discomfort etc) it is in an excited state. The pituitary gland is releasing factors that trigger the adenals to release adrenaline and cortisol in preparation for fight or flight. Heart rate and respiration go up - and critically, the mouth is dry because the horse has a relatively dry mouth when in flight mode.  Never underestimate the importance of saliva to a healthy digestion.

It's our fault that the horse gets access to soft leafed, NSC and legume rich pasture and doesn't get adequate movement so the evolutionarily driven need to eat almost constantly becomes a serious health issue. We need to ensure that the horse has grass substitutes - not fed to our convenience in a big pile of hay, but available in small amounts, almost all the time and in a way that encourages movement.

The basic advice always comes back to this - look to what nature's arrangements are and in what ways and to what extent your management of the horse differs from them. The horse cannot change its nature. It can and does accommodate itself to us to an extraordinary degree and it is a highly adaptable animal, BUT -  all animals have aspects of their physical and psychological being that are non-negotiable ie they are essential to the animal's wellbeing.  The adverse effects of these conditions not being met appropriately may be spectacular and sudden in onset, eg anaphylactic shock; or subtle and slow in onset, eg chronic laminitis, gut imbalances.

There is always a social component in the horse's behaviour because it is a highly social animal. It may be anxious about its place in the herd; it may be driven by its surplus energy to challenge other more dominant horses; it may be a social misfit that is always a nuisance in a large group but fine with one companion.

Horses reestablish herd bonds and hierarchy every day. We impose a huge stress on some horses when we keep them in a constantly shifting herd structure. Some cope very well - usually the calm confident types that every other horse wants to be with; and some go into extremely excited states - which, depending on a number of factors, may manifest as fearful nervous behaviour or overt aggression.

Finally - in trying to establish what the problem is for a given horse, be systematic. Eliminate one possible cause at a time so you can be reasonably certain what the trigger was.