Laminitis is the second biggest cause of death in horses and ponies in the UK. This painful and debilitataing condition seems to creep up on us each year and I suspect 2008 will be no different. For the second year running we have had a late spring but the relief from winter regimes can be short lived if horses are allowed to over-indulge on lush green pasture. While our perception of this changeable weather may make us think that it is not particulary spring-like, the grass is responding to the long day-light hours and warmer wet weather by growing rapidly.
The high proportion of leaf to stem in spring grass allows it to capture the maximum amount of sunlight for photosynthesis and thus they become "little sugar factories" producing fructose,glucose,sucrose and fructans. Fructans are polymers of sucrose and fructose and are the way plants store excess sucrose when they are photosynthesising at a greater rate than they are growing. Fructans are un-digestible in the small intestine of the horse, but unfortunately are rapidly fermented in the hindgut. Any food that is rapidly fermented in the hind gut disturbs the normal balance of volatile fatty acid(VFA) production and generally causes an increase in lactic acid production. This starts the cascade of events:drop in hind gut pH, death of gram-ve bacteria, increased permeability of gut wall etc that all leads to laminitis.
Scientists have found that during our UK growing season anything that temporarily slows or stops growth will cause an accumulation of fructans in the grass. The main difficulty however, is predicting when this will occur. Our inclement weather patterns mean that the fructan accumulation / utilisation pattern can alter dramatically in one day and certainly changes from one day to the next. A more stable climate would make fructan accumulation more predictable, but unfortunatley we don't really have a climate in the UK we just experience weather! So we cannot rely on any predictive model to ensure that our horses are not consuming too much fructan. The only sure way of doing this is too limit access to grass. Many hard - working animals can graze lush grass with no detrimental effects, and in fact benefit from the additional condition that the grass gives them. However, the very fact that theses animals are working will mean a)thay are spending limited amount of time at grass and b)their energy demands are high so they will be using the energy from grass to fuel their work. Furthermore, these animals are unlikely to have the pre-disposing laminitic phenotype(look)of an apple bottom and cresty neck. This is more usually seen in the leisure / light working horses and ponies and it is these animals that are at risk at this time of year.
So what to do?
1.Limit access to grass. This can be done by simply reducing the time in the paddock or fencing off a small area and allowing them to graze that only or thirdly, fitting a grazing muzzle. The latter two measures are preferable as they allow the horse exercise and permit natural foraging behaviour.
2.During stabled periods, keep the gut moving(and them busy)by feeding some fibre, a bagged product is ideal here, especially one that has added mineral and vitamin balancers. It is a mistake to temporarily starve horses when thay are in as it interferes with gut physiology and just makes them gorge when they are returned to the field.
3.Reduce cereals at this time of year as the grass is full of accessible energy and protein and should be meeting the requirements of most horses in light work. However you should consider adding a daily vitamin and mineral supplement to ensure all your horses micronutrients are being met. This can be given with the fibre feed in the stable or as a free-access lick in the field.
4.If you have a horse that becomes sluggish in the hot weather and needs to be fed concentrates to keep the sparkle, then be sure to divide the daily ration into as many meals as possible. This is particulary important at this time of year as the hind gut will already be challenged with fructan and the last thing your horse needs is additional highly fermentable material (starch)entering the hind gut.
When feeding our horses, it is worth remembering that the horse is an athlete, a flight animal and was designed to roam the planes searching for food. It had to be sufficiently fit to be able to out-run predators while consuming enough to allow it to reproduce, feed young and store some fat for the winter. An over fat horse would just not have survived and we should remember this, particulary when presenting our pecious specimens in the show-ring. The majority of show judges recognise the difference between a well conditiond, muscled animal "fit for purpose" and will put these in front of over-weight horses in the line-up, but there are the few who still like to see "apple bottoms," cresty necks and barrel shaped middles. If your horse is put below one of these,console yourself with the fact that he or she is happy, healthy and will live to enter the ring next year.The "lump of lard" will inevitably succumb to painful laminitis and have a much reduced competitive career, would you want this for your horse?