If your horse has been eating very sparse pasture or has been eating hay all winter it will need to be introduced to lush pastures very gradually. An abrupt change in the feed can cause colic, laminitis or founder. Ponies, overweight horses, senior horses and some draft breeds or draft crosses seem to be particularly susceptible although any horse can be affected. A pony can founder on rich grass in less than an hour of grazing time.
If your horse or pony is grazing a pasture from the time the ground thaws in early spring, he will be introduced to the new growth of grass naturally. Many people keep herds of ponies this way without a problem. However, if you make the switch from a hay diet to lush growing grass suddenly problems can occur.
Many pony breeds evolved in areas of very sparse pastures, like mountainous and arid regions where grass doesn’t grow thickly. Ponies would have had to spend their grazing time searching and navigating rugged terrain. Our thickly grassed pastures make grazing too easy for most ponies. Therefore, you have to be really careful to introduce grass slowly and watch they aren’t eating too much
Allow ponies a few minutes of grazing, gradually building the time spent. Gradually increase the time until you are satisfied the pony can spend all day out on pasture. Ponies gain weight really easily though. You may find that you have to restrict the grazing time of ponies because they gain weight quickly. Founder is very common in ponies, and obesity can lead to problems such as metabolic syndrome. So leaving your pony out on pasture all the time may not be possible. Let your pony graze for very short periods of time and then leave them in an area with very sparse grazing. Your pony will no doubt try to convince you its starving, but you’re the best monitor of its actual condition.
Horses put out on lush problems can have immediate problems and can also be prone to metabolic syndrome and founder. Introduce your horse gradually, starting with a half-hour and adding about ten minutes every day until you can leave the horse for the day. You can also feed hay before the horse is turned out to prevent him gorging himself because he feels hungry. Keep in mind that having a completely empty stomach isn’t good either, as that can possibly lead to EGUS.
It’s tempting to turn your horse out in the spring and watch him enjoy that beautiful green grass. However, doing so may endanger his health, or be fatal. Err on the side of caution when introducing pasture.