No one could have predicted the length of the recent dry, hot spell and when it finally breaks it is likely to have direct effects on certain types of horse.

Despite high temperatures and low rainfall leading to parched land, grazing is not done for this season. In fact, grass being grass, it is awaiting its next big chance.

Although lack of water has stifled grass growth, especially in the central and eastern regions, it has not stopped the ongoing microbial activity within the soil.

One of the effects of this is the build-up of plant nutrients around the roots.
In addition, the soil is warm, so when the rain does finally arrive, there will be fantastic conditions for growth — plenty of food, warmth and moisture — all that grass can ask for.

Admittedly, the shortening days will limit the amount of grass that grows compared to other peak times such as May, but its effects should not be underestimated. You can have too much of a good thing.

Rapid late autumn growth will be of green, leafy grass, which is very high in nutrient value. For horses and ponies currently eating grass that is as dry as hay, or being fed hay because there is no grazing available, this will have two effects.

First, horses will eat the new growth because it will be far more succulent than the dry stuff. Second, this will constitute a rapid dietary change, which could cause metabolic upset if not managed correctly.

Laminitis, colic and tying up are all a real risk at this time, while young stock this could also lead to developmental physitis.

Feeding facts

  • Changing from four slices of hay to the equivalent in fresh grass will mean an estimated 35% increase in energy (calories), typically more than double the protein and almost three times the sugar.
  • A horse can munch through the grass equivalent of this amount of hay in less than half a day, or even a couple of hours if the grass is plentiful and he keeps his head down.
  • Depending on the grass and the growing conditions, sugar is stored in the form of fructans, which have been demonstrated scientifically to be capable of causing laminitis.
  • In exercising horses, such a shift in nutrient delivery, particularly of sugar-rich grass, could easily precipitate an episode of tying up due to overflow of sugar, not the usual culprit, starch, into the hindgut.
  • For horses and ponies being fed hay, you will know when the grass is growing because they will leave the hay. Watch them carefully and consider limiting the time at grass if you have a high-risk animal.