Long grass versus short grass – which is better?

If you have a ‘good doer’ - a horse or pony who puts on weight easily - and you worry about how much and what type of grass you should give them, this subject may have crossed your mind.

You may have read that short grass is rich, full of sugars and is not suitable for horses and ponies. You may also have read that long, mature grass is safe and that good doers can be given free access.

Both of these are incorrect, and you can read on for an explanation of why, and also to find out how to ensure your horse or pony has access to grass that is suitable for them.

It’s not actually about long vs short

It’s not about the length or maturity of grass, or even the amount of sugar or other nutrients per kilo. What matters to the grazing horse is the total amount of nutrients – including sugar and fructan which are called water soluble carbs (WSC) – that are eaten and the rate at which they are eaten.

That is why short, overgrazed grass - which may be higher in sugar and calories per kilo than longer, more mature grass – is likely to provide more appropriate grazing for a good doer (who does not wear a grazing muzzle). The reason the short, overgrazed grass might be better is that the grazing horse or pony gets less nutrients (less sugar, less calories) per hour of grazing from the short grass, compared to the longer, stemmier grass.

The horse on overgrazed, sprouting pasture will likely need more fibre e.g. from a small strip of longer, stemmier grass and/or supplementary forage like soaked hay, but grazing very short grass is sometimes the only way to keep a good doer slim and healthy (if they don’t wear a grazing muzzle).

Most good doers on free access to longer, mature grass will put on weight and store excess body fat, over time. There are a few exceptions, and now and again an owner will delight in telling me about these, but I have many more owners who have contacted me for help after their horse or pony became obese kept on free access to longer, more mature grass.

Many factors are involved

Grass pasture is unpredictable and the both the amount of grass and the nutrients it supplies the grazing horse – both WSC and calories – depends on a number of factors including temperature, rainfall, soil, season, species of grass and other plants in the pasture, and grazing pressure.  Grass produces simple sugars via photosynthesis and once these are produced at levels higher than the plant’s current needs, it stores them as fructan. Fructan is not classed as sugar because it is digested quite differently by the horse.

We do not fully understand the implications of fructan and sugar intake on the horse and levels of both can fluctuate widely (over hours) in grass pasture. These carbs are digested quite differently in the horse’s gut and although both contribute to calorie intake, they may affect gut health and/or insulin levels (and therefore, potentially, laminitis risk) differently. Horses and ponies affected with insulin dysregulation (ID) respond quite differently to WSC intake compared to non-ID individuals, so this is another factor to consider.

A disadvantage of grazing mature, stemmy grass that has gone to seed is the higher load of mycotoxins it contains versus shorter, leafy grass so this is something to consider in the autumn and over winter. We should never assume that dead-looking mature grass has ‘nothing left in it’ because not only can it supply plenty of calories, researchers have shown that it may also supply significant levels of WSC.

I believe we also need to consider the impact of our grazing on the environment as well as the needs of our horses and ponies, and this can be a difficult balance in practice. (Perhaps a subject for another blog). Using a grazing muzzle on a good doer can be way of keeping both grass pasture and horse heathy. The pasture does not get over-grazed, and the horse or pony remains a healthy weight.

How do we choose which type of grazing for our horse?

The key for an individual horse or pony is to monitor them carefully and adjust their grass access according to their bodyweight and condition (fat covering) and any signs of excess grass intake e.g. green sloppy dropping, changes in footiness (foot sensitivity), raised digital pulses (which could be a sign of laminitis) or body fat gain. In practice, this is the best strategy that maintains good health and a healthy bodyweight in an individual horse or pony.

Apps that predict ‘danger’ level of grazing should not be relied upon without careful assessment of the individual, since these are only predictive to the area according to weather conditions, and not to the specific pasture and do not take into account the specific horse or pony. For example, research has shown higher WSC levels in grass growing in full sun, compared to that in the shade e.g. under trees.

Some horses and ponies stay healthy on regular grass pasture without any issues, and those in regular, moderate to hard work (exercise) who have a slim body condition are more likely to. Many horses and ponies will however put on unhealthy amounts of weight (body fat) on regular grass pasture and long, more mature grass, and may benefit from being kept on very short grass. The alternative is a grazing muzzle and regular grass pasture (which would be around 5 to 10cm long).

In conclusion, we need to be aware of the complexity of grass for horses and ponies, and remember that most if not all of the ideas, opinions and advice we read about from all sorts of sources are best-guesses and not well proven.

There are a number of factors to consider when deciding on whether to graze our horses and ponies on short or long grass, but ultimately we will get the best results by monitoring our individual horses and ponies carefully and regularly, and adjusting their pasture grass accordingly.