Why ‘Stage of Growth’ Matters ...persil grass affected!

Whatever species of grasses you have in your paddock, it is vital to understand how ‘stage of growth’ can directly affect your horses’ metabolism and therefore his performance.

Basically the younger the grass the more unbalanced it is with regard to some of the major minerals for your horse. Mature grass has used up these minerals and nutrients and converted them into the fibrous stalky parts of the plant which is much more suitable for horses to consume.


Luxury Uptake...

Grass grows from the base of the stem and the base of the leaves which is where the potassium and nitrogen (in the form of nitrates) accumulate. This is why short grass is ‘worse’ for horses than long grass.
The significant fact is that plants (pasture and crops) will take on board way more potassium than they actually need, a phenomenon known as ‘luxury uptake’.

On the other hand, unlike the livestock that graze it, grass has absolutely zero requirement for salt and hardly uptakes any at all. Horses actually have quite a large requirement for salt so when they are confined behind fences it is vital to add salt to their daily feeds rather than relying on a salt lick. Doing this has turned out to be the ‘nutritional tip of the century’ as it makes such a difference and is so cheap and easy!

If your horse is out on green grass 24/7 he is frequently in potassium and sometimes nitrogen overload at the same time as being deficient in salt. This is exacerbated when the horse sweats and loses even more salt.

Another nutrient that can cause big problems is excess nitrogen. This can come from too much clover, frequent harrowing or application of nitrogen fertilisers.

The roots take up nitrogen from the soil in the form of nitrates. It is transported to the leaves where it is eventually converted into protein and used for growth of the grass. When plants are stressed by drought, hot dry winds, hail or frost, or there is a lack of sunshine due to consecutive cloudy days this process is interrupted and excess nitrates accumulate at the base of the stem and the base of the leaves.

Immature plants will tend to have higher nitrate levels.
Ruminant livestock like sheep and cattle possess microbes in the rumen which facilitate the incorporation of nitrogen into protein molecules, the rest is converted to ammonia by the liver and excreted as urea in the urine.

Horses CANNOT utilize nitrogen in this way because they don’t have a rumen or the microbes. However nitrates (anions) still need to be excreted – which happens at the expense of other important minerals like magnesium.


Lush Grass...

Lush green grass is soft rather than stalky and full of water: up to 80%! Meaning there is very little fibre present, which as we all know is not good for the health of the hind-gut flora. It is also very high in ‘crude protein’ (meaning it has a high nitrogen content).

Lush grass has plenty of leaf area to photsynthesis and produce sugars. Consequently it is very palatable and horses will ingest large quantities in a short time!
Lush green grass contains plenty of chlorophyll, the central molecule of which is magnesium. You would think the greener the grass the calmer the horse! We know this isn’t how it works, in fact there are many interactions which need to be taken into account.

Mature Grass is by far the healthiest grass for horses to graze. The challenge is managing the pasture in order to have such grass ahead of the horses!
Not only is mature grass lower in potassium and nitrogen because it has finished growing, but studies have shown a progressive decline in photosynthesis (and therefore sugar production) with increasing age of the leaf. You still need to add salt as it is just as devoid in salt however you will not be subjecting your horse to a chronic potassium, and sometimes nitrogen, overload.

While horses evolved in the presence of a high iron intake resulting in their system only absorbing about 15% of what is consumed, they did not evolve in an environment of chronic potassium and nitrogen overload.

This is why the basis of our dietary recommendations is to be ‘mindful’ of potassium intake. Best not to add even more to the horses already high load by feeding legumes (clover and Lucerne, soy-bean meal, molasses, kelps). This is particularly the case when you live in cooler climates and your horse is grazing cool season grasses.

More in up-coming posts on how a diet of short green grass ruins large numbers of perfectly good horses and ponies!

PIC: Little Sushi suffered chronic laminitis on this short green grass.

More About Short Grass.....

As a general rule of thumb the ‘richer’ your grass the less time your horse can spend out there grazing. The poorer your grass the more hours per day he can spend out there grazing.

We have already talked about the fact that the young or short, over-grazed grass tends to be high in potassium and nitrogen. This grass has barely any leaf area available to photosynthesise so is comparatively low in sugars but horses grazing it will still go down with laminitis at any time of the year not just Spring and Autumn.

Horses will also develop Equine Metabolic Syndrome (EMS) on this short grass despite it being low in sugars. (see picture) They will develop the ‘cresty’ neck, fat pads above the tail head, behind shoulders and on the sides of the rump, have swollen sheaths, get puffy and bloodshot eyes, tender-footed and be constantly on the brink of laminitis.

These are the signs you can observe from the ‘outside’, on the ‘inside’ their whole metabolism is in serious trouble. It is a disorder which cannot be corrected by keeping these horses on short, green grass.

In addition, if short, green grass is the only forage available for them to live on it is tantamount to starvation. It is certainly starving the hind-gut flora which need a constant supply of fibre from mature grass/hay. They will not be healthy and will be prone to early onset of age-related diseases. Constant grazing of very short grass also, over the years wears down their incisors to nothing.

Living on short, green grass (as on Jenny Craig paddocks) only makes the condition worse and is a major reason for the epidemic of laminitis here in NZ (and in many other regions of the world). The incidence spikes in Spring and Autumn. Even horses who have never even looked like being a candidate for laminitis can develop the disease on short grass that is very low in sugars (2.2%).

Mid-mature grass, especially when it is ‘lush’ is no better and by now there is plenty of leaf area to make sugars during the sunshine hours. This is the reason, if it is appropriate, to let your horse out for a pick or a graze it is recommended to do so first thing in the morning when the sugars have been used up over-night. Even better is to make sure they have an early morning slice or two of hay BEFORE you let them out rather than letting them out hungry on an empty stomach!

It is very easy to underestimate HOW MUCH grass a horse or pony can consume in just ten minutes let alone a couple of hours. Always best to err on the side of caution. Being a bit slack about this can be a big mistake!

Laminitis is not actually a problem with the horse but a problem with his MANAGEMENT, especially of his grass.