How the Seasons can affect some Horses



Have you ever noticed at certain times of the year your horse's behaviour can vary or they have been ill? For horses grazing on grass, the changes in the seasons mean quite big changes in the grass and living conditions. Here are a few explanations and tips that can help you overcome some of these issues.




Horses over autumn can really struggle at this time of year, which brings some of the biggest changes in the grasses. Quite often horses behaviour will become erratic, spooking at things more often and more agitated in general. Some horses may become very stiff and short stepping and sometimes immediately after rain you will notice them very tender footed. Seasonal head flicking horses will quite often start in autumn and it is not unusual for horses to colic after rain in autumn.


This season just past for most parts of Australia was quite green over summer so we did not see as clear a change between the seasons as in past years. But the changes still occurred never the less.


During autumn the grass growth surges before slowing right down or in some grass species going dormant over winter. You will notice areas that previously were dirt or very close cropped grass will overnight shoot up delicate green shoots. One way of describing it is it looks like a bright fluorescent green carpet. This grass is minerally very out of balance, containing low sodium, very high potassium and nitrates. In some grasses such as Kikuyu they can even contain high levels of toxins which can cause colic.


A common mistake that horse owners make is they see all these green shoots of grass and think there is enough feed for their horse in the paddock and stop feeding out hay. This forces the horse to eat grass they may not normally eat or larger amounts of this grass which can cause mineral imbalances and in some cases to be toxin/myco-toxin affected as well. It is through these mineral imbalances and high toxins/myco-toxins that the horse can then develop neurological problems and muscle pain. The high levels of potassium and nitrates can strip vital nutrients such as magnesium, calcium and sodium (salt) out of the horse's system causing imbalances.


Over autumn when the grass is so out of balance it is advisable to increase your horse's intake of magnesium, calcium, sodium and to feed a toxin binder twice a day. Highly absorbable forms of magnesium and calcium with co-factors will give you the best results. For more information and specific dose rates please contact Gotha Equine.


With such high rainfall this year the amount of Clover (native and introduced) has increased from past years. There has been a large number of horses exhibiting photosensitivity (looks like mud fever) which can be quite distressing for both the horse and owner. If you can reduce the amount of Clover that they have access to and reduce all Lucerne in their diet this would decrease the amount of photosensitising elements in the horse's ration. Lucerne contains the same photosensitivity producing elements as Clover. Of course if there is lots of mud that they are standing in this will cause mud fever, and giving them a dry hard stand to be able to get out of the mud can be very useful.


When horses get photosensitivity or mud fever quite often they will get a secondary skin infection. I've found smearing Vaseline on the skin the night before washing it with diluted Imaverol (available from your produce store or vet) works very well at clearing this up. The Vaseline will soften the scabs so they easily come off when very gently sponged with the warm diluted solution of Imaverol. If your horse has white or sensitive skin or has been infected for a long period of time, I suggest you halve the suggested dilution rate, to be on the safe side for the first 1-2 washes. Follow the instructions and never use Imaverol without diluting and take care to not scrub the area to further inflame the skin as this can lead to swelling.


Myco-toxins in the pasture environment can increase quite dramatically over autumn. Conditions are ideal for myco-toxin producing fungus. You will notice quite a lot of mushrooms and toadstools in autumn. They are not producing the myco-toxins but they are a good indicator of ideal conditions for fungus. The roman word "Myco" means fungus and toxin is of course toxic, dangerous to ingest. A toxin binder at the full dose rate split over two feeds a day can help with myco-toxins at this time of year. Toxin binders should not be considered a cure and if your horse becomes ill or shows severe signs such as staggers they need to be moved to safer pastures or removed from the grass.




Over winter the grass growth slows considerably and some grass will be dormant, so the levels of potassium and nitrates will not be as high. Horses that react to the spikes of potassium and nitrates will be much healthier and happier. Quite often over the winter months owners turn their horses out and stop feeding them a hard feed with their much needed vitamins and minerals, thinking that if they are not being worked then they won't need them. This can be an easy trap to fall into. The problem with this is horses burn quite large amounts of magnesium over the colder months and while it is good that the grass has dropped in potassium and nitrates, other nutrients will have dropped as well such as calcium and magnesium. If you stop supplementing over winter they will then have to rely on the stores of calcium and magnesium in their body.


The problem with this is they may not have had enough of these major minerals to start with and with a long, cold winter you could find the depletion creating problems just in time for the spring flush. Magnesium, calcium and sodium are used to neutralise excess potassium in the body. If their levels are low this can cause a massive mineral imbalance. To help avoid massive mineral imbalances, keeping your horse warm and dry over winter will help, plus ensuring they still get their much needed vitamins and minerals. A high fibre ration using horse safe hay if available, will benefit your horse and his overall health and help keep him warm over.


During the wetter months it is helpful to know that horse worms are much more active as the larvae and eggs need moisture to survive. It is important to be diligent with your worming program to reduce the risk of damage from intestinal worms. Contact us for a free de-worming program. Some of you may notice that your horse's manure goes quite dry over the winter months. This is quite likely due to them not drinking enough water. You will know yourself that you're not as likely to drink as much water over the cooler months. To help trigger the drinking reflex in horses it is a good idea to make sure they are getting fine salt (non-iodised) added to their feed every day along with their vitamin and mineral supplements. Salt, calcium and magnesium are three elements that need adjusting according to the horse's situation. Whether it is the time of year, their work load, lactating, growing or on oxalate grasses.


Watch out for short Rye Grass over winter as quite often horses will be left in a paddock until the grass is quite short which is not ideal. The toxic endophytes in perennial Rye Grass stay in the lower leaves and in spring when it seeds, travel up the seed stem into the seed heads. So over winter if you do not manage your pastures correctly your horses could be eating toxic endophytes which can cause a whole list of problems ranging from affecting the horse's nervous system to suppressing their immune system. So in effect you could have a horse that is not only mineral imbalanced by the end of winter, they will also have a compromised immune system.


A toxin binder can be very helpful but should not be considered a cure. You are much better off managing your pastures to keep their myco-toxin intake to a minimum. If you do not have any choice and must graze your horses on some Rye Grass, avoid letting the grass get short and only graze them on the mid growth of the plant. The good news is that the myco-toxins in the general environment reduce over the colder months so if your horses are not grazing any Rye Grass you can reduce or stop feeding the toxin binder while it is cold.




With the increase in rain and air temperatures during spring the grass can have huge growing spikes. With this comes very high spikes in potassium and nitrates. If you have ever had a horse go dead lame overnight in the hind end during spring it is possible your horse was suffering from grass tetany. Magnesium, calcium and sodium can be stripped out of their system quickly to eliminate the extremely high potassium, that there is not enough left for their muscles to keep functioning normally. Note that they can have mild symptoms of tetany such as stepping short or appear sore behind when the grass potassium levels are high, in rapidly growing grass. This is one of the reasons it is so important to ensure that your horse is getting their total seasonally adjusted dietary intake of sodium, magnesium and calcium to ensure that the stored and circulating levels in the body are kept at optimum levels. During work your horse is using up vital vitamins and minerals and they must be restored.


With moisture and warmth also comes fungus/moulds so the myco-toxins produced by these will increase. Feeding the full dose rate of a toxin binder split over two feeds is advisable during this time. Rye Grass will become more dominant in the pasture and go to seed over spring and early summer which can cause a long list of issues with horses, including Rye Grass staggers.


When the grass growth spikes so does the grass sugars (fructans) and the danger of horses becoming overweight. If a horse or human for that matter stays overweight for too long, type 2 diabetes (insulin resistance (IR)) can be triggered. IR can be very debilitating for a horse and can be fatal so it is important to manage your horse's weight to avoid IR. Typical signs that your horse is getting too fat and is at risk of triggering IR is a cresty neck, fat pads about the tail and shoulders and generally looking obese. Restricting the time they have on the grass each day or using a grazing muzzle can be a way of avoiding overweight horses.




Early summer conditions are very similar to spring conditions, and with the increase of warmth brings the further increase in grass growth and spikes in potassium and nitrates which I have already mentioned. Once the rain subsides and the heat continues the grass then proceeds to dry off. The only exception to that rule I have found is Paspalum Grass can remain green when all other grasses have browned off. The problem with that is horses then seek out the only remaining green grass which will have higher sugar levels being more palatable. Paspalum under certain conditions can be quite toxic to horses and cause Paspalum staggers. If this occurs they must be removed from pasture containing Paspalum.


You will notice over the dry summer periods that horses can be much more settled and relaxed, except of course, if you are feeding a high potassium diet which could duplicate the same issues that horses on spring grass have in regards to behaviour and movement. For a copy of a low potassium and low sugar diet for your horse please contact Gotha Equine. It is important to always have clean drinking water available for horses but this is worth extra attention over the summer period as horses can drink quite large volumes of water on hot days.


In summary, to help your horse cope with the high spikes of potassium and nitrates you can help them by ensuring that their intake of calcium, magnesium and sodium are at optimum levels all year round. To assist with the absorption of these elements their co-factors should also be present. Magnesium, calcium and sodium are generally not supplemented in many vitamin and mineral mixes to the levels needed to combat the very high spikes of potassium and nitrates in grasses. Ideally you should be able to increase and decrease calcium, magnesium and sodium as the seasons change, the same goes for a toxin binder. In addition a multi-vitamin and mineral mix is advisable to ensure they are getting all the other vitamins and minerals they need plus helping with the absorption of their much needed calcium and magnesium.


Familiarise yourself with the grass and weed species in your horse's paddock and understand that short stressed grass can contribute to stressed horses. Managing their pasture and their weight will help you avoid many issues that can arise. Horses, unlike cows, do not need high powered grass to do well on. Ideally they need slower growing species of grass that is mature, mineraly balanced and low in sugar.


For further information, please contact Lucy Prior of Gotcha Equine.


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