Written By Dr. Kris Hiney
Last month we discussed the function of electrolytes and some special disorders of horses related to these minerals. This month we will look at how much of these minerals your feed usually supplies, and determine how much electrolytes you may need to try and supplement to your horse.
How much do they need?Overall, the diet of the horse should contain between 0.25-0.5% salt. So, for example, let’s assume we have a 500 kg horse that eats 2% of his body weight per day. In total, he would consume 10 kg of feed per day. If we use those ranges of intake listed above, he should be ingesting between 25 and 50 g of salt per day. Therefore, the minimum a maintenance horse should be ingesting is about 25 g of salt per day. This will provide sufficient sodium and chloride for the horse. If we look at some typical hays for horses, the sodium content is quite low. Let’s just pick one and do the math to see how it works out. If we use the generic cool season grass hay, feeding 10 kg of this hay per day would supply 8 grams of sodium, 213 g of K, and 92 g of Cl.
Table 1. Average values on a percent basis for sodium, potassium and chloride for four general types of hays.
|Types of Hays
|Cool season grass (mid maturity)
Table 2. Sodium, chloride and potassium requirements for different exercise classes of a 500 kg horse in grams/d.
Comparing this to the maintenance horses requirements listed in table 2, tells us that the horse really needs to only get extra sodium. In fact, only the heavily exercising horses will probably need additional chloride supplied to them. Again, this is heavily dependent on the temperature in which the horse is working.
What about grain?
Many horses also receive a concentrate in addition to the forage they are eating. Typically, most horse feeds are formulated to contain between 0.5 and1% salt. This increased concentration of salt in the feed is based on the knowledge that most horses will be consuming less grain then hay. Let’s use our same horse above, and now feed him a diet that adds 5 lbs of grain per day. (Wondering how much hay and grain your horse should be eating? See Rules to Feed By)
I’ll convert back to kg so that we can look at our numbers on a gram basis. 5 lbs of grain is equivalent to 2.2 kg. If we assume our grain has 0.5% salt in it, then it supplies 11 g of salt. That breaks down to about 4 g of Na and 7 g of Cl (salt is 39.3% Na). Therefore, your concentrate may be helping to meet your horse’s salt needs. However, the tricky part is that the salt concentration is typically not listed on the feed tag, so you really don’t know how much it is supplying (See Using Feed Tags
). Therefore, to be safe, you should supply your horse with some sort of salt source in addition to his feed. If you look at most feeding guidelines for equine feeds this is why it is stated to also supply your horse with salt on a daily basis. Take for example Omega GRANDE. A one day serving for horses is 227 grams. For the horse to consume it’s minimum amount of salt, Omega GRANDE would have to be 11% salt if it was to serve as the sole salt provider! And that would be just for a maintenance horse. Horse will not consume feeds with high concentrations of salt, and salt addition can even be used in some livestock species to limit feed intake. Consider that many horses really don’t need to be eating grain to begin with, or at least a reduced amount to avoid obesity, supplementing salt is always a necessity.
Since we know that typically feeds alone won’t meet our horse’s needs, (or we may not really know what they are supplying), the easiest way to meet the horse’s needs is to supply a salt block. Researchers have shown that on average horses willingly consume about 50 g from a salt block per day. However, the variability in intake is high. Individual horses may range between 9- 143 g of salt per day! Therefore, some horses will eat too much, while others not enough. Even the same horse may alter his intake of salt quite a bit from day to day. If you really like projects, and have a sensitive scale at home, you could determine your horse’s average salt intake per day (if he is kept alone with his block) by weighing it every day. Also, some horses just won’t eat their block. If your salt block shows no evidence of licking and is covered with dust, you have a non-licker. Alternatively, you could try to provide loose salt, which some horses prefer or specifically feed salt to your horse. So how much salt should you provide your horse per day, especially if he is a non-salt block licker? For your maintenance horse, that would be about 1 oz. which is 28 grams. If you prefer to use your teaspoons to measure instead, one teaspoon contains 6 g of salt. So your horse would need 4 teaspoons of salt per day.
A horse in heavy work requires about twice the maintenance amount, or about 50 grams of salt per day. However, for those intensely working in hot climates, some researchers have indicated their need for electrolytes may increase 9 fold. Now remember, these are probably the race horses, three day eventers etc. Obviously for the exercising horse in hot climates, they may not be able or willing to consume that much via their salt block, which is why it is important to look consider supplementing your horse. Now remember, these horses would probably be consuming more grain than our example horse above, due to the increased energy demands placed on them. Therefore, you may presume that they are taking in much more salt in the diet. If you are supplementing your horse with table salt, you would increase that amount from maintenance to 2 oz or 8 teaspoons (2 2/3 tablespoons), with an increase to 3 oz or 12 teaspoons (4 T.) in hot climates. There are also many commercially available electrolytes as well which can be added to water or provided in a paste form.
Getting the water back inTypically if you need to provide a horse with electrolytes, you should also be concerned with rehydrating the horse. Oddly enough, the horse’s own system can work against it. As the sweat of horses is so much more hypertonic (or contains more solutes) than its plasma, when horses sweat heavily, their blood becomes hypotonic. It does not provide the normal stimulus to drink that having a higher electrolyte concentration in the blood does. Therefore, even if offered water, your horse may not drink. Providing electrolyte pastes or saline solutions after exercise may cause the horse to restore his water balance and recover more quickly. However, do not just offer a horse a salt water solution if they have not been trained to drink it. This will result in water refusal and only exacerbate the problem. They should also be offered a choice of non-saline water to ensure that they replenish the water they have lost. In addition, horses seem to prefer tepid water to ice water when given a choice. So remember, it is as imperative that the horse is also restoring his water balance after exercise as it is to provide electrolytes.Next month we will look at two very important trace minerals, copper and zinc.