Endurance Riding, Part 3, Section 3

Exercise, Feeding and Energy Sources

By Kristene Smuts

Different Sources of Energy

There are two primary energy sources within the horse's body - fat and glucose. Fat is a "cool" energy, meaning that it doesn't produce a high level of heat to metabolise, but glucose on the other hand is a "hot" energy, producing a high level of heat to metabolise. Also, fat is a long lasting energy source, taking a long time to metabolise, where glucose is an immediate energy source. The body stores fat very economically (as we ladies can testify) but the storage of glycogen is much more inefficient, needing more space for the same amount of calories. It has been calculated that the horse's body can store approximately 153 000 calories in the form of fat as opposed to a mere 18 000 calories in the form of glucose.

Fat does have a disadvantage in that it needs glucose to activate the conversion process as well as needing the presence of oxygen. In contrast, glucose doesn't need oxygen to metabolise and when your horse goes into anaerobic exercise levels, glucose is utilised for energy production being a quick and immediate energy source. The depletion of glucose levels results in lactic acid forming.

The horse's body is very clever in that it knows when to use which energy source. When the exercise level is such that enough oxygen is being circulated through the body - aerobic exercise - fat will be utilised as the primary energy source. As soon as the body goes into an anaerobic state, glucose will be utilised. Your ride strategy should take this into account when you ask for different exertion levels.

To summarise : Keep hydration levels high by feeding roughage; don't feed a heavy meal within about 3 hours of exercise; don't push your horse beyond his limit; keep exertion levels within the aerobic threshold; learn which exercise levels use which energy sources.

Feeding Strategy

Now we get to the feeding strategy and which foods provide which energy sources.

Protein - lucerne, soya beans, linseed. A performance horse generally needs 8-10% protein in his diet. For a horse ridden for an hour to two on a weekend, these requirements are met by good quality hay and grazing - no need to supplement unless he's a hard keeper and you're trying to maintain body condition.

Metabolically, protein is very expensive as nitrogen is a by-product of protein conversion. Nitrogen has been named partly as a cause to azoturia or tying-up syndrome. Arab horses and those with a high percentage of Arab blood as well as the various draught horses, are very prone to azoturia, so the protein content in feed for these horses should be managed more so than with the other breeds. (You were hoping to find something wrong with Arabs, weren't you?).

By feeding more protein means that more nitrogen will be produced. Nitrogen is converted to ammonia and then to urea which are toxic substances in the body. The excretion of these substances take precedence over water conservation within the body and are excreted via urination. A high percentage of nitrogen in the body will cause the horse to urinate more - this is not what you need in your endurance horse when you're trying to keep him hydrated!

The conversion of protein in the body produces 3-6 times more heat than the same amount of carbohydrate or fat. This heat is dissipated via sweat and respiration, so if your horse is already sweating to cool down during normal exercise, this extra heat load will cause greater sweating, unnecessarily depleting your horse of precious fluid. So now you have a horse that's urinating more on top of sweating excessively due to extra protein in the body - not good!

Carbohydrate - stem and leaves of grass, hay, lucerne, grain (seeds on grass). Carbohydrates are converted in the small intestine to glucose which is stored as glycogen in the horse's muscles and liver. As can be seen from the foregoing, glucose is the immediate source of energy when required to work in an anaerobic state.

Fat - vegetable oil, full fat soya. A minimal amount of fat is derived from carbohydrates which means that if you're wanting to build up a decent stash of fat in the body, you'll need to supplement fat in the feed. A good source of fat is normal vegetable oil (sunflower, canola), but remember that if you buy in bulk, it can go rancid in our summer heat. Rather buy in 5 litre quantities. Feeding the azoturia-prone horse on a high fat diet, has been widely accepted as a good practice.

Start off with about 1/3 cup of oil per feed, increasing it slowly to 1 cup per feed over a period of about 2 weeks, getting your horse accustomed to the taste. The jury is still out on whether you should feed fat for a number of weeks before the ride only, or whether you can feed it right throughout the year. I personally never stopped feeding fat during winter, helping to keep that layer of fat on my horse's body to help with the chill. He hasn't shown any negative effects, so my personal feeling is that I'll keeping doing it until told otherwise.

Right, now that I've totally confused you, here is a summary about feeding your endurance horse : concentrates should not contain more than 10% protein; feed roughage for good hydration; add fat to the diet for better energy usage and managing azoturia.

Conversion Tables

To make your life easier when reading about gallons and miles! (Rounded for ease of calculation)

InchesMillimetres 10mm = 1cmMilesKilometresFeetMetres 1000m = 1kmOuncesGrams

The figures printed in bold (1 to 5) in the centre column can be read as either metric or imperial, thus 1 inch = 25.4 millimetres or 1 millimetre = 0.04 inches.

It's not so easy to convert Fahrenheit to Celsius and vice versa, but there is a formula you can use :

0 deg C = 32 deg F - water freezes
100 deg C = 212 deg F - water boils at sea level

F (Fahrenheit) = C (Celsius) x 9/5 + 32 (deg F)
to calculate what the Fahrenheit is if the temperature is 35 deg C : 35 x 9/5 = 63 + 32 = 95 deg F

C (Celsius) = F (Fahrenheit) -32 (deg F) x 5/9
to calculate what the Celsius is if the temperature is 80 deg F : 80 -32 = 48 x 5/9 = 27 deg C

Part 3, Section 4