Max Athletic Performance

Why Fat-Enhanced, Lower Starch Diets

Help Maximize Athletic Performance

Dr. Daniel J. Burke, Ph.D., Director of Tribute Equine Nutrition at Kalmbach Feeds

FITNESS

A horse becomes more fit due to physical and biochemical changes in his muscle and cardiovascular system elicited by exercise over time (training). We will discuss some of these changes and how the horse’s diet can maximize the benefits of the biochemical responses to exercise.

TYPES OF EXERCISE :

There are two main types of exercise, with a great range in between. The first is MAXIMAL EXERCISE – work of high-intensity for a short period of time (seconds), such as sprint racing. The main substrate used to supply energy in maximal exercise is carbohydrate (CHO), though fat and protein can be involved depending upon the fitness of the horse and the diet he is being fed.

The second type of exercise is SUBMAXIMAL EXERCISE – work of low-intensity for a long period of time, such as endurance racing. In a fit horse, the major energy substrate is fat.

Obviously, there a many types of exercise that fit between maximal and submaximal, like dressage and jumping, as well as longer races (minutes). The preferred energy substrate would depend on how close to maximal or submaximal the work is and the fitness level of the horse.

It is important to note that CHO and protein are metabolized ANAEROBICALLY (without oxygen), with the main end-product being LACTIC ACID, a primary cause of fatigue. Fats, on the other hand, are metabolized AEROBICALLY (with oxygen), with the end-products being CARBON DIOXIDE (CO₂)and WATER. The end-products of fat metabolism, are much less disturbing to acid/base balance of the horse and will delay fatigue. Horses will only use protein as an energy source when the diet contains more protein than will meet the horse’s requirement. Using protein as an energy source is not only wasteful, but has been shown to decrease the horse’s performance.

The energy substrate preference changes as the horse becomes more fit. In a fit horse, a greater portion of the exercise bout utilizes fat, sparing CHO for the times in a race when maximal effort is required – starts and finishes.

LONG-TERM PHYSIOLOGICAL RESPONSE TO EXERCISE:

Over many weeks of training, important changes in physical and biochemical characteristics of the horse develop.

Improved oxygen (O2) carrying capacity - better delivery of O2 to working muscles, supporting use of fat for fuel.
Muscles use O2 more efficiently.
Reduced lactic acid production - delays fatigue.
Horse can tolerate higher levels of lactic acid before fatigue sets in.
Increased fat utilization, sparing glucose.
Increased resting glycogen concentration - more fuel for starts and finishes.

What does this mean in practice??

The natural response to training shifts the preferred energy source from carbohydrate to fat.
A higher portion of the workout/race is run on fat.
Increased glycogen stores in muscle - more energy for starts/finishes.
Increased time to production of lactic acid - delays fatigue.
Increased tolerance of lactic acid - delays fatigue.

How can I take advantage of the training effects in my horse’s diet?

Over 30 years of work has been done on exercise and the advantages of feeding of fat in horses. In general:

Each unit of fat contains over twice as much energy as the same unit of carbohydrate, with NO lactic acid production.
Fats are well digested by the horse; most sources are 75% to 95% digestible.
Energy from vegetable sources (soy, corn, flax) is utilized 30% more efficiently than CHO energy derived from grain and hay.

Research has demonstrated the following benefits of feeding high-fat diets:

Increased endurance (the ability to sustain speed over longer periods)
Horse operates at lower body temperature during exercise – delays fatigue.
Decreased respiratory effort during exercise – delays fatigue.
Can meet energy needs with less feed – carry less gut fill to the arena or race track!! Higher fat diets can meet a horse’s nutritional needs with 75 – 80% of the amounts required by traditional feeds. Can translate to 8 – 12 pounds LESS gut fill over a 3-day period (concentrations other nutrients must be adjusted for lower intake of feed to meet requirements).
Increased lactic acid threshold (time to rapid increase in lactic acid concentration in the blood during exercise) – delays fatigue.
Increased free fatty acids in blood – supporting other benefits of higher fat diets.
Sparing of muscle glycogen stores during exercise – more energy for start and finish.
Increase in resting muscle glycogen store – more energy for start and finish.
Fat also helps to reduce shifts in blood insulin levels, which occur after a high CHO meal. High insulin levels are detrimental to performance and cause fractious behavior, as discussed below.

High levels of grain and molasses: Negative Effects of High Sugar/Starch Diets

The main effects were are trying to reduce by minimizing the soluble CHO (sugar and starch) content of the equine athlete’s diet are lactic acid production (already discussed), as well as the insulin increase caused by increased blood glucose levels due to high soluble CHO diets.

The effects of high blood insulin levels due to sugar/starch digestion in the foregut are:

increased movement of glucose and amino acids into cells. This action may correlate to a horse tying-up.
increased glycolysis. This may also correlate to tying-up by increasing lactic acid production.
may affect serotonin levels in brain. May explain hyperactivity and behavioral problems in some horses on high CHO diets.
has been associated with ulcers – due to fermentation in foregut.

Research has suggested diets greater than 30% soluble CHO will bypass the small intestine and pass to the hindgut, where they will be fermented by the microbes. Many high grain/high molasses feeds, though typically inexpensive, can be 60% or greater in sugar/starch!!!!!!!

The digestion of sugar/starch digestion in the hindgut favors lactic acid production, which is poorly absorbed and results in a reduction of pH in the hindgut. Acidic pH is correlated to:

1. osmotic diarrhea (water shifts in to large intestine).

2. overgrowth of pathogenic (disease causing) bacteria.

3. destruction of beneficial bacteria – related to colic, endotoxemia and laminitis.

SUMMARY - How do we manage nutrition for the equine athlete??

Supply up to 15-20% of needed calories with fat during training and events.
Decrease starch in diet (less corn, molasses, etc.).
Increase digestible fiber in diet (excellent quality grass hay, dried beet pulp).
Control feed intake - feed more often during the day; make good grass hay available at all times.
Use professionally designed diet to ensure balance of all nutrients with lower intake of higher fat feeds.
Supply electrolytes when horse is sweating.