Working dogs are truly premier canine athletes.  As such, one should pay close
attention to meeting their energy needs.  There are 3 sources of energy...fats,
carbohydrates and proteins.  Understanding how the working dog utilizes energy
and how best to balance these energy stores can result in a more responsive
partner that is less prone to physical injury.

Fats are the most energy dense of all the sources providing 70-90% of the
energy needed for muscle contraction (primarily fueling slow twitch fibers).  In
the working dog, 50-65% of total energy in a diet should come from fats.  
(This translates to 25-32.5% fat on a dry matter basis.)  When fed a high fat
diet, the working dog will develop pathways that promote aerobic oxidation of
free fatty acids (fat adaptation).  In addition, adding an anti-oxidant such as
Vitamin E and the amino acid l-carnitine can improve the muscle's use of fat.  
Aerobic oxidation of free fatty acids leads to less lactic acid build up in the
muscle and better endurance.

Carbohydrates are stored in muscle as glycogen.  Muscle uses glycogen during the
initial moments of activity and for bursts of speed and power (primarily fueling
fast twitch fibers).  Glycogen stores are relatively small and can be rapidly
depleted leading to muscle weakness and fatigue.  However, diets high in
carbohydrates can lead to de-conditioning (poor endurance, obesity, muscle
injury).  For a working dog, carbohydrates should be limited to 10-15% of the
total energy in the diet.  To improve the working dog's use of carbohydrates,
one should focus on replenishing glycogen stores and slowing glycogen depletion.

Replenishing glycogen stores is accomplished by providing a "good carbohydrate"
at an appropriate time.  Muscle cells have GLUT4 pathways that are active
during exercise and for up to 30 minutes after exercise.  These pathways allow
for the uptake of carbohydrate into the muscle without the release of
insulin.   Simple sugars (glucose, dextrose, fructose, corn syrup) cause an insulin
release that leads to subsequent hypoglycemia (low blood sugar).  Complex
starches (bread, rice, grains) take too long to be digested and absorbed.  Both
cause fluid imbalances that can contribute to diarrhea and dehydration.  
Maltodextrin is a small complex carbohydrate and is the ideal carbohydrate for
this purpose.  Maltodextrin is rapidly absorbed without an insulin release or
fluid imbalance and is readily utilized by the GLUT4 pathway.  When a
maltodextrin supplement is given within 30 minutes of exercise, up to 85% of
pre-exercise glycogen levels are restored.  Without this targeted approach, only
40% of pre-exercise levels are restored.

Slowing depletion of glycogen stores is accomplished in two ways.  First, when
enough fat is fed, slow twitch fibers will use free fatty acids as their energy
source (fat adaptation) sparing glycogen for use by fast twitch fibers.  Second,
supplementing prior to activity with a "good carbohydrate" such as maltodextrin
will give the working dog a little carbohydrate "to burn" before starting on the
glycogen stores.  It is very important to avoid simple sugars and starches to
avoid insulin spikes and fluid imbalances.

Proteins are the building blocks of muscle and should not be a major source of
energy.  Animal source proteins (chicken, beef, lamb, egg, etc.) are preferred
and often offer increased digestibility with a good amino acid balance.  Diets
low in protein have been associated with increased injuries.  A working dog diet
should have a minimum 26% protein.  For hard working dogs, diets containing
30-40% protein are even better.  The goal is to spare the use of protein as an
energy source so it can be used to build muscle mass and repair muscle damage.

In summary, working dogs should be fed a diet high in fat to optimize energy
availability and high in protein to protect against injury.  Carbohydrates should
be supplemented at appropriate times to improve their storage.  Remember,
feed for energy and you will have energetic dogs.

Author's note:  I am frequently asked what and how I feed my dogs.  I feed a quality
performance kibble that is 32% protein and 21% fat.  I add a balanced fat supplement so
that total calories from fat range from 50-55%. Approximately 13-18% calories are from
carbohydrates.  I adjust the total amount fed based on the dog's activity and body
condition.  (Beware, feeding a high energy diet can lead to obesity if one is not monitoring
the dog's body condition on a regular basis.)  I give a maltodextrin supplement after
working.  I give 500mg Vitamin E, 500mg l-carnitine and 400mg glucosamine daily.
Feeding for Energy in the Working Dog
Angie Untisz, DVM
Showdown Kennels