by
Susan Thorpe-Vargas PhD
Growth
All of the above energy sources are required, in the proper ratio,
to sustain normal growth. Also required are minerals and vitamins.
The dietary intake ratio between these two vital constituents
is quite critical. With the exception of some of the antioxidants,
we suggest you do not supplement, unless you are quite expert,
or under the supervision of a clinician.
By the time the dog has matured, enormous physical changes have
occurred, with the most rapid growth period being the first six
months. With the exception of lactation, no other stage of life
requires quite the nutrient and energy needs as the puppy. It
has been suggested that until the young dog reaches 40% of its
expected adult weight it should consume twice the normal adult
ration.
After it reaches this weight gradually reduce the amount to 1.2
times the maintenance level. This should support optimum muscle
and skeletal development at a rate suitable for the dog's particular
breed. Adjust the amount fed downward for the large and giant
breeds according to your veterinarian's recommendations, and modify
the amount upward for smaller dogs. Care should be taken not to
overfeed the puppy. Nutrition studies have shown that over-nutrition
early in life increases the number of fat cells and significantly
contributes to obesity as an adult.
The nutritional requirement differences among the various biological
stages of life, especially puppyhood, gestation and lactation,
are crucial enough to warrent using dedicated feeds during those
periods. While a one-size-fits-all feed may be adequate to sustain
the dogs minimal nutritional requirements, it is still less than
optimum. Puppy food should be fed for approximately the first
six months.
Minerals
Calcium and Phosphorus. The ratio of calcium to phosphorus is
extremely important. The optimum ratio lies in a range of 1 to
2 parts calcium to one part phosphorus. Upsetting this ratio results
in bone and growth anomalies. Do not supplement! These two minerals
are responsible for the structural rigidity of bones and teeth.
Additionally, calcium is required for blood clotting and nerve
impulse conduction. Phosphorus is involved in almost all metabolic
processes in the body.
Calcium and Magnesium
The balance between calcium and magnesium is essential for nervous
tissue, heart and skeletal muscle functions. Additionally, magnesium
plays a role in modulating sodium and potassium levels and is
inherent in many essential enzyme reactions.
Potassium
Potassium is necessary for growth, nerve impulse transmission,
fluid balance, muscle metabolisim and heart regulation. Prednisone,
a steroid commonly prescribed in veterinary practice, causes both
a loss of potassium and retention of sodium, which in turn may
exacerbate potassium loss. Protein-rich diets require correspondingly
greater amounts of potassium. Naturally occurring potassium deficiencies
are rare because of the many nutritional sources for potassium.
Meat is one good example.
Sodium and Chloride
These two minerals usually are found in the canine diet in the
form of sodium chloride, also known as table salt. They are the
electrolytes of the body's fluids and deficiencies are rare in
normal commercial diets.
Trace Elements: Iron, Copper, Manganese, Zinc, Iodine and Selenium.
These minerals are considered trace elements because, as necessary
as they might be for health, they are needed in small amounts
to maintain a balanced diet. Iron deficiency, the most well-known
problem, results in anemia and reduce oxygen transport. Note that
iron, like the other trace elements, quickly become toxic if ingested
in excessive quantities. Copper is involved in many biological
functions, including iron metabolism. Thus a diet deficient in
copper can result in anemia even though adequate iron is present.
Excess copper can also cause anemia, most likely due to competition
for absorption stes between iron and copper. The role of manganese
is not well understood. However, it is known to activate many
enzyme systems and thus is involved in a wide variety of reactions.
A deficiency of this mineral results in impaired growth, reprodution
and distrupted lipid (fat) metabolism.
Zinc is essential for protein synthesis and certain enzymatic
processes. Zinc requirements are affected by the presence of other
minerals. For example, a high calcium intake may require more
dietary zinc. A zinc deficiency appears as poor growth and skin
and coat problems. Iodine's only known function is in the synthesis
of thyroid hormones that regulate metabolisim. Deficiency results
in goiters and disruption of the thyroid's hormonal production.
Selenium is acutely toxic, paradoxically an excess produces the
same symptoms as a deficiency. This micro-nutrient has a complex
interrelationship with Vitamin E and the sulfur-containing amino
acids methionine and cystine. Selenium is also a component of
the active site of the enzyme glutathione peroxidase, which protects
cells from free radicals that cause damage to cartilage, cell-membranes
and genetic material.