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O
nce absorbed, these
amino acids are
reconstituted in the cells
of the body to the exact
proteins the animal
requires or, if in excess, are utilised
for energy. There are 22 amino acids
that their bodies require. They can
synthesise 12 of them. The remaining
ones, essential amino acids, must be
ingested. Under certain conditions of
disease and stress other amino acids
can become conditionally essential.
During liver disease, the animals
ability to synthesise amino
acids and proteins may
become severely
diminished.
Proteins are used
in the animal
as structural
components in skin,
hair, muscle and
organs. They are the
major components
of enzymes and some
hormones essential for
maintaining life. Proteins are able
to provide carnivorous animals with
energy. They also form a vital part
of an animal’s immune system. The
by-products of protein metabolism
yield other essential components such
as L-carnitine and glutathione.
The most consistent way of ensuring
an adequate amount of all the essential
amino acids is to ingest adequate
amounts of food sources that
contain them. Dogs and cats, being
carnivorous animals, are well adapted
to digestion of meat sources, which
contain all their essential amino acids.
An alternative way is to supplement
food sources that contain inadequate
amounts of these essential amino
acids. The most well known example
of this is taurine supplementation
to non-meat based cat foods. As a
general rule, the further a diet is from
an animal’s natural diet, the more
areas it will need supplementing
and the more chance there is for
something to be overlooked. This
applies to other essential
nutrients such as
essential fatty acids
as well. Deficiencies,
such as taurine
deficiency, caused
heart failure in many
cats before the
cause was linked to
a dietary deficiency
of this essential amino
acid in this species.
Kittens, puppies and aging
dogs and cats actually have the
highest requirements of essential
amino acids. The best examples of
inadequate essential amino acid and
caloric ingestion can be seen in older
animals, where the shapes of their
bones start to be visible because of
a loss of muscle mass. The body
will utilise its own muscle mass for
essential amino acids if ingestion of
these nutrients is inadequate. This loss
of lean muscle mass is best seen over
the head, spine, shoulder blade and
hip area. Sometimes these animals
even have excess body fat, this is a
condition called sarcopaenic obesity.
The actual protein requirement of
the cat is higher than that of the dog.
This is a result of cats’ greater need
for protein for the maintenance of
normal body tissues and the inability
to down-regulate certain catabolic
enzymes in the liver used to convert
protein to energy, regardless of what
other source of energy are provided
in the food (fat, carbohydrate). The
metabolisable energy of protein in
dogs’ and cats’ diets is 3.5-4 kcal/g,
approximately the same amount
of energy supplied by dietary
carbohydrate. Animals are unable to
store excess amino acids; they are
either used directly for energy or are
converted to glycogen and fat for
storage.
As mentioned earlier, animals also gain
important by-products when proteins
are broken down for energy. Another
example of this is the molecule,
phosphotidyl choline, which protects
an animal’s biliary tract from the
caustic action of its own bile. Bile is
important in food digestion and if the
biliary tract, which is also food, is not
adequately protected, biliary tract
damage will ensue.
The amount of protein that an animal
needs to ingest, in order to obtain
adequate or optimal amounts of
essential amino acids and energy,
Why do
dogs and cats
need protein?
The truth is that dogs and cats do not need any protein in
a healthy state at all. What they do need is the building
blocks of proteins. Even if animals ingested their
exact daily requirements of protein in their diet, their
alimentary tract would still break the proteins down to
individual amino acids through the process of digestion.
Dr Martin de Scally
Article
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