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Cats, Dogs and Carbs
While carbohydrates sometimes get a bad rap, the main role of
carbohydrates in the nutrition of dogs and cats is to provide energy
for the body, especially the brain and the nervous system. While
recognising that there is no agreed minimum level of carbohydrates that
must be included in the diet of dogs or cats,
inclusion of carbohydrates such as starch into pet foods provides
a concentrated source of dietary energy and dietary fibre for dogs and
cats and is beneficial for stool volume, consistency and intestinal
health in dogs.
Carbohydrates are one of the basic food groups (along with fats and
protein) and include sugars, starches and fibre. Carbohydrates are made
of (only) combinations of carbon, hydrogen, and oxygen and are important
sources of energy for the body. The building
blocks of all carbohydrates are simple sugars (monosaccharides) and
they can be classified according to how many sugar units are combined in
Monosaccharides are simple sugars such as glucose and fructose found in
Disaccharides are sugars that are formed by joining any two simple sugars
(see fig 2). For example, table sugar (sucrose) is a disaccharide of
glucose and fructose and occurs naturally in sugar cane and fruits.
Lactose, another disaccharide, consists of a glucose and galactose
molecule and is the main natural sugar in milk and dairy products.
Fig 1 Glucose: an example of a monosaccharides (a simple
Polysaccharides are made from chains of monosaccharide sugars. Ten or
more (sometimes over a thousand) sugar units are joined to form
polysaccharides. An example is starch, the main energy reserve in root
vegetables and cereal grains. Starch is made of long chains of glucose.
Plant foods like cereals, (such as wheat, rice, sorghum), potatoes and
corn are good sources of starch and these can provide an important source
of energy in the diet.
Fig 2 Sugars
There are various polysaccharides in food that are not starch and these
are termed 'dietary fibre'. They include: cellulose, hemicelluloses,
inulin, pectins and gums. Cellulose is the major component of plant cell
walls and consists of several thousand glucose units (see fig 2). One
sub-group of dietary fibre that has been researched over recent years are
'oligosaccharides' such as fructo-oligosaccharides (FOS) found in a
variety of vegetables (such as chicory and some grains) which are
carbohydrates formed of 3 to 9 sugar units. These types of dietary fibre
are often referred to as 'prebiotics', as they encourage the growth of
specific types of 'beneficial' bacteria in the animal's lower gut.
The role of carbohydrate in the diet
When consumed in the food, an enzyme called amylase helps break down
starch into glucose, which is then absorbed from the gut and utilised
throughout the body, providing energy for daily metabolic function and
activities. The amount of energy in a food is measured in kilojoules (kJ)
or calories. The corresponding 'energy-storage' polysaccharide in animals
and humans is called glycogen, which is primarily stored in the liver
1. The primary function of carbohydrates is to
provide energy for the body, (particularly the brain and the nervous
A feature of dietary fibre is that dogs and cats (and humans) cannot
digest it, so it remains in the gut providing bulk and helping to
regulate the passage of the food through the intestines. While dietary
fibre does not directly contribute to the energy absorbed by dogs or
cats, it is important for gut function and health. Some of the
'oligosaccharides' (e.g FOS) types of fibre can be metabolised
(fermented) by gut bacteria to produce compounds which the cells lining
the lower gut can use for energy.
There is only limited research data about fermentable fibre in cats;
however, there is considerable evidence that fermentable dietary fibre is
beneficial for dogs.
Do cats and dogs need energy from dietary carbohydrates?
All animals have a need for energy in their diet. Dogs and cats can
derive the energy from carbohydrates, fat and / or protein as each of
these nutrient groups can provide energy. There is no agreed minimum
level of diet carbohydrates that must be supplied to dogs or cats,
provided sufficient protein and fats are present to meet their energy
needs, so carbohydrate levels can vary significantly between different
foods for cats and dogs.
Processing during manufacture improves the digestibility (ease of
digestion) of starch in pet foods, through both the grinding and the
cooking of the starch. Dry pet foods, which generally have relatively
higher carbohydrate (starch) content, undergo high temperature
extrusion in processing which has been shown to increase the percentage
of rapidly digestible starch in the food. Cooked starch from rice, oats
and corn in dog foods has been shown to be over 90% digestible and
indicates that dogs digest cereals and low- fibre cereal by- products
efficiently. Recent research into the genetics of domesticated dogs has
indicated that novel genetic changes occurred in the ancestors to modern
dogs (compared with wolves) allowing them to thrive on a diet rich in
starch and that this change was a crucial step in the early domestication
of dogs 2.
Cats differ from dogs in regards to their dietary needs and
physiology. Cats depend more on a process called
'gluconeogenesis' to produce glucose from dietary protein (rather than
carbohydrate), for their energy needs, although there is evidence that
cats can effectively utilise glucose from digesting starch in the diet
3. This is reflected in the National Research
Council's 'Nutrient Requirements of Dogs and Cats' publication by the US
National Academy of Sciences which states: "Although no known dietary
carbohydrate requirement exists for the cat, dry commercial diets usually
contain 40 per cent or more carbohydrate and are well
An example of where some pets find certain carbohydrate in the diet to be
a bit problematic is that some pets (like some people) have
only limited ability to tolerate milk due to limited ability to digest
lactose, the naturally occurring milk sugar (a disaccharide).
Some pets have lower levels of the enzyme (lactase)
required to split the lactose into its individual sugars which results in
undigested lactose remaining in the gut retaining increased water content
in the animal's stool, resulting in diarrhoea.
'Grain free' pet foods
Over recent years, there's been an increase in the number, variety and
popularity of 'Grain free' pet foods offered to the pet owning public,
both in Australia and overseas. This reflects and follows trends in
human nutrition where consumers are offered an extensive variety of foods
to meet their nutritional needs and preferences. It is important to note
that 'grain free' does not equate to 'carbohydrate free', as these pet
foods may include carbohydrates derived from root crops (e.g potato,
tapioca, sweet potato) or pulses (e.g lentils, chickpeas) instead of
carbohydrates derived from cereals such as wheat, oats or rice. Pet foods
made and marketed by members of the Pet Food Industry Association of
Australia (PFIAA) list ingredients in descending order (by pre-
processing weight) on the label to comply with the Australian Standard.
Diabetes in cats and dogs
Diabetes Mellitus (DM) is a complex metabolic disease resulting in
elevated blood sugar levels (termed hyperglycemia). It is a
condition that requires a committed effort by veterinarian and client to
successfully manage in dogs and cats 5.
In both dogs and cats, DM involves loss or improper function of
specialised cells in the pancreas (beta cells) resulting in an inability
of the pancreas to produce sufficient insulin (a regulating hormone); or
the presence of another disease process that prevents the body from being
able to control the amount of sugar in the blood (insulin
Risk factors for both dogs and cats include obesity, other diseases (e.g
infections, chronic pancreatitis in dogs), hormonal abnormalities
(Cushing's Disease) or medications (e.g. steroids). Genetics is also a
suspected risk factor, and certain breeds of dogs (Australian
terriers, beagles, Samoyeds, keeshond) and cats (Burmese) are considered
to be more susceptible to developing D.M 5.
Managing dogs and cats with diabetes can be a substantial challenge and
if you believe that your pet is showing signs consistent with diabetes
the PFIAA recommend that you seek veterinary advice (signs can include a
hearty appetite with weight loss rather than weight gain, increased
drinking and urination)6. Management of diabetes can involve insulin
administration and dietary adjustments to regulate energy intake and
resulting blood glucose levels.
This article is for general information only
This information is provided by the PFIAA as general information for
PFIAA members only. It has been prepared in good faith and has used 3rd
party sources which are believed to be informed and authoritative at time
of publication. PFIAA accepts no responsibility for any damages or loss
whatsoever caused or suffered by an individual or corporation taking
decisions, action or inaction as a result of the information contained in
this report. For advice and information concerning treatment and feeding
your individual pet, we recommend that you seek the advice of your