Nutrition 1: Nutrients and Differences Between Dogs and Cats

What considerations do we as veterinary professionals need to consider when examining whether or not a diet is safe and balanced?

1. Nutrient content of diet

2. Energy content of diet

3. Digestibility of diet

4. Species eating diet

5. Palatability of diet

6. Freedom from toxins, micro-organisms

Where does our energy (macronutrients) come from?

Protein

Fat

Carbohydrates

What are the micronutrients?

• Vitamins

• Minerals

Vitamins

• Fat soluble: A, D, E, K

• Water soluble: B, C

Minerals

• Macrominerals: Ca, P, Cl, Mg, K, Na

• Microminerals: Fe, Zn, I, Mn, Cu, Se

What are the essential roles of proteins?

• Required for tissue building, growth and repair

• Production of hormones, enzymes, blood cells etc.

• Protein consists of chains of amino acids

How many amino acids must be supplied in the diet?

• 21 amino acids

• All animals need all of them

• The quality of a protein varies with the number and amount of essential amino acids it contains

What is an essential amino acids?

An essential amino acid is one that the body cannot produce on its own and must be obtained through the diet or supplementation.

How many essential amino acids do cats and dogs need?

• 10 Amino Acids

• Cats need all 10 + Taurine

What amino acids must be provided in cat diets and why?

Taurine

• Cats have limited ability to make taurine from cysteine (similar to man)

• Taurine is an essential amino acid for cats

• It is only found in animal tissue

• It is deficient in cows milk, vegetable based diets, dog food and some homemade diets

• This means that cats are obligate carnivores

What does a taurine deficiency in cats cause?

1. Feline central retinal degeneration (blindness)

2. Feline dilated cardiomyopathy

   1. Very rare to occur in cats

3. Poor reproduction and growth

What is biological value (In regards to protein)?

• What criteria defines a high BV?

• The quality of a protein

• Protein has a high BV if provides essential a.a. in amounts which:

  - closely match animals requirements

  - when most are absorbed and retained (high digestibility)

Summarize the biological value of different animal/plant products.

In relation to dogs, how much protein do cats required?

• What enzymes in their livers allow them to take advantage of protein as an energy source?

• Need 2x as much dietary protein compared to dogs, as they get most of their energy from protein (Whereas dogs/humans get this from carbohydrates + fats)

• Transaminase and deaminase enzymes in liver convert a.a. to glucose to provide energy source

  • Enzymes constantly active

  • If low protein diet, deficiency occurs

What amino acid is needed to help covert aa to glucose for energy, in cats?

• The special pathway in cats for converting glucogenic amino acids to glucose requires serine in large amounts

  • Serine is not an essential aa

  • Found in high quantities in meat, milk and eggs

What amino acid in feline diets is essential for disposing of nitrogenous waste?

• Cats use protein for energy production

• Therefore high levels of nitrogen waste

• Arginine essential in cats for conversion of ammonia to urea

• (of course, it is also essential for dogs)

• Meat is rich in arginine

Why is excessive dietary protein an issue?

• Protein cannot be stored

• Deamination occurs in the liver

• Urea is produced and excreted by the kidneys

• The acid part of the amino-acid is converted to glycogen or fat and stored

Why do we typically lower protein in the diets of older animals?

proteins broken down via kidneys (Older animals may have kidney disease so protein breakdown puts more stress on kidneys), lowering this amount reduces stress on kidney

What are the main structural features of fat?

• Dietary fat consists mainly of triglycerides

• Triglycerides are composed of 1 molecule of glycerol and 3 molecules of fatty acids

• Specific fatty acids determine physical and nutritional characteristics of the fat

What are the main roles of fat in the diet?

• Important as provision of energy, the absorption of fat soluble vitamins, a source of essential fatty acids and palatability!

What are the two essential fatty acids required by dogs?

- alpha linolenic acid

- linoleic acid

What are the essential fatty acids required by cats?

- alpha linolenic acid

- linoleic acid

• AND arachidonic acid, as they cannot synthesise it from linoleic acid, arachidonic acid is only found in animal fat

How can inadequate fat intake affect animals?

• poor growth

• weight loss

• poor reproductive performance

• poor physical performance

• poor skin and coat condition

What are the three main groups of carbohydrates?

• MONOSACCHARIDES : glucose, fructose

• DISACCHARIDES : sucrose, lactose

• POLYSACCHARIDES : starch, glycogen, fibres

What are the main roles of carbohydrates in the diet?

• Energy

• Heat when metabolised

• Storage of energy in form of glycogen or fat

• Bulk in the form of fibre

Is there a minimum requirement for carbohydrates in the diet?

• no minimum

What are some sources of carbohydrates?

wheat, rice, barley, oats and potatoes

Describe the main differences between feline and canine carbohydrate requirements.

• Cats have adequate glucose with low carb and high protein diets

• Cats have few glucokinase enzymes which limits ability to metabolise large amounts of simple carbohydrates

• Must be moderated, low carb. or can get sick

• Again cats strict carnivores, dogs omnivores

What are the key features of fibre?

• Fibre is non-digestible carbohydrate

• Resists enzymatic digestion in SI and is usually fermented by microbes in colon

• Composed of plant materials

• Provides bulk to faeces

• Regulates bowel function (gives gut something to contract against)

• Production of short chain fatty acids

• Therapeutic use in fibre-responsive diseases

How can fibre be classified?

• Fibre can be classified on solubility, fermentability, chemical structure

• Insoluble fibre sources include cellulose, lignin

• Soluble fibre sources include soy, pectin, guar, beet pulp

• Many foodstuffs contain mixed fibre

What are the non-energy producing nutrients?

• Vitamins

• Minerals

• Water

What are the energy producing

• Carbohydrates

• Protein

• Fat

What are some of the main functions of minerals in the body?

‘ash’

• skeletal structure

• fluid balance

• nerve and muscle function

• acid/base balance

• Absorption of different minerals is often linked

What is calcium required for?

• What hormones influence the availability in the body?

• Required for skeletal and dental formation

• Hormones for regulation:

  • Calcitonin (High Ca, decreased Ca absorption from bones and GI tract)

  • PTH and 1,25 dihydroxycholecalciferol (Low Ca, increased absorption of Ca from bones and GI tract)

How might a calcium excess result and what may it cause?

Calcium excess occurs due to:

• supplementation of growth diets

• overfeeding

Calcium excess may result in:

• OCD, hip dysplasia and other skeletal abnormalities

Why is feeding a correct phosphorus to calcium ratio so important?

• Not only is the amount important but the Ca:P ratio is important

• Problems can occur due to feeding high phosphorus/ low calcium diets (such as high meat and offal diets)

• Phosphorus levels should be controlled during growth and in senior lifestage

What conditions may result from excess phosphorus?

• Nutritional secondary hyper-parathyroidism (causes skeletal deformity in growing animals)

• High phosphorous binds Ca, so in an effort to release more Ca, thyroid produces excess PTH, causes bone absorption which leads to deformities

• Renal secondary hyper-parathyroidism (causes worsening renal dx)

• Can occur in kidney disease, as phosphorous is only excreted via kidney

• Renal disease causes hyper-phosphataemia, binds with Ca, causing ionized calcium levels to drop, triggers PTH release, get bone reabsorption

  • This appears as rubber job which affects the mandible

What is the importance of sodium in the body?

• Needed for regulation of body fluid balance

• Excess sodium intake may cause :

• hypertension

• heart and kidney problems

• Excess fluid loss may cause deficiency

• vomiting

• diarrhoea

• Salt also improves palatabilitu

What are some main functions of the following minerals?

• Magnesium

• Iron

• Copper

• Zinc

• Magnesium: component of bone, enzymes and intracellular fluids

• Iron: component of haemoglobin and myoglobin for oxygen carrying

• Copper: for formation of RBC and normal pigmentation of skin and hair

• Zinc: constituent or activator of >200 enzymes

What are the main antioxidant vitamins?

• Vitamin E - intracellular

• Vitamin C - extracellular

What are some species differences between deitary vitamin A in cats versus dogs?

• Dogs can convert beta-carotene into Vit A

• Cats require pre-formed vitamin A

• They lack b-carotene dioxygenase

• This is only found in animal tissues

Why are cats susceptible to vitamin A toxicity?

• Fat soluble vitamin: dietary excess stored, not excreted

• Cats susceptible to vitamin A toxicity

• Fresh liver based diet

• Cod liver oil supplements

• may cause calcification of cartilage eg neck

What are some species differences between dietary vitamin B (Nicotinic acid - Vit. B3) in cats versus dogs?

• Used for hydrogen transfer NAD,NADP

• Small amounts made from tryptophan in man and dogs

• 1% tryptophan converted to nicotinic acid

• Dietary nicotinic acid also required

• None made from tryptophan in cats like dogs and people can

• Nicotinic acid requirement 4x man/dogs

• Niacin or nicotinic acid plentiful in meat and fish

What is notable about vitamin C requirements in cats and dogs?

• Unlike humans and guinea pigs, dogs and cats do not require a dietary source of vitamin C.

• They can synthesise all the vitamin C they need from other dietary components

What function do antioxidants have?

• Combat free radical injury

• Support body's natural defenses, include…

  • Vit E, Vit C, Co, Se

  • Help maintain a healthy immune system

  • Reduce oxidative cellular damage implicated in diseases such as

    • - Cardiovascular disease

      - Obesity

      - Diabetes

      - Brain ageing

What are free radicals and what do they do to cells?

- Unstable oxygen radicals with an unpaired e-

- Highly reactive

- Damage membranes, DNA, Proteins

What are prebiotics?

• Substances used as a food source by bacteria

• Fibre sources such as FOS (fructo-oligosaccharides)

  • Selectively promote growth of beneficial bacteria.......at the expense of pathogenic bacteria

What are probiotics?

• Micro-organisms that when ingested exert beneficial effects beyond that of their nutritional value