By Dr Clive Dalton
Unfortunately nutrition is not an easy subject, and you can easily get lost in the technical detail.
The important point to remember is that your working dog is an athlete and deserves more than a leg of frozen mutton at the end of the day.
What a dog needs from its feed?
Carbohydrates
These are compounds made up of carbon, hydrogen and oxygen and provide the "energy" part of the diet. They contain such things as sugars and starch. The most complex carbohydrates are broken down in digestion and end up as sugars before final absorption.
Glycogen is carbohydrate stored in the muscle ready for action. Marathon runners have to build this up days before the race so they dont have to wait for digestion to take place before energy can be used. Working dogs as athletes need this in a big way too.
To get the energy out of the carbohydrates the animal needs oxygen from the lungs via the blood stream. This burns up the carbohydrate releasing carbon dioxide and water which is then excreted. Excess carbohydrates are stored in the body as fat.
True carnivores dont need carbohydrates - but dogs need them in a properly balanced diet. Carbohydrates should not exceed 60% of a dogs diet.
Dogs cannot digest large amount of fibre, so cereals should be cooked before feeding or the dog will suffer from diarrhoea. Too much lactose (milk sugar) will also cause scouring so dont add large amounts of dried skim-milk powder to the diet as it is 50% lactose. Fresh milk contains only 5% lactose.
Proteins
Proteins are used for muscle building and come from both animal and plant sources. The building blocks of these proteins are "amino acids". The dog needs 23 amino acids but can synthesise (ie make its own) only 13, so 10 must be supplied in its diet to prevent deficiency diseases.
The "complete" proteins that contain these essential amino acids are found in eggs, milk, soybeans, peanuts, yeast, as well as muscles and glandular organs. So the best way to make sure you have covered all the essential amino acids in a diet is to use both animal and plant proteins in a diet.
Proteins like carbohydrates and fats are made up of carbon, hydrogen and oxygen. But they have one important difference - they contain nitrogen. Proteins are insoluble in water so have to be broken down by enzyme action into amino acids, which are then soluble and easily transported around the body.
Animals can break down protein for energy but this is not a very efficient process. Surplus nitrogen produced in the process is excreted as urea in the urine. To avoid this, make sure dogs are not fed high protein diets over long periods, and there are enough carbohydrates and fats in the diet to balance things up.
A dog should be fed protein daily as it is not stored in the body in large quantities like fat. It should make up from 20 - 25% of the daily diet.
Fats and oils
These are made up of chains of chemicals called "fatty acids". They contain carbon, hydrogen and oxygen just like carbohydrates, but they differ by having a greater proportion of carbon in them. They also contain more than twice as much energy on an equal weight basis.
So nature has designed fat depots to be highly effective energy stores for times of need. You get a lot of energy into a small bulk! Putting fat on is a very efficient process, for example the energy in 4 kg of starch to can be stored as 1kg of fat. Taking fat off is harder, as you only get 2kg of starch energy from 1kg of stored fat. Remember this when trying to slim down an obese dog or to lose weight yourself!
Fat serves as important body insulation, as well as helping to transport fat-soluble vitamins around the body. It also improves the palatability and texture of dog foods. A shortage of fat in a dogs diet can cause an abnormal skin and hair condition and may increase susceptibility to skin infections.
A dog needs a minimum of 5% of fat in the total dry weight of its diet. At least 1% of the fatty acid called "linoleic" is needed for skin health. If you feed the recommended maintenance level of 20% fat, then enough linoleic will be present.
If you boost the fat level to 40% or more this will provide all the dogs energy needs, but youll risk problems with rancidity. This can then impair the utilisation of Vitamin E, cause deficiencies in the B-complex vitamins and generally depress appetite. If the dog doesnt eat, then it stops thriving. So don’t expect top performance from all that fatty mutton - put it down the offal hole and buy a decent balanced feed.
If you feed these high fat diets, then you must readjust the mineral, vitamin and protein levels to keep the diet balanced. You may also have to add an "antioxidant" to preserve nutrient quality and stop the fats going rancid. Avoid these problems by feeding lower fat levels in the diet.
Vitamins
Vitamins are essential to growth and health. They help the body to resist disease and body cells to function properly. We have to consider two types of vitamins - water soluble and fat soluble.
Water soluble vitamins
The B-complex and vitamin C are water soluble. They cannot be stored in the body in large amounts so must be supplied regularly in the diet.
When a dog loses fluids by vomiting or diarrhoea, its vitamins must be replaced.. Overfeeding these water-soluble vitamins does not cause toxicity as excesses are lost in the urine.
Vitamin B1 (thiamine)
· This is very important to dogs.
· Dogs differ genetically in their need for thiamine.
· Metabolic disturbance, exercise and cold housing may increase demand.
· Only small amounts of thiamine are stored in the body.
· Treating meat for hydatids (freezing and boiling) reduces thiamine - it is lost in the thawed water and boiling juices.
· The heat of cooking will destroy thiamin. Commercially prepared dog feeds have extra thiamine added to their diets to compensate for cooking losses.
· If you are cooking your own feed recipe, add some yeast tablets to it.
· Feed a dog supplementary thiamine 2-3 times a week.
· Brewers (not live) yeast and wheat germ are valuable sources.
· Meat and cereals are also good sources.
· A high fat diet contains less thiamine than a high-carbohydrate diet.
· Never feed dogs raw fish as some species contain an enzyme (thiaminase) which will make thiamine unavailable. Nervous symptoms may develop leading to paralysis. Cooked fish is safe as thiaminase is destroyed.
Other vitamin B-complex
· These include riboflavin (Vit B2), niacin pyridoxin (Vit B6), pantothenic acid, biotin, folic acid, and vitamin B12.
· The best supplies are in wheat germ, brewers yeast, liver and the organ and muscle meats.
· Under normal feeding there should be no problems, but egg white and sulpha drugs can make them unavailable.
· "Black tongue" is a defect of the mucous membranes caused by a niacin deficiency.
· Poor blood clotting can be caused by folic acid deficiency.
· Riboflavin shortage can cause slow growth, poor appetite and low fertility.
Vitamin C
· Plenty of this is synthesised by the dog to meet its needs.
Fat-soluble vitamins
These vitamins (A, D, E and K) need fat to be transported and absorbed by the body. So if the fat metabolism of the dog is upset, then a vitamin deficiency may occur.
Get veterinary advice when supplementing fat soluble vitamins as excess builds up and is stored in the body fat and can lead to problems.
· Liver, kidney, muscle fat and fish liver oil are good sources.
· Handle fats with care - the vitamins are lost if the fat goes rancid.
