NUTRITION AND FEEDING
The food eaten by different dogs varies considerably yet the majority grow well and remain healthy. This is because dogs, like any other animal, have requirements for specific nutrients rather than particular foods and provided these needs are met, the source {prepared pet foods, fresh raw materials or a mixture} is not particularly relevant. Although the dog is a member of the mammalian order carnivore, in a nutrition sense it is more accurately defines and omnivorous, since it is able to survive on a diet made entirely of materials of animal or vegetable origin. Like the cat it is equipped with strong sharp teeth designed for tearing and cutting meat, but unlike the cat it has adapted a much more flexible and varied diet than one consisting largely of animal tissues. The key to proper feeding is a ‘balanced’ diet ; one which contains appropriate quantities of all essential nutrients, neither to little nor to much. It also embraces other important characteristics of food stuffs often taken for granted-palatability, digestibility, concentration and safety. A food may appear to be suitable on paper because chemical analysis shows that it contains all the essential nutrients in the right proportions, but if it is not palatable enough to be eaten, or if the nutrients are bound in such a way to prevent their digestion and absorption, it is not the balanced diet it appears to be. Similarly the food must be sufficiently concentrated to allow the dog to take in enough to meet its particular nutrient needs, and should be free from any toxins, bacteria or parasites which might harm the dog.
Nutrient requirements
Dogs need proteins, fats, minerals, vitamins and water. They can also utilise carbohydrate although it cannot strictly be described as essential. Most foods contain a mixture of some or all these nutrients and therefore careful combination of different foodstuffs will result in a suitable diet. Nutrients are required in the diet in different quantities. A dog needs 20 times as much protein as calcium and 100,000 times as much protein as riboflavin {vitamin B2}. Even so, if any essential nutrient is missing or present in insufficient quantity, the whole diet will be inadequate.
ENERGY
In addition to providing specific nutrients, food also provides energy or calories . energy is needed not just for muscular activity or exercise, but also for maintenance of body temperature and for processes necessary for life such as breathing and heart function. Even a sleeping dog uses energy. There are many factors which affect energy requirements. Puppy growth, pregnancy and lactation increase the requirements, but for normal adult dogs the most important factor is body weight. The energy requirements of every dog will change through its lifetime. The energy in food comes from protein, fat and carbohydrate which are oxidised, or burned, in working tissues to release energy. each gram of protein and carbohydrate provides about 4 kcal while fat supplies double that amount. Inadequate energy intake will result in poor growth {in puppies} and weight loss { in adult dogs}. It is therefore, important to provide the correct number of calories for the particular dog at the specific stages in its life cycle, taking into consideration its life style and the environment in which it lives.
PROTEIN
Proteins are very long molecules made up of chains of many small units called amino acids – rather like strings of beads. There are 22 different amino acids, but since each combination produces a protein with specific characteristics, there is an almost infinite variety of proteins. Proteins are essential constituents of the cells which make up the body tissues, having several important functions in the regulation of metabolism {as enzymes and some hormones}; in a structural role in cell walls and muscle fibre, in transport of essential materials, and in the body ‘s defence against disease. The protein requirements of growing puppies and pregnant and lactating bitches are greater, weight for weight, than normal adult dogs. This is because protein is necessary for the synthesis of new tissue, and for the production of milk. However even adult dogs need to replace protein broken down and lost from the body every day, mostly in the urine but also in faeces and hair growth.
Protein quality is an important consideration in the selection of foodstuffs and is governed by two factors – digestibility and amino acid profile. Digestible protein that part which is absorbed through the gut wall into the body and not lost in the faeces. The digestibility of protein in the dog can vary from as low as 50 % in some cereals up to 95 % for milk and egg protein. The amino acid profile reflects which of the 22 amino acids are present in the protein. This is particularly important as 10 of these are essential to the dog. Essential amino acids cannot be synthesised in sufficient quantities by the body and must, therefore, be provided in the diet. Non essential amino acids are equally necessary, but can be synthesised if sufficient raw materials are present { in the form of excess amounts of other amino acids and non-protein nitrogen } milk and egg contains the greatest proportions of essential amino acid cereals the least. This does not mean, however, that the dog should be fed entirely on meat, milk and egg but that judicious mixing may be necessary if cereals form a large part of the diet. Protein deficiency can result from either insufficient dietary protein or from a shortage of particular amino acids the observable signs are largely non-specific – poor growth or weight loss, loss of appetite, rough and dull coat and increased susceptibility to disease.
FAT
Fat has several roles in nutrition of the dog: it is a very concentrated source of energy, it enhances the palatability of many foods and it serves as a carrier for the fat-soluble vitamins A, D, E, and K its most important function, however, is as a source of the essential fatty acids, particularly linoleum acid, which is used to form part of the cell walls and which are necessary for the synthesis of prostaglandins. Linoleum acid deficiency results in coarse dry coat, thick dandruff, skin lesions and in reproductive failure . dogs with this deficiency usually respond quickly to dietary supplementation with sunflower oil which is a rich source of linoleum acid.
CARBOHYDRATES
It has been assumed for many years that while dogs are good at utilising carbohydrate as an energy source, it is not an essential dietary requirement. This is because dogs are able to synthesise their glucose requirement from dietary fat and protein if these are present in sufficient quantity. However, recent work in the USA has indicated that some pregnant bitches need a dietary source of carbohydrate in order to produce healthy puppies. It is difficult to reconcile this with what we know of the dog’s evolutionary history history, as the prey which formed the diet would contain very little carbohydrate whether this finding is confirmed or not it is largely academic, as the majority of dogs are traditionally fed diets which contain large proportions of carbohydrates as biscuit or meal.
VITAMINS
Although required in very small amounts, vitamins are necessary for normal health and function. A vitamin is an organic compound which plays an essential part in the regulation of various metabolic pathways and is broken down in the process. Vitamins are distinguished from other compounds with similar functions in that the animal is unable to synthesise replacements and must obtain a dietary source. It is usual to describe the different vitamins by the major specific sign of deficiencies. Thus A is popularly associated with sight, since deficiencies lead to an impairment of vision; vitamin E with reproduction; and so on. This is an over-simplification since deficiencies of all the vitamins have signs in common, particularly poor appetite, general loss of condition and poor growth. Vitamins are classified according to their solubility in either water or fat. This apparently arbitrary division has practical nutritional consequences. The water-soluble vitamins are not retained in the body when given in excess and are lost in the urine. Since they are not stored, regular intake is necessary, conversely, the fat soluble vitamin A, D E and K are retained when fed in excess of requirements.
MINERALS
Dogs require about 20 minerals, but some are needed in such small quantities that the absolute requirements have not been established. These trace elements are present in most common foodstuffs and deficiencies are most unlikely. Minerals have three important functions;
As structural components of bones and teeth {calcium, phosphorus and magnesium};
As soluble salts which
control fluid balance { sodium chloride in blood and extra cellular fluid;
potassium, magnesium and phosphorus inside body cells }
In enzymes and other proteins { such as iron in haemoglobin }.
Many are toxic if given in repeat overdoses and indiscriminate supplementation should be avoided
WATER
Water should be considered in conjunction with feeding. A shortage of water leads to illness and even death more quickly than that of any other nutrient and a fresh supply of drinking water is an essential part of a dog’s diet.
Water is necessary for many different functions in the body. It is used as a transport medium { blood }, the rout for elimination of toxic wastes { urine },for heat loss { evaporation } and many other functions. Water balance is controlled within quite narrow limits, and since some water loss from the body is obligatory, daily intake is essential