Thursday, June 11, 2009

Pet nutrition in Layman’s terms: Part 1 Nutrients and Protein

Does the food I’m providing meet my pet’s nutritional needs? As our knowledge of the relationship between diet and health continues to advance and as the range of foods available for our pets continues to expand, it’s more important than ever to base feeding choices on good information. This information can come from various sources. For example from “Nutrient Requirements of Dogs and Cats”, a technical report issued by the National Research Council as part of its Animal Nutrition Series. The Food and Drug Administration relies on information in the report to regulate and ensure the safety of pet foods (Or better: is supposed to ensure, as we all know too well, pet food isn’t always safe). Scientists who study the nutritional needs of animals use the Animal Nutrition Series to guide future research. The series is also used by animal owners, caretakers, and veterinarians to develop specialized diets for individual animals.
To provide good information is one of my goals with this blog. At numerous times I have published on this blog comments and articles about pet nutrition in general. The problem is that many of those articles sometimes get very technical and can be confusing to some of us, others again maybe based on opinions or written for a certain purpose, like for example in order to sell a certain type or brand of food. What I have been missing is simple explanations, kind of written in Layman’s terms and understandable for everybody, easy to read and short and quickly getting to the bottom of things. That was until now when recently, while doing my daily research work, I came across a course, which I decided to publish here with slight modifications. The site itself looks to me like it has not been maintained for quite a while, the last time its copyright notice was updated was in 2005 and many parts of the site are no longer accessible or corrupted. We don’t have to worry about the age of the info, nothing has changed about the basics. The Australian pet food manufacturer Advance created the self study course in cooperation with the Waltham Centre for Pet Care and Nutrition. Waltham, since 1965 has contributed to the advancement of global knowledge on nutrition for companion animals and now has over 600 research and development personnel all over the world. They continuously study in detail the nutrition and behavior of companion animals in a non invasive environment. Their studies cover many specialist areas including veterinary medicine, dietetics, biochemistry, animal behavioral science and breeding science. While this initially all sounded too science oriented to me, it turned out they came up with a pretty cool “crash course” and I decided to share what I was able to salvage here on this blog. As a result I hope I will be able to come up with a simple series designed for those of you who want to learn more about pet nutrition. A series suitable for breeders, vet nurses, pet store retailers, animal trainers or any pet owner who simply wants to learn more about feeding their dog or cat. Today let’s get started with Nutrients and Protein.


Our companion animals, just like we pet owners or as a matter of fact any living creature require food in order to grow, stay alive and live healthy. Food can be defined as either solid or liquid. When ingested, food supplies any or all of the following: Energy providing materials used by the body to produce movement, heat or other forms of energy, material for growth, repair or reproduction and substances necessary to initiate or regulate the processes involved in the aforementioned categories.

The components of food, which have these functions are called nutrients. The food ingested is commonly referred to as diet. Nutrients, which are required by an animal and cannot be synthesized in the animal’s body are called essential nutrients and must be provided for the body via dietary sources, i.e. food.

Diets containing no essential nutrients at all or only in insufficient quantity are considered inadequate. Feeding inadequate diets long term can and will most likely result in suboptimal performance or even in disease.

This series will take a closer look at the basic nutrients, their structure and their functions within the animal’s body. Today we are getting started with Protein.

What is protein? Proteins are very large molecules made up of hundreds of simple, single units called amino acids, bound together by peptide bonds. A wide variety of different proteins are found in nature, with each made up of strings of hundreds or thousands of amino acids, like the beads in a necklace. There are only about 20 amino acids typically found in proteins, but these may be arranged in any combination to give an almost infinite variety of proteins, each with its own characteristic properties.
Functions of proteinAll animals need protein in their diet. Proteins are essential components of all living cells where they have several important functions including regulation of metabolism as enzymes and some hormones and a structural role in cell walls and muscle fiber. Protein is continually being lost in feces, hair, skin and sweat, so there is a constant turnover of protein in the body, even in adults. Of course a growing body needs large amounts of protein for building new tissues. Additional protein is required during periods of growth, pregnancy, lactation and for repair of damaged tissue, such as wound healing. Protein is essential for the body's defenses against disease, including the formation of antibodies. Proteins are also a source of energy in the diet. A Cat's and dog's coat is made primarily of protein. Protein is required for the normal growth of hair and epidermal cells, for skin pigmentation and for sebum production. In a dog, this may account for an amazing over one quarter of the daily protein requirement. Essential and non essential amino acidsAmino acids are classified as either essential or non essential. Essential amino acids cannot be synthesized by the body in sufficient amounts and must, therefore, be provided in the diet. Non essential amino acids are equally important as components of body proteins, but they can be synthesized from excesses of certain other dietary amino acids or other sources of dietary nitrogen. The amino acid profile of a protein determines the proportion of essential and non essential amino acids. Animal proteins generally have a more balanced amino acid profile, with a greater proportion of essential amino acids, and better digestibility than plant proteins. As a general rule, the more egg, fish, poultry and meat protein a food contains, the better it meets the animal's needs for amino acids. This does not mean that pets should be fed entirely on meat, milk and eggs, but the diet should be carefully balanced with amino acids if cereals form a large part of the diet.Protein quality

It all comes down to this simple formula: Amino Acid Profile + Digestibility = Protein Quality Not all the nutrients in food can be digested and absorbed, so the amount of protein an animal needs in its diet also depends on how easily it is digested by the animal. Digestibility is a measure of the how efficiently the nutrients in a food are digested and absorbed into the body. The digestibility of proteins varies from 50 to 95%. This means that between 5 and 50% of protein in food remains undigested and is not available to the animal. Plant proteins generally have lower digestibility than animal proteins. The protein in high quality pet foods usually has a digestibility of over 75%. However over processing of prepared pet foods can reduce their digestibility.
The protein cycleWhen foods containing protein are eaten and digested, the amino acid necklace is progressively cut into smaller pieces by specific digestive enzymes in the gut, until eventually the whole structure has been dismantled either into single beads or pairs of beads called peptides. Protein can only be absorbed from the gut into the bloodstream in this simple form. Once absorbed into the bloodstream, most of the beads are taken in by the body's cells and reassembled in a different order to build the protein structures which the body needs e.g. hair protein or muscle tissue. Therefore after a dog digests a meal containing beef protein, the components of the protein are pulled completely apart and rebuilt into new dog proteins, leaving no trace of the original beef protein in the dog's body. The urea cycleExcess protein is not stored in the body. Instead the left over protein is used to produce energy in a system known as the urea cycle. This process creates a waste product called urea, which must be eliminated from the body via the kidneys. Unlike fats and carbohydrates, proteins contain nitrogen molecules, and urea is one of the few safe forms in which nitrogen can be eliminated from the body. Protein deficiencyProtein deficiency can result from either insufficient protein in the diet or from a shortage of particular amino acids. Signs of protein deficiency include poor growth or weight loss, rough and dull hair coat, anorexia, increased susceptibility to disease, muscle wasting and emaciation, oedema and finally death. Deficiency of a single essential amino acid results in anorexia and subsequent negative nitrogen balance. Protein excessDietary protein in excess of the body's requirements is not laid down as muscle but is, instead, converted to fat and stored as adipose tissue or fat. Feeding excess protein is a relatively inefficient and expensive source of energy in the diet. Concluding key points: Protein is an essential component of the body: Tissues and body fluids, hormones, enzymes and anti bodies. The arrangement, sequence and proportion of amino acids in each protein give it unique properties. There are about 20 different types of amino acids, of which 10 are essential, since they cannot be made in sufficient quantity in the body. Protein quality is a function of the protein source and its digestibility. Excess protein is not stored, but broken down to produce energy in the urea cycle. Protein deficiency causes poor growth, lack of appetite, loss of coat condition and impaired immune function.

How does it all relate to our pets?
Dogs cannot survive without protein in their diets. Dietary protein contains 10 specific amino acids that dogs cannot make on their own. Known as essential amino acids, they provide the building blocks for many important biologically active compounds and proteins. In addition, they donate the carbon chains needed to make glucose for energy. High quality proteins have a good balance of all of the essential amino acids. Studies show that dogs can tell when their food lacks a single amino acid and will avoid such a meal. Dogs are known to selectively choose foods that are high in protein. Whether this is simply a matter of taste or a complex response to their biological needs for all 10 essential amino acids is not known. However, dogs can survive on
a vegetarian diet as long as it contains sufficient protein and is supplemented with vitamin D.

As carnivorous animals, cats derive most of their protein from meat, fish, and other animal products. Some animal-based protein is easier to digest than plant based protein and is better suited to the cat’s digestive system. Dietary protein contains 10 specific amino acids that neither cats nor dogs can make on their own. Known as essential amino acids, they provide the building blocks for many important biologically active compounds and proteins. In addition, they provide the carbon chains needed to make glucose for energy. High quality proteins have a good balance of all of the essential amino acids. Deficiencies of single essential amino acids can lead to serious health problems. Arginine, for example, is critical to the removal of ammonia from the body through urine. Without sufficient arginine in the diet, cats may suffer from a toxic buildup of ammonia in the bloodstream. Although not the case for dogs, the amino acid taurine is a dietary essential for cats. Taurine deficiency in cats causes a host of metabolic and clinical problems, including feline central retinal degeneration and blindness, deafness, cardiomyopathy and heart failure, inadequate immune response, poor neonatal growth, reproductive failure, and congenital defects. Found abundantly in many fish, birds, and small rodents, taurine is either absent or present only in trace amounts in plants. Strict vegetarian diets are not appropriate for cats
unless supplemented with nutrients essential for cats that are not found in plants.

Protein requirements for pets:
Are usually expressed in grams. For example, a kitten weighing 1.8 lbs requires 10 grams, an adult cat weighing 9 lbs 12.5 grams and a nursing cat mom weighing 9 lbs having 4 kittens needs 41 grams of protein daily. A 12 lbs puppy, expected to weigh 33 lbs at maturity needs 56 grams, a mature dog weighing 33 lbs needs 25 grams, a pregnant bitch regularly weighing 33 lbs and expecting 6 puppies 69 grams and a 33 lbs nursing mother with 6 puppies needs, yes, 158 grams of protein daily.

Figuring Grams of Essential Nutrients from Pet food labels
Pet food labels generally do not list amounts of essential nutrients in grams. However, all pet food labels must state guarantees for the minimum percentages of crude (referring to the specific method of testing the product, not to the quality of the nutrient itself) protein and crude fat, and the maximum percentages of crude fiber and moisture. To convert these percentages to grams, simply multiply the crude percentages times the weight of your pet’s daily portion. For example, if you feed your cat one 6-oz (170-gram) can of food per day, and the food contains 8% crude protein, the grams of protein would be 0.08 x 170 =13.6 grams.

Note: For weight conversions use these
conversion tools
Advance Pet Foods
Nutrient Requirements of Dogs and Cats, National Academies Press

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