Maintenance Protein Recommendations for Canines
Reprinted with permission from www.animalhealthcare.ca
The question of how much protein a canine requires has been the subject of controversy over the past several decades. It is generally agreed that the maintenance needs of most mature, non-working, non-breeding canines can be met by giving the animal 18% of the dry matter as good quality protein (animal origin).
In considering how much protein is required to support maintenance, there are a few things to keep in mind:
- The only function of dietary proteins is to provide the body with essential amino acids (those that the animal cannot make).
- The amount of protein required in the diet will depend on how efficiently it provides essential amino acids.
There is always some damage to dietary proteins during processing and, therefore, their use by the animal is also limited. Because of this, additional amounts may be added to the formula. Another factor that influences the amount of protein added to a diet is the 'quality' of the protein. The term 'quality' reflects the degree to which the essential amino acid profile of the source reflects the essential amino acid requirements of the animal. Those that directly mirror the essential amino acid requirements of the canine are said to be of high quality. If a protein source cannot efficiently provide the essential amino acids required to meet the canine's physiological needs, greater amounts will be required.
The maintenance requirement for protein is based on replacing the amino acids naturally lost as a result of the breakdown of tissue proteins. Excess amino acids are not stored in the body but there are certain proteins which serve as reserves to provide amino acids to the animal in times of starvation or stress. These reserves, called labile protein reserves, are important because they are the only way the body can store essential amino acids for a later time when they will be required. Examples of these stores are xanthine oxidase, blood albumin and the mucosa of the gastrointestinal tract. Labile protein reserves should also be included in the protein maintenance requirement.
To measure the amount of protein (measured as nitrogen) required to replace natural loss, animals are placed on protein-free diets (this eliminates the effects of dietary protein on nitrogen that is lost in feces and urine) and the urinary and fecal losses are measured after a period of protein depletion. The amount of nitrogen lost under those conditions is considered to be the minimum amount of nitrogen needed to maintain the animal and thus determine the animal's maintenance needs for protein. In order to translate this into a dietary intake, it is necessary to increase the amount of protein to compensate for dietary protein that is not digested. When the nitrogen intake is equal to the total nitrogen loss, the animal is said to be in balance.
The nitrogen intake required to maintain nitrogen balance in adult canines was found to be 10-12% of the dry matter if there was 100% utilization of the dietary protein. If a 75% efficiency of utilization is assumed (which is typical for most dry dog foods), then an intake of 16% of the dry matter as protein should meet the canine's maintenance requirement. It was found that under laboratory conditions, growth could be supported with as little as 11.4% of the dry matter as protein of very high quality (lactalbumin) and that maintenance could be achieved with intakes of 6-9% of the dry matter. This suggests that maintenance need for protein is about 60% of the intake required for growth. Some studies suggest that very low levels of nitrogen intake would be capable of supporting normal nitrogen balance and, therefore, maintenance in canines. These studies used proteins of very high quality that are not practical for common use. It is important also to remember that nearly all of these studies were done using protein-depleted dogs and the levels reported would maintain tissue levels but would not contribute to tissue protein reserves. These are usually in the form of various enzymes and, most importantly, blood albumin. How efficiently would these reserves be maintained by feeding diets which contain minimal amounts of protein is not known. The size of the protein reserves needed to cope with life's normal demands is largely unexplored in the canine. One experiment suggested that as little as 6.5% of the dry matter as protein would maintain canines in nitrogen balance if there were 100% utilization. However, canines fed diets that contain this level of casein were more vulnerable to toxins than canines given diets that contained 16% of the diet as casein. This suggests that animals under stress require additional protein. If an allowance was made for differences in utilization between casein and the more commonly-used sources of protein in pet foods, such as meats or meat meals (lamb, poultry, chicken, etc.), a reasonable recommendation for maintenance protein intakes would be 18% of the dry matter.
This level of protein intake is not appropriate for a breeding bitch or a dog that is engaged in stressful activities such as shows (the stress of being in a strange environment with strange animals), sled racing, hunting, or guard work. Those animals have greater needs for protein (up to 32% in the case of sled racers) and a maintenance level intake of protein would not be appropriate. An intake level of 18% of the dry matter as protein is for the inactive family pet who will not be breeding or engaging in any more strenuous activity that a morning or evening walk.
Note: This section of the Canada's Guide to Dogs website is intended as a source of information only. It is not intended as a substitute for professional care. Always consult with your Veterinarian about health related matters.