|
Proteins are very complex molecules composed of simpler elements called amino acids.
The amino acids. are, in turn, molecules that contain one or more atoms of nitrogen and can be symbolically represented as "grooved bricks" needed to build almost all animal and plant tissues. They are also part of hormones, enzymes, and many other essential biological products. There are two types of amino acids:
- Essential amino acids: not synthesised by the body;
- Non-essential amino acids: synthesised by the body.
If the food provides sufficient levels of nitrogen, animals are able to synthesise 12 of the 22 amino acids that are known as "non-essential" . The other 10, 11 for cats, must be included in the diet and are called essential or complete proteins.
Each of these amino acids is different from the others, has it own function and is required in different amounts on a daily basis.
 It is not possible to have a deficiency in non-essential amino acids, since the daily requirement is satisfied by the body based on the individual's needs. However, if one or more of the essential amino acids are missing in a diet, a deficiency is created and the body cannot carry out certain functions. Take, for example, the construction of a wall made up of grooved bricks: if just one of these bricks is missing, work cannot continue, even if there is a large number of other bricks.
Animals cannot store the amino acids that they consume in excess when they eat food. So they are used immediately as energy or converted into glycogen (the "sugar" in the liver and muscles) or fats.
Metabolisable protein energy: 3.5 calories/gram
Approximately the same amount provided by starches and sugars
| Classification of amino acids |
| Essential |
Non Essential |
| Arginine |
Alanine |
| Histidine |
Asparagine |
| Isoleucine |
Aspartic Acid |
| Leucine |
Cysteine |
| Lysine |
Glutamic Acid |
| Methionine |
Glutamine |
| Phenylalanine |
Glycine |
| Threonine |
Hydroxiline |
| Tryptophan |
Hydroxiproline |
| ValineValina |
ProlineProlina |
Taurine
(Only for cats. Only a small amount of it
can be synthesised starting with other amino acids) |
Serine |
| Tyrosine |
The five limiting amino acids that are most often found are:
METHIONINE AND CYSTEINE: only the former is limiting, but it is also used to synthesise the latter.
LYSINE: the amount needed increases with the level of protein in the diet.
TRYPTOPHAN: is contributed by meat derivatives, and is found only in small amounts in grains.
ARGININE: is found in small amounts in grains. It is very important in the diet of all carnivores. In fact, an arginine deficiency, especially in cats, causes an increase in hyperammonemia leading to vomiting and nervous disturbances, even after just one meal.
TAURINE: is contained in animal tissues and is only essential in cats. A taurine deficiency can cause disturbances in the functioning of the retina and in the reproductive activities of cats.
|