Fishmeal is an excellent source of calcium and phosphorus for poultry. The ash (mineral) content of fishmeal can range from 10 to 25%. The higher ash content is usually an indication of a higher calcium and phosphorus level. The calcium and phosphorus are in a highly available form, unlike some of the calcium and phosphorus in plant proteins. One of the only minerals in fishmeal that is not readily available to poultry is the trace mineral selenium. The selenium in fishmeal exists in the form of selenoproteins which are not considered to provide readily available selenium to the bird
Fishmeal is a high protein feedstuff often included in poultry diets. It is usually marketed at 65% crude protein, but the crude protein content can vary from 57 to 77%, depending on the species of fish used. Several species of fish can be processed into fishmeal, but the most common is Menhaden. Menhaden accounts for about 90% of U.S. fishmeal production.
Most fish species can not be harvested year-round. As a result, there is seasonal variation in protein content, depending on the species of fish used. The crude protein content of fishmeal is usually highest during the Menhaden harvest. During the month of May, the protein content increases as the Menhaden harvest begins. When lower protein species are harvested at other times of the year, the protein content decreases.
The price of fishmeal varies throughout the year and is a reflection of the seasonal variation in the supply of fish. The price of fishmeal is usually the highest during the winter months when the supply is lowest. The price also varies from year to year depending on the price of other protein sources, in particular soybean and other oil meals.
The moisture content of fishmeal is normally low in order to facilitate storage and transport. If the moisture content remains at the acceptable lower limits the meal will be more likely to have a low bacterial and/or mold count. Antioxidants must be added to the meal to ensure proper stabilization during extended periods of storage.
Fishmeal contains three major nutrients; protein, fat and minerals (ash).
Fishmeal is added to poultry diets as a source of highly digestible, "high quality", animal protein. Protein is added to poultry diets to supply the amino acids required for maintenance, growth and egg production. Animals synthesize proteins from 22 amino acids. However, animals cannot synthesize all 22 of these amino acids. Amino acids which can not be synthesized by animals, and therefore must be supplied in the diet, are classified as essential. Those that can be synthesized by the animal are termed nonessential. Of these, a few cannot be synthesized at a rate fast enough for maximum growth and, therefore, are considered dietary essentials.
The nutritional value of any protein is directly related to the amino acid composition of that protein. A protein that does not contain the proper amount of required (essential) amino acids would be an imbalanced protein and would have a lower nutritional value to the bird. Proteins of cereal grains and most other plant protein concentrates fail to supply the complete amino acid needs of poultry, due to a shortage of methionine and/or lysine. Soybean meal, which is widely used in poultry diets, is a good source of lysine and tryptophan, but it is low in the sulfur-containing amino acids methionine and cysteine. Fishmeal is an excellent source of all of these amino acids. A well-balanced protein, such as that found in fishmeal, is considered to be of high nutritional value for the bird.
Feedstuffs are combined to meet the bird's need for the most limiting amino acids, as well as other nutrients and energy. This can sometimes result in a higher than required protein content of the diet due to the presence of other amino acids in excess. The excess amino acids are not used for the function of protein synthesis. Instead they are deaminated and their carbon skeletons used as an energy source or stored for use as an energy source at a later time. This method of furnishing excess amino acids is very expensive and is an inefficient overall use of the dietary protein.
Using synthetic amino acids, diets can be formulated which meet the bird's amino acid requirements but with a reduced total protein content. This provides the appropriate levels of essential amino acids while avoiding large excesses of other amino acids.
Fishmeal contains an excellent quantity and profile of amino acids which can also offset the deficiencies of certain limiting amino acids in cereal grains. The protein in fishmeal is an excellent source of the essential amino acids lysine, methionine and tryptophan. It is because of this that fishmeal is often used as the supplement of choice for vegetable protein, especially soybean meal.