Plants and Animal Protein Sources in Livestock Feed

Protein is one of the most important elements of animal feeds. It has numerous benefits and function in the productivity of animal feed. There are two main sources of
protein in animal feed, which include:

1. Animal protein
2. Plant Proteins



Linseed meal is a by-product of flaxseed when the fat is extracted. It contains 35% protein. Linseed meal is sometimes used in laying hen diets to increase the omega3 fatty acid content of eggs.


Canola was developed through conventional plant breeding from rapeseed, an oilseed plant already used in ancient civilization as a fuel. Rapeseed was once considered a specialty crop in Canada; canola has since become a major American cash crop.

Canola meal contains approximately 40 percent crude protein. It is an oilseed meal used to supplement and sometimes replace soybean meal in poultry feeds, particularly in the northern latitudes of the United States and Canada.


Ground peanut kernels with the fat extracted is peanut meal. The protein content is approximately 35% but varies depending on the amount of hulls and the method used to extract the fat. Peanut meal is a fair source of protein for poultry.


Soybean meal is the most commonly used plant protein source. Most commercial diets contain large amounts of soybean meal. It is a very palatable supplement, and contains either 44% or 48.5% protein, depending on whether or not the hulls have been removed during the oil extraction process. It is usually the most economical protein source for animal diets produced in the US.

Raw soybeans contain several anti-nutritional factors, including protease inhibitors, which can negatively affect protein digestion and bird performance. However, these inhibitors are destroyed by heat during the processing of soybean meal. Properly processed soybean meal is an excellent protein source for all classes of poultry, with no restrictions on its use.


Compared to plant proteins, animal proteins are higher in quality because of a better balance of essential amino acids.


Fish meal is made from dried and ground fish and fish by-products. It contains approximately 60% protein. Fish meal is occasionally used in poultry feeds but high cost tends to limit its usage. Too much fish meal in a poultry diet will result in the eggs an Most of the fish meal available in the United States goes either into the aquaculture or pet food industries.

Fishmeal is an exceptionally good source of high-quality protein, and its price usually reflects this. It also provides abundant amounts of minerals (calcium, phosphorus and trace minerals), B vitamins and essential fatty acids. The presence of unidentified growth factors is another feature of fishmeal. Feed formulations therefore seek to ensure minimum levels of fishmeal in diets.

Fishmeal consists essentially of dried, ground carcasses of fish. Good-quality fishmeal is brown, but the colour varies according to the type of fish used and the processing conditions. A very dark colour is indicative of overheating, which can destroy amino acids, reduce amino acid availability and substantially lower the protein quality.

Fishmeal is an important – sometimes the only – source of animal protein ingredients in most developing countries. It is either imported or locally produced. Local fishmeals typically contain between 40 and 50 percent crude protein, compared with more than 60 percent protein in imported fishmeals.

Local fishmeals are generally of low quality owing to lack of control over raw fish quality, processing and storage conditions. They are often adulterated with cheap diluents, including poor-quality protein sources (dried poultry manure, oilseed meals), urea and non-nutritive diluents such as sand. Some fishmeals may be objectionable because of putrefaction, impurities or excessive salt content. Samples containing as much as 15 percent salt are not uncommon.

This situation underlines the lack of quality control measures in most developing countries. As salt has laxative and growth depressing effects, the salt content of fishmeals should be carefully monitored; it should be less than 3 percent for best results, but legally may be up to 7 percent. The correct quantity of fishmeal to include depends on the types of cereal and oilseed meals in the feed formulation.

The cost of fishmeal is another important determinant. In general, average inclusion levels may be up to 8 percent for young birds, and less than 4 percent for older meat birds and layers. Higher levels must be avoided in finishing and laying diets, as they may lend a fishy taint to meat and eggs. Use of fishmeal can compensate, to an extent, where husbandry conditions are less than ideal.

Future expansion possibilities in fishmeal production are limited. Production does not seem to have increased over the past 20 years, and is unlikely to do so in the future, given the pressures on world fisheries. Fishmeal is included in the overall animal protein ban in Europe, and there is also an underlying concern about possible pollutant (e.g., dioxin) levels in fishmeal.


This is produced by cooking animal tissues and bones under steam pressure and then grinding them. This meal has a protein content of 50% to 60%., and is a common source of protein in poultry rations. Meat meal contains relatively high levels of protein, calcium and available phosphorus.

Meat meal is the dry-rendered product from mammalian tissues, excluding hair, hooves, horns, hide trimmings, blood and stomach contents, except in such amounts as occur in good slaughterhouse practice. Meat meals are derived mainly from bones and associated tissues such as tendons, ligaments, some skeletal muscle, gastrointestinal tract, lungs and condemned livers.

Variation in the proportions of these raw materials contributes to the large variations in meat meal quality. Depending on the proportion of bone to soft tissue used in the manufacture, the finished product is designated as meat meal (containing more than 55 percent crude protein and less than 4.4 percent phosphorus) or meat and bone meal (containing less than 55 percent crude protein and more than 4.4 percent phosphorus).

Collagen is the major protein in bone, connective tissue, cartilage and tendon, and contains no tryptophan. In poor-quality meat meals, 50 to 65 percent of total protein may be collagen. Increasing the level of bone in meat meal lowers the nutritive value, and the quality of its protein may vary greatly in terms of amino acid composition and digestibility.

Protein quality is also affected by the temperature used to process the meat meal. As a supplement to cereal-based diets, meat meal is of lower quality than fishmeal or soybean meal. Tryptophan is the first limiting amino acid in meat meal for poultry fed maize-based diets; lysine and methionine are also limiting.

Normally, no more than 10 percent meat and bone meal is recommended for use in poultry diets, largely because phosphorus requirements are met at that level. In recent years, feed manufacturers have to cope with increasing safety concerns, exemplified by the bovine spongiform encephalopathy (BSE) crisis, associated with the feeding of meat meal to ruminant animals. The use of meat meal in animal feed manufacture is now banned in some parts of the world, and the long-term future of this raw material seems uncertain.


This poultry by-product is very high in protein. The meal is made by rendering clean poultry carcass parts and grinding the product into a meal.

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