The oil seeds are grown mainly in tropical countries for the edible oil they contain. Oil cakes and extracted meals are the residues remaining after the removal of the greater portion of the oil from these seeds and fruits. The residues are rich in protein and are used as protein supplements or protein-rich concentrates.

Extracted: remove or take out, especially by effort or force.  
Percolate: (of a liquid or gas) filter gradually through a porous surface or substance.

The old method of removing the oil by hydraulic pressure is now obsolete. The modern method is to use the expeller screw-press or to extract the oil by means of an organic solvent. In the expeller process, the prepared seed is forced by a powerful screw along a constricting tube so that the oil is squeezed out. The residue is in the form of broken flakes and

usually has an oil content of 5 – 6%. Some charring may take place owing to the heat produced in the expeller. In the extraction process, a non-inflammable volatile solvent such as trichlorethylene is allowed to percolate through the coarsely- ground prepared seed, so that it dissolves most of the oil. The residue contains no more than 1 – 2%. Considerable care is taken to recover as much as possible of the volatile solvent and to ensure its complete removal from the extracted meal.

Sometimes the process is more complex in that the husk or hulls of the seed have to be removed before extracting the oil. This gives a residue termed decorticated cake or meal. Hence it is important to distinguish between:

  • Expeller nuts or meal;
    • Extracted meal;
    • Un-decorticated cake or meal;
    • Decorticated cake or meal and;
    • Extracted-decorticated cake or meal.

The method of preparation may considerably influence the feeding value of these products.


Whole ground nuts, including the shells, have an average content of 25% protein, which is of good quality. Though they are high in fibre, they are very rich in total digestible nutrients because of their fat content of 36%. They are deficient in carotene, low in calcium and not very rich in phosphorus.


Decorticated (without shells)

Feeding Value:

  • T.D.N. – 75%
    • C.P. – 40 – 48%
    • D.C.P. – 36 – 42%

Un-decorticated (with shells)

Feeding Value:

      Decorticated: remove the bark, rind, or husk from.

T.D.N. – 67%

  • C.P. – 30%
    • D.C.P. – 26%

The decorticated product has a fibre content of 6 – 10%, while theun-decorticated feed may be as high in fibre as 25%. Hence the difference in nutritive values. The corresponding extracted meals are lower in total digestible nutrients due to their very low oil content.

The quality of the protein of groundnut oil meal is good, ranking close to that of soybean oil meal, but it usually has less lysine. Groundnut oil meal is one of the best protein supplements for livestock feeding. It is well liked by stock. It is most commonly fed to dairy cattle and is very suitable for milk production. When fed to pigs, it tends to produce soft bacon, but this can be partly overcome by the use of the extracted decorticated meal.

Cotton Seed meal or Cake from Cotton, Gossypium L Decorticated

Feeding Value:

  • T.D.N. – 73%
    • C.P. – 40 – 45%
    • D.C.P. – 32 – 36%


Feeding Value:

  • T.D.N. – 50%
    • C.P. – 21 – 25%
    • D.C.P. – 18%

The better-quality cotton seed meal consists of the cake after the oil has been extracted and from which the lint has been removed. The quality will vary according to the amount of lint in the seed. A good quality meal is light yellow and has a sharp, nutty smell. A dark colour indicates that it contains a high percentage of shells and fibre.

Most of the cotton seed meal, including the local product, has 3% of fat or more. It supplies protein of satisfactory quality for cattle, sheep or horses, but as a protein source for pigs and poultry it is too low in lysine. Cotton seed meal is one of the feeds richest in phosphorus, containing 1.0% or more of that important mineral. By contrast, it has only about 0.2% calcium. Cotton seed meal tends to produce milk fat of a high melting point and hard body fat.

For pigs and poultry, the ordinary kind of cotton seed meal should be fed in strictly limited amounts, because of the danger of injury from a substance called gossypol which is found in cotton seed meal It is not safe to include more than 10% cotton seed meal in the ration of pigs, poultry and calves. The symptoms of gossypol poisoning are anemia, diarrhoea and eventually paralysis. If the ration of laying hens has more than about 5% of ordinary cotton seed meal, the yolks of the eggs are apt to develop an olive green or brown colour. The eggs may develop a pinkish color during storage.


Feeding Value:

  • T.D.N. – 43%
    • C.P. – 4%
    • D.C.P. – Nil

The hulls are low in calcium, very low in phosphorus and lacking in carotene. They should be fed with protein-rich feeds or a source of nitrogen. In this case they are about equal in value to fair-quality grass hay.


Without hulls

Feeding Value:

  • T.D.N. – 110%
    • C.P. – 30%
    • D.C.P. – 24%

With hulls

Feeding Value:

  • T.D.N. – 75%
    • C.P. – 15 – 17%
    • D.C.P. – 14%

The seed contains 25 to 26% of oil and so its use as a stock feed is limited. The oil content accounts for its exceptionally high T.D.N. value. It has a tendency to produce soft bacon and butter, and its protein is low in lysine.



Feeding Value:

  • T.D.N. – 75 – 80%
    • C.P. – 40%
    • D.C.P. – 35%


Feeding Value:

  • T.D.N. – 55%
    • C.P. – 20%
    • D.C.P. – 17%

The decorticated meal has a fibre content of approximately 14% and the un-decorticated about 30%. Sunflower seed oil meal is very palatable and keeps well in storage. When it is over-heated it becomes very deficient in lysine, due to the destruction of this amino acid.


Feeding Value:

  • T.D.N. – 60 – 65%
    • C.P. – 12 – 14%
    • D.C.P. – 11%

The entire sunflower head is frequently used as a feed for stock. As soon as the seeds are formed, the flower, plus about 0.3 metres of stem is cut and passed through a hammer-mill. The resultant meal contains up to 14% protein and about 25% fibre. The T.D.N. value is considerably influenced by the amount of seed which has a high oil content. It may be mixed with maize and used as a cattle feed.


Feeding Value:

  • T.D.N. – 88%
    • C.P. – 38%
    • D.C.P. – 34%

Soybeans are the richest in protein of all the common seeds used for feed. They are also high in fat, having 18%, but low in fibre with 5%. In total digestible nutrients, they rank even above maize because of their high fat content. Most black-seeded varieties of soybeans are somewhat lower in fat than the yellow-seeded. Soybeans are rather low in calcium, with only 0.25%. They contain 0.6% phosphorus.

For some unknown reason, feeding a. large proportion of soya- beans to cattle decreases the utilisation of carotene or vitamin A, and consequently increases the vitamin A requirement in the ration.

The nutritive value of soybeans and of soybean oil for non- ruminants, such as pigs and poultry, is increased by proper cooking. Such cooking greatly increases the availability and value of the protein for these animals and also destroys the trypsin inhibitor. This substance depresses the growth of non-ruminants and prevents the action of the protein digestive enzymes, trypsin and erepsin.

Raw soybean protein, therefore, has low value for pigs and poultry. Fortunately, properly cooked soybeans furnish protein which is nearly equal in value to the protein of milk or fish meal. Too high a temperature or prolonged cooking reduces the value, because it destroys, or makes lysine and certain other amino acids ineffective.

The protein of soybeans is rather low in the total amount of sulphur containing amino acids – methionine and cystine. However, this may be partially balanced by the amounts of amino acids contained in the cereal grains, if they are included in the ration. Soybeans should be ground for dairy cattle, but not necessarily for other stock. Soybeans which have been ground are apt to turn rancid if stored long in warm weather.

The ground pods and seeds which contain about 24% protein and 10% oil are occasionally mixed with a cereal and fed to cattle as a concentrate.


Feeding Value:

  • T.D.N. – 78%
    • C.P. – 41 – 45%
    • D.C.P. – 37%

The use of trichlorethylene instead of hexane in the solvent process produces a meal which is poisonous to cattle and certain other animals, This solvent should not be used to extract the oil from soybeans. Soybean oil meal is low in fibre – about 6%, and contains 5% oil. The solvent-processed oil- meal has only about 1.5% oil. For pigs, calves and poultry, the properly-cooked meal ranks ahead of all other plant protein supplements because of the high quality of its protein. Further, it is one of the best protein supplements for dairy cattle. The low-oil product is recommended for pigs to avoid the tendency of soybeans to produce soft bacon. Fed with a source of vitamin B12, its value as a protein supplement is only slightly less than that of animal protein. For poultry feeding, soybean proteins are deficient in methionine.



Velvet beans, cowpeas and jack beans are frequently grown for stock feed. They all have approximately the same general composition and feed value. Their protein content ranges from 23  to 33%, with a digestible protein value of 20%. They are relatively low in oil and fibre content.

Beans are not very palatable to stock: their digestibility is not particularly high when they are fed raw, especially to pigs, and their protein is of fair quality. Bean meals have the disadvantage of developing a rancid, bitter taste after a few weeks storage.


Feeding Value:

  • T.D.N. – 82%
    • C.P. – 23%
    • D.C.P. – 19%
      Rancid: smelling or tasting unpleasant as a result of being old and stale.

Velvet beans belong to several species of the genus Stizolobium and to hybrids between them. They are grown mainly for forage. When they are gathered for feeding to stock they are generally fed whole in the pod, or else the beans and pods are ground. Pods are from 50mm to 150mm long, and contain  three to six seeds.


Feeding Value:

  • T.D.N. – 74%
    • D.C.P. – 18%

Velvet beans in the pod and even when ground, are unpalatable, but they may be fed to dairy cows, beef cattle or sheep as a small part of the ration (e.g. 8 kg) daily for cattle. If too much is fed, they may act as a laxative. Dry beans and pods are satisfactory for fattening cattle.

However, for dairy cows, the value is increased considerably by grinding. If this cannot be done, the beans and pods should be soaked for 24 hours.

Velvet beans are most unsuitable for pigs. This has been shown to be true, regardless whether the beans have been fed shelled, ground, or as ground velvet beans and pods. They cause severe vomiting and diarrhoea.


Feeding Value:

  • T.D.N. – 78%
    • C.P. – 34%
    • D.C.P. – 20%

Jack beans are one of the well-known species of the genus Canavalia, which grows throughout the tropics. It is a bushy, annual legume which reaches a height of approximately 0.6 metres. It has the advantage of being hardy and drought-resistant and immune to most pests. The pods are from 200 to 250 millimeters long and contain 10 to 12 white seeds. The Jack bean is a high-yielding legume, from which 2 200kg per hectare may be obtained. The young pods and immature seeds (without pods) are eaten as a vegetable. The jack bean plant is considered a valuable green manure species  for the tropics and sub-tropics. Trials indicated that it is easier to mill and feed the complete pod and obviate the necessity for thrashing. Great care is needed in the feeding of Jack bean seed because it is a quantitative poison, i.e. it is very dangerous when a certain level is exceeded. Therefore, it should be mixed with other feeds and the amount of Jack beans incorporated should not exceed 20% of the total. Alternatively, the seeds may be cooked, as the injurious substance is destroyed by heat.


Feeding Value:

  • T.D.N. – 76%
    • C.P. – 23%
    • D.C.P. – 19%

Unfortunately, most varieties of cowpeas ripen unevenly therefore when the crop is grown for seed it is necessary to pick the pods by hand as they ripen. The plants may be cut when about three quarters of the pods are ripe and before the earlier-ripening pods are shattered or damaged. The cowpea (Vigna sinensis) is the most common species of the genus Vigna. It is an annual legume which is deep-rooted, vigorous and herbaceous. Cowpea seeds are used for human food and as concentrates for farm animals. For this reason, cowpeas are used mostly for forage.                                                                       

Cowpeas furnish protein of fair quality to supplement the cereal grains. They may be used satisfactorily as a protein supplement in feeding cattle, sheep and horses. For pig feeding, cow-peas are best fed in combination with a better-quality protein supplement.