Gossypol is a natural yellow pigment found in small glands in the cotton plant and its seed. In its free form it is toxic to pigs, poultry, fish and young animals, so it decides how much cottonseed meal a feed can safely contain.
Adult ruminants tolerate it much better. That is why cottonseed cake is mainly a cattle and buffalo feed, as explained in what cottonseed cake is and which animals it is fed to.
Free and bound gossypol
Gossypol in meal exists in two forms. Bound gossypol has reacted with protein during heating and is largely unavailable to the animal. Free gossypol has not, and it is the form that causes harm.
Processing changes the balance. Heat during pressing and toasting binds more gossypol, which lowers the free fraction. But heavy heating also damages protein, especially the amino acid lysine, which lowers the meal's feeding value. A good plant aims for a balance between the two.
Why it matters by animal
- Pigs: free gossypol can depress growth and appetite, so inclusion is kept low.
- Broilers: high levels slow growth. Formulators limit cottonseed meal and often add iron salts to bind gossypol.
- Laying hens: gossypol can cause olive or greenish discolouration of egg yolks in storage, which leads to complaints.
- Young ruminants: calves and lambs whose rumen is not yet developed are more sensitive than adults.
- Breeding males: gossypol is known to affect male fertility in several species, so formulators take care with breeding stock.
- Fish and shrimp: tolerance varies by species, so feed makers set their own limits.
How it is regulated
Some importing countries limit gossypol in feed. In the EU, free gossypol is one of the undesirable substances covered by Directive 2002/32/EC as amended, with maximum levels that differ by feed type and animal. Other markets have their own rules or none. Check the current limit with your national feed authority, and with your customers, who may set tighter internal limits.
What to ask the supplier
Put the limit and the test method in the contract, as for any other parameter. The wider list is in what tests should be on a feed ingredient certificate of analysis.
- Free gossypol result on a recent lot, from an NABL-accredited lab, with the method named.
- Total gossypol if you formulate for sensitive animals.
- Process route: expeller, pre-press and solvent, or direct solvent.
- Available lysine or a protein quality indicator, if you want to check for over-heating.
- Consistency: results from several lots, not one, since seed and process vary.
Where we come in
We ask crushers how they press and toast cottonseed, then have free gossypol, protein and aflatoxin tested at an NABL-accredited lab on sealed samples. You see the original reports before you agree a price. Start with a free sourcing review.