Vermiculture in animal farming: A review on the biological and nonbiological risks related to earthworms in animal feed

Abstract Earthworms are part of natural diet of some farm animals such as poultry. They are a protein source. Unfortunately, earthworms can accumulate some toxic substances occurring in the soil and animals can be contaminated through feed containing these earthworms. The biological and nonbiological risks related to earthworms depend on the type of substrates through which they live. Earthworms are usually contaminated in polluted soil by various types of toxic and poisonous substance. The most common toxic compounds are heavy metals, pesticides and microbial toxins, which can lead to toxic or poisonous contamination of earthworms and then animals, such as poultry, fish and swine, through feeding. This risk cannot be identified in earthworm body without its destruction. But according to toxic substance targeted, there are many ways of risks detection, in soil, earthworms and animals. To protect farm animals, different technics are available. To limit heavy metal contamination, soil should be analyzed before collecting earthworms. Many treatments are available. By heating at 80°C for 2–4 h, microorganisms can be destroyed. Nevertheless, this technique needs to be adapted with certain types of bacteria whose enterotoxin withstands temperatures of 100°C for 30 min, or more. To limit all these risks, the use of earthworms reared from vermiculture can help to prevent contamination of poultry through feeding.