By-products from meat production can become an important fish feed resource, but cattle products must be avoided according to current legislation. NIFES is therefore developing a better method to determine where the by-products come from.

‘Many parts of slaughtered animals are not used for food, but still have high nutritional value. I like to ask my students how many of them have eaten liver casserole or blood pancakes. People used to be better at using the whole animal, but now there are fewer products that are not pure meat,’ says Robin Ørnsrud, head of research at NIFES.

The parts of the animal that don’t end up on the consumer’s table can become processed animal proteins (PAP). This can include blood meal, feather meal or meat and bone meal, much of which is a good source of protein and fat and is very suitable for use in fish feed.

‘PAP is primarily a resource,’ says Ørnsrud.

Prohibited since mad cow disease

Using animal by-products was prohibited in Europe for a long time following the outbreaks of mad cow disease a few decades ago. Using PAP from ruminants is still prohibited, but the rules have been changed for other species in recent years. By-products from chicken production etc. can therefore be used in fish feed.

‘It should really go without saying. It would be sensible to use it in the production of food. It’s about protein and fat, which are in short supply in large areas of the world,’ says Ørnsrud.

Important traceability

PAP used in feed is heated and ground. The result is then a highly-processed product that may be difficult to recognise. If animal by-products are to be used in fish feed, traceability is vital. It must be possible to determine what animal the by-product comes from.

There are currently two approved methods for finding this out. The most advanced method recognises DNA and can thereby identify what species the animal by-product comes from.

‘We are also developing a third method, where we use the PAP protein profiles to determine both the species and tissue,’ says Ørnsrud.

One of the advantages of the newest method is that you can find out what type of tissue the by-product comes from, e.g. blood meal or bone meal. If traces of beef are found in the feed, this method can help to identify the source of the contamination.

The new method will also be able to ‘acquit’ feed containing PAP from milk. The DNA tests around today cannot determine whether the PAP comes from milk or other parts of cattle, while the new method will be able to distinguish them from each other. This is important, as using PAP from cattle and other ruminants is prohibited in feed, while by-products from milk, such as whey, is allowed. This means that a more precise method will now be available, which is important to be able to correctly identify the illegal use of PAP from cattle in feed.

NIFES is working on further developing new analyses methods for PAP, with a view to using them to monitor feed in future.

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