Still better detection of drug residues in slaughterhouses

The use of sophisticated detection methods in slaughterhouses increases the need to work precisely when using medicine. In liquid feed plants, it is difficult to completely exclude the possibility of the transfer of drug residues.

Last autumn, the pig slaughterhouses urged their suppliers to work accurately when administering medicine and dewormers and to correctly fill in the forms for food chain information (VKI). The reason for urging pig farmers to dot the i’s and cross the t’s was the announcement by the Dutch Food and Consumer Safety Authority to carry out extra checks on slaughterhouses for unwanted residues.

“Within a week I received a letter from two slaughterhouses. Careful handling of anthelmintics was insisted upon. The second encouraged people to fill out the VKI form properly’, says pig farmer Jan van de Weem, manager of Manstal Meat Production in Melderslo, Limburg.

“For me, these calls were a reason to take a closer look at how we handle deworming and antibiotics here in the company,” says Van de Weem. ‘I thought we were doing well, but a critical look made it clear that dotting the i’s and crossing the t’s is not a luxury.’


It is not a superfluous luxury to dot the i’s and cross the t’s

Jan van de Weem, pig farmer in Melderslo

The entrepreneur concluded that the liquid feed installation that supplies all the pigs on the farm is a risk factor. “There is a feed line that runs through all departments. We flush that pipe with clean water four times a day. This greatly reduces the risk of transmission. However, the rinse water is used again to make the next liquid feed mixture. In theory, very small amounts of drug residues can end up in all pigs on the farm.’

Slaughter-ready pigs may inadvertently ingest residues of medication or anthelmintics through liquid feed. © Hank Riswick

For Van de Weem, his analysis led him to shift the time he wormed to another day of the week. ‘We worm pigs twice with an interval of five weeks. We always did that on Tuesdays. We deliver pigs ready for slaughter on Thursdays and Fridays.’

There was thus a minimal chance that anthelmintic residues would end up in the feed for pigs ready for slaughter, explains the pig farmer. “The waiting time for the anthelmintic flubendazole is five days. By moving the deworming to after delivery of the heavy pigs on Friday, we can largely rule out the risk of deworming residues in the feed for the pigs ready for slaughter.’

It is difficult to administer flubendazole differently

Van de Weem has also thought of administering the anthelmintic in a different way. ‘But it is difficult with flubendazole. The agent is very poorly soluble in water, which makes application in the trough with a watering can difficult. It may be an option to choose another anthelmintic that can be dissolved in water.’

Although it is not often necessary to use antibiotics, Van de Weem also took a critical look at his method of treating slaughter pigs with medicine. “One of the rules is that you report treatments on the VKI form no later than 60 days before slaughter. What shocks me is that fattening pigs grow so fast these days that sometimes you get within sixty days without noticing it’.

Slaughterhouses asked their suppliers to pay extra attention to preventing residual products.
Slaughterhouses asked their suppliers to pay extra attention to preventing residual products. © Hank Riswick

The fastest growers go to the slaughterhouse between seventy and eighty days after laying, the entrepreneur states. ‘This means that I have to register all medication used from fourteen days after application on the VKI form for these frontrunners. I also have to tin these treated pigs to keep them recognizable. I also give them a color with an aerosol on the inside of one ear so I have a good idea of ​​the growth trajectory they have been treated in.’

If Van de Weem considers herd treatment with medicine necessary, he does it not via the feed, but with a watering can in the troughs. In this way, he rules out the risk of transfer to other departments.

Transfer of drug residues

Suppliers of liquid feed installations recognize that most installations involve a risk of transfer of pharmaceutical residues. ‘With a well-maintained installation, where you know for sure that all valves and valves are working correctly, it is indeed a small risk,’ says Peter van Mierlo from the supplier Kampplan in Boxtel. ‘But with a circular circuit, the chance of transmission can never be completely reduced to zero.’

One option to combine medication use and liquid feeding without the risk of cross-contamination is to work with conduits per department. A branch line is not part of a circuit. There is always food in it. If you add medicine directly into the conduit with a dosing device, it can only end up in the feed trough. “In Germany you see this regularly. In the Netherlands, there are still not many companies where the wet feed installation is designed like this,’ says Van Mierlo.

Do not use liquid feed installation

Failure to use a liquid feed installation when administering products to the pigs is the best way to prevent the risk of unwanted residues in the meat, says liquid feed advisor Jos Adriaans from feed supplier Fransen Gerrits in Erp, North Brabant.

Adriaans: ‘Choosing medicine via drinking water is not an alternative. Many pigs fed liquid feed do not use the teat. You are dependent on managing resources with a watering can in the trough. It works fine, but it needs a lot of work.’

NVWA is getting better and better at applying

The Dutch Food and Consumer Safety Authority (NVWA) is constantly working to improve methods for detecting unwanted substances in food. Last spring, NVWA published the first results of a test with an innovative detection method. This works on the basis of biomarkers. These are indicators in the body’s cells that say something about residues of, in this case, drug residues.

The NVWA also tested the new technique at pig slaughterhouses and published the results a few weeks ago. Of the total of 170 test samples taken, 4 contained too many antibiotics. It involved a sow, a weanling pig and two half-grown meat pigs, the so-called cull animals. These are animals whose careers have ended or animals that are slaughtered prematurely. This concerns 4 out of 54 results of slaughtered animals. “We think it’s too high,” said an NVWA spokesman.

Food chain information form

The lawsuit also made it clear that farmers do not always fill out the food chain information form truthfully. The carcasses and offal of these animals have been destroyed. Farmers who failed to report the use of drugs on the form received a written warning.

NVWA reports that pig farmers are responding to the call from slaughterhouses to fill out the VKI forms better. The authority emphasizes in the same announcement that in the coming year it will keep a close eye on whether sector parties keep each other on their toes, such as respecting the required waiting time after administering veterinary medicine.

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