Based on data collected in slaughterhouses, during autopsies and on farms, as well as data in the scientific literature, the ANSES working group estimated that in France at least 7 to 20% of cattle are reported to ingest metal foreign bodies. With a cattle population of over 10 million, this estimate provides an idea of the extent of the problem. The presence of foreign bodies in the stomachs of cows is linked to on-farm activities and has highly variable consequences on their health and welfare. In a small number of cases, the ingestion of foreign bodies can cause pain and severe injury. Each year, approximately 30,000 carcasses have to be totally or partially excluded from consumption due to injury caused by ingestion. The foreign bodies and associated injury also cause the death of approximately 29,000 cattle per year on farms. Taken together, these figures account for approximately 0.6% of the French cattle population.
Metal objects are the foreign bodies most commonly found in cow stomachs
The foreign bodies most commonly found in the stomachs of cows are wires of a few centimetres in length, followed by nails. Objects from activities around the farm are the most likely origin, such as metal components of old tyres used for securing tarpaulins over fodder or silage, bits of fencing broken off when cutting hedges, and waste from building sites. “All types of livestock farming are affected, whether indoors or outdoors, but counter-intuitively, cows living indoors seem to be more exposed than those grazing outdoors,” says Charlotte Dunoyer, head of the Unit for the assessment of risks related to animal health, nutrition and welfare. Using mechanised methods to bring fodder in from outside tends to “concentrate metal fragments” in the distributed feed, which does not happen when animals spend more time grazing outdoors. For example, pieces of fencing that have fallen off may be picked up along with the cut grass, and wire from old tyres may fall into the silage.”
Best practices to reduce exposure of cows to metal fragments
The first step to avoid injury from ingestion of foreign bodies is to act at the source. Experts have issued recommendations to avoid the presence of metal fragments in the cows’ environment. Recommendations include avoiding the use of old tyres to secure tarpaulins over fodder and installing electromagnets on farming equipment used for feeding to attract ferromagnetic objects. Particular attention should also be paid to the maintenance of fences and hedges, as well as building sites around cattle farms, to ensure than no metal fragments are left behind.
Magnets to prevent serious injury
To prevent the occurrence of serious injury, cattle farmers quite often use magnets. Magnets of a few centimetres in length are placed in the cow's stomach via oral administration. By attracting and trapping metal fragments, the magnets stop them migrating and causing injury to fragile organs, such as the heart or diaphragm. These devices have been proven to be effective. For example, studies on dairy farms in Quebec have shown that animals which have a magnet inside them are half as likely to be diagnosed with a disorder caused by the presence of foreign bodies as animals without a magnet.
Magnet administration poses an extremely low risk to animals’ welfare as literature data indicate that trauma following oral administration of a magnet is rare. In terms of public and animal health, “The risk of the magnet dissolving appears to be negligible over the lifetime of the cow,” says Nibangue Lare, who coordinated the study. “However, the working group considered the worst-case scenario. Even if the magnet degraded within a year, the constituents of its components would not pose a health issue for animals or for humans consuming animal products.”
Experts recommend the administration of a magnet at the first suggestive signs to avoid the development of serious symptoms, and also depending on the animals’ risk of ingesting metal objects. In particular, the use of a magnet may be considered if other animals in the herd have already been affected by the ingestion of foreign bodies or if the farm is located in a high-risk area, such as former conflict zones or military grounds. Limiting the risks associated with the ingestion of foreign bodies therefore relies on preventing the risk of ingestion in the first place and then limiting its effects.