Due to current events, we would like to draw your attention to the danger of poisoning your grazing horses: In recent weeks, there have been repeated cases of sycamore poisoning in Germany. Horses that have access to areas with or near sycamore maples (Acer pseudoplatanus) are particularly at risk.

The toxic substance hypoglycin A is found in seeds (the typical wing fruits), seedlings and young shoots of various maple species. Horses usually eat these plant parts when there is not enough grass in the pasture, for example in the fall.

The toxic amino acid hypoglycine A leads to so-called atypical pasture myopathy in horses, a severe and sometimes fatal disease. After ingestion of the toxin, there is massive damage to the muscles, which manifests itself in significantly increased muscle values (CK, LDH, AST) and leads to pronounced myoglobinuria (red-brown urine).

You should look out for the following symptoms: generalized weakness, stiffness, colic, rapid breathing (tachypnoea) and increased pulse rate (tachycardia), altered urine color.

Unfortunately, the disease is often fatal in horses with pronounced symptoms; 60-70% of affected animals do not survive despite intensive treatment.

Hypoglycine A can be detected directly from the serum (1 ml) and provides important diagnostic information. In peracute cases of pasture myopathy, values of over 1000 nmol/L were found. If the values are below 100 nmol/L, it is possible that only small amounts of the toxin have been absorbed or that the absorption took place several days ago. It should be noted that the toxin is usually broken down in the animal within a few days.

An evaluation of the samples sent to our laboratory in 2025 shows a significant increase in the number of cases since October: around 87% of the samples sent in for hypoglycine A analysis were positive, and of these, around 35% showed extremely high concentrations of between 2000 and 8000 nmol/L, while the majority of the others showed double-digit values.

Prevention is crucial: Horses should not be put on pastures with or near sycamore, especially in fall (seed fall) and spring (seedlings). As the wing fruits in particular can be spread far and wide by the wind, haystacks and standing water should also be checked. The poison is water-soluble and can therefore contaminate the drinking water. A good supply of feed in the pasture and regular checks are the best protective measures.