ENGLISH VERSION just a few dozen grams daily causes toxins to accumulate in the liver. The first symptoms may not appear until several weeks or even months later: recurrent colic, jaundice of the mucous membranes, weight loss, and more. Beyond a certain threshold, the liver is no longer able to perform its detoxification role. In the acute form of poisoning, if a horse ingests 3 to 5 percent of its body weight in ragwort over a short period, death can occur rapidly following the onset of digestive and neurological disorders such as agitation, poor coordination, and impaired vision. Horses do not normally eat ragwort because its bitter taste is highly unappealing. However, they may resort to it, or to other unpalatable toxic plants, during periods of forage shortage or when these plants are incorporated into hay. Once dried, ragwort loses its bitterness and horses no longer avoid it. Every breeder or horse owner should therefore be capable of examining hay and identifying undesirable species. Yet this requires real expertise, since dried plants are even harder to recognize. It is advisable to inspect fields before mowing or request guarantees from hay suppliers. It has also been observed that plants can be more toxic in some years than in others, depending on geographical location, rainfall, and environmental conditions. Plants do not always display the same“ character,” much like wine vintages. Climate change is also encouraging the spread of new enemies of the horse. Flatweed( Hypochaeris radicata), whose flower resembles a dandelion, expanded dramatically following the drought of 2003. Originally confined to southern regions, it has now spread throughout France. Its long taproots allow it to survive drought conditions that kill surrounding beneficial species. Horses, which are not naturally attracted to flatweed, may then begin consuming it. The plant can trigger Australian stringhalt, a condition characterized by involuntary hyperflexion of the hock. In severe cases, horses move with small hopping motions reminiscent of a rabbit. The exceptionally early and intense heatwaves recently experienced in France, including record temperatures for the month of May, suggest that this phenomenon of opportunistic, colonizing undesirable plants will only intensify.
Knowledge Is the Best Remedy Some plants act more subtly, such as black locust( Robinia pseudoacacia). Although the entire tree is toxic, its bark is particularly problematic. Yet its wood is widely used to manufacture fence posts, often without removing the bark.“ When horses have enough grass, they do not tend to eat bark. But if forage becomes scarce, they may start chewing on it,” explains Nelly Genoux.“ A relatively small dose can be fatal. Black locust posts can therefore be used safely, provided the bark has been removed.” But first, people need to know this. Many equine misfortunes could be avoided if their human guardians better understood their environment and adapted accordingly. For example, having oak trees in hedgerows is not a problem, provided horses can be removed from the pasture when acorns fall to the ground in autumn. The tannins contained in acorns can be fatal, causing a variety of disorders including anorexia, colic, and kidney or liver failure. Knowledge and proper pasture management remain the most effective tools against toxic plants. Fields should be regularly topped or mowed to eliminate areas of rejected vegetation. Bare patches should be reseeded to prevent weeds and invasive species from establishing themselves. It is also essential to avoid overstocking and overgrazing pastures so that they retain their floral diversity and ecological balance.
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The French Horse and Riding Institute( IFCE) makes Equipedia available to the public, a comprehensive knowledge base covering a wide range of topics. Designed for a general audience while maintaining scientific
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