Some horses really enjoy munching on acorns and oak leaves, especially young tender growth oak leaves. Others will eat acorns like candy. Horse people need to be aware that there are many types of plants and even trees that can be rather harmful to our horses. Most horse folks already know that wild cherry or choke cherry leaves are very toxic for horses, particularly in the freshly wilting stages. Add oak trees to the “not near or in our pasture” status.
Bottom line about acorns and oak leaves is don’t let your horse eat them. If he consumes enough of them, the horse may die.
The problem with acorns and oak leaves is the acidic chemical tannin – leaves and acorns contain tannin. If a horse ingests enough tannin and large amounts are known to be poisonous to horses, their liver and kidneys may be compromised. Tannin also obstructs the utilization of protein.
Tannin poisoning has no antidote and serious problems can result. Worst case scenario, results can be catastrophic.
Black or red oak leaves have the most tannin while white oak contains the least. In spring when the oaks regenerate leaves and later, as acorns develop and are in their unripe, green stage, the tannin reaches a peak toxicity. Once the foliage and acorns mature, tannin content declines.
Generally, oak poisoning in horses is not common since horses eat other forage but an owner should remain vigilant. Ingesting an acorn now and then will not usually harm the horse fed with good quality hay. It’s the horses that develop a taste for acorns that are in the greatest danger. In those instances, they should immediately be removed from the pasture and placed on a high ratio of high quality forage.
Some horses will develop mild colic due to indigestion after eating oak leaves and/or acorns. Some may founder. Others may get laminitis.
The signs of acorn poisoning can be loss of appetite, excessive salivation, blood in the urine or manure, colic like pain, slow or irregular heart-rate, elevated temperature, pale mucous membranes, watery eyes and depressed attitude.”
Worst cases have failing livers or kidney functions; other organs may be severely affected and start to hemorrhage.
Protect your horses with knowledge and good practices. Fence off any trees from pasture areas. Rid grazing land of leaves and acorns.
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