Are fruit trees safe in horse pastures?

Some species of trees pose a threat to equine heatlh.
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Some species of trees pose a threat to equine heatlh.

Q: We just bought a property that has a very small orchard. We would like our horse to have the freedom to roam everywhere, but we haven’t been able to find out much about any risks the fruit trees might pose to him. The orchard has one or two trees each of oranges, lemons, avocados, loquats, pomegranates and figs. Our horse has pre-metabolic syndrome, mild Cushing’s and laminitis, but he is actually very healthy. Should he be allowed access to the trees? What do horses do with pits---spit them out or swallow them?

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A: Orchards can be wonderful for the family but are not always the best for your horse. With fruit trees, you have to be concerned about the horse eating not only the fruit but also the pits, leaves and bark. Depending on the tree, each part may present a separate danger. Keep in mind, too, that the horse may beat you to the harvest and leave slim pickings for the family.

Horses can acquire a taste for all of the fruits on your property, none of which themselves pose a problem if eaten in small quantities, except maybe avocados. However, your biggest concern with allowing free access to the orchard would be the total amount of fruit your horse could consume. With this selection of trees, he would have access to fruit almost year-round. For a horse with a history of laminitis and in the early stages of Cushing’s0 disease, I would not recommend free access to the orchard because the fruit has a high sugar content. Here are some individual characteristics and concerns with the different fruit trees in your orchard: 

Oranges and lemons

Fruit: These citrus fruits are not harmful. Horses can acquire a taste for them, and some eat the whole fruit, peel included. Oils found in peels may be irritating to the lips and corners of the mouth. Dried citrus pulp (the leftover material from juice production) is a common ingredient in livestock feed and can be used in horse feed in limited quantity.

Seeds: Orange and lemon seeds are not harmful to horses in small amounts, although no research has been done on consumption of larger quantities. High-protein seed residue can be used in cattle feed. Orange seeds are used in human herbal medicine for urinary tract ailments and malaria. Lemon seeds have been used as a natural anthelmintic in children, and the oil is prized as an antioxidant used in lotions and cosmetics.

Tree bark: Horses tend not to bother the bark on these trees; it must be bitter or strong tasting. The oils found in the bark can be irritating to the skin.

Leaves: Because the leaves are bitter, horses tend to avoid them. In humans, orange leaves are used for digestive issues and lemon leaves for colic.

Another note: Free access to lemon trees could be problematic because the branches have thorns.

Avocados

Fruit: The fruit of the avocado contains a compound called persin that is dangerous to livestock (although harmless to people). Persin is an oily fungicidal toxin that, it is believed, the trees create as a defensive mechanism against insects and fungi. Consuming large amounts of this toxin can cause noninfectious mastitis, gastritis, colic and possibly damage to the heart. Reports exist of horses consuming avocado without ill effects, but there is always a potential for problems.

Pit: The pit of the avocado is large enough to pose a choking threat if the horse does not chew it adequately. While the avocado pit is high in protein, it also contains persin and is high in tannins, which if consumed in large quantities are destructive to the intestinal tract and kidney.

Leaves: The avocado tree leaves contain toxic compounds, including persin, dopamine and methyl chavicol. The toxicity can vary in severity depending on the variety of avocado tree.

Tree bark: Essential oils (methyl chavicol and anethole) found in avocado tree bark have an anise odor that can make it appealing to horses, but the presence of persin renders it nocuous.

Loquats

Fruit: Eating large amounts of loquats can have a mild sedative effect in people, but this is undocumented in horses.

Seeds: Loquat seeds are not an advisable treat for horses because they contain small amounts of toxic alkaloids and cyanogenic glycosides (including amygdalin) that form cyanide in the digestive tract. The bitter taste will usually prevent horses from eating enough seeds to suffer from glycoside poisoning.

Leaves: The leaves of the loquat also contain small amounts of cyanogenic glycosides as well as ursolic acid and oleanolic acid, both of which have hypoglycemic (low blood sugar) and antihyperlipidemic (low blood lipids) effects on animals. In addition, the young leaves contain saponins, glycosides that protect the plant against microbes and fungi but are toxic to animals. Loquat leaves have been used in Oriental medicine for centuries and are thought to have wondrous curative properties. For horses, there are no known benefits to consuming loquat leaves.

Pomegranates

Fruit: Pomegranates are an excellent sweet treat for horses, and they are high in polyphenols (antioxidants). The whitish membrane between the pulp and seeds can be bothersome to humans (and slightly bitter) but is of no concern to horses, who will eat the entire pomegranate if given the opportunity.

Seeds: Separating the seeds in the pomegranate from the pulp is difficult unless it is squeezed for juice, and horses will usually not bother. Oil in the seeds contains punicic acid, the isoflavone genistein, the phytoestrogen coumestrol and estrone, the combination of which is being researched for anticancer properties. However, none of these compounds are believed to harm horses.

Tree bark and leaves: The bark and leaves of the pomegranate tree are high in tannins. The bark con- tains several alkaloids, including isopelletierine and has been used for centuries as a treatment for tapeworms in humans.

Figs

Fruit: Figs provide a sweet, tasty treat for horses, and their high sugar content makes them an excellent substitute for sugar cubes or other less healthy treats. However, avoid allowing free-choice consumption to a horse with Cushing’s or equine0 metabolic syndrome. Figs are palatable to horses fresh or dried.

Seeds: The seeds have a desirable omega-3 to omega-6 fatty acid ratio, although they are virtually inseparable from the pulp of the fruit.

Leaves: The leaves are used as feed for cattle in countries like India. No known toxins for horses are present in the leaves. Mostly, horses leave fig leaves alone.

Tree bark: The sap (latex) of the fig tree oozes abundantly when branches are cut and can cause skin irritation or contact dermatitis in sensitive individuals. Unripe figs also contain latex and should not be eaten until ripe.

On a more general note, horses can acquire a taste for many different types of tree bark and some will consume large amounts of it. Sometimes they do this out of boredom and other times because the bark is particularly tasty. Either way, this behavior can endanger the health of the tree and limit fruit production, because girdling the tree will kill it. It is only a problem for horses if there is a chemical in the bark that is toxic. Otherwise, they are consuming a lot of indigestible fiber. The problem with tasty leaves is that horses may denude the tree, compromising its ability to survive.

If the orchard is expected to produce reasonable amounts of fruits, it may require some periodic spraying of pesticides. This would certainly be a time when you would not want to allow your horse to consume any part of the tree or surrounding grassy areas because of the possibility of poisoning from the chemicals sprayed on the trees.

Again, due to all of these potential problems, I think it would be advisable to fence off your orchard to prevent your horse from having free access to the trees and their fruits. Both your family and your horse will be able to benefit more from rationing the ripened fruit and enjoying the harvest over a longer period of time.

Kathleen Crandell, PhD Kentucky Equine Research Boyce, Virginia

This article first appeared in EQUUS issue October 2014, #445.