Garlic, onions and other similar foods such as leeks, chives and shallots contain n-propyl disulphide, which is a toxic component for horses. N-propyl disulphide can destroy red blood cells which leads to a condition known as Heinz Body Anaemia.
Cabbage, broccoli & cauliflower – Can cause severe gas if eaten in large amounts. Rhubarb – The leaves contain calcium oxalates, which can damage digestive & urinary systems and cause kidney failure. Dairy products – Horses are lactose intolerant, so cheese, milk, yoghurt & ice cream should be avoided.
No, eggs aren't really bad for them. Equine experts tend to agree that mixing in eggs with feed isn't a big issue, as long as the horse doesn't mind. We all know eggs are a great source of protein which have an ideal balance of amino acids, minerals and vitamins.
Spoiler alert: horses are herbivores! Their entire digestive system is designed to process plant matter. Horses, as a species, do not eat meat. While there have been many cases of horses eating animals and animal products, it is NOT the norm.
All this might all seem a little weird but in Iceland, horses are routinely fed dried fish throughout the winter for extra protein. During Scott's expedition to the Antarctic the ponies he used were fed fish meal with their rations.
Like most animals, horses are lactose intolerant, so it's important to keep them away from dairy products like milk and cheese. If you did give your horse dairy? He or she could suffer from diarrhoea.
Almost any fruits, and many vegetables, are safe treats for healthy horses. Apples and carrots are traditional favorites. You can safely offer your horse raisins, grapes, bananas, strawberries, cantaloupe or other melons, celery, pumpkin, and snow peas.
Vegetables Not Safe for Horses
These vegetables are absolutely NOT safe for your horse to eat: avocados, Brussels sprouts, cabbage, onions, regular potatoes, tomatoes, and peppers. Avoid feeding horses these vegetables at all costs!
Under no circumstances should tomatoes be fed to horses, she says. They contain multiple toxins in the fruit and plant that are poisonous to horses and many other animals. Tomatoes come from the Solanaceae family, which also includes deadly nightshade and many other toxic plants.
Weeds: Onions/garlic, ground ivy, milkweed, bracken fern, cocklebur, horsetail, white snakeroot, St. Johns wort, star-of-Bethlehem, sorghum/sudangrass, yellow sweet clover, blue-green algae, bouncing bet, larkspur, mayapple, skunk cabbage. Trees: Black locust, oak (green acorns), horse chestnut, boxwood, holly.
Onions, garlic, leek, shallot and chive are from the Allium genus of plants, which are toxic to horses if ingested. The plants contain propyl disulfide which can lead to the formation of oxygen free radicals that damage the membrane of red blood cells, causing cells to release haemoglobin.
In horses that ingest avocados, the toxin can cause colic, irregular heartbeat, respiratory distress, neurologic dysfunction, edema, and other signs of illness. Horse owners should not feed avocados to their horses, and should not allow the animals to graze in areas where they might have access to avocados.
Potato poisoning in horses only occurs when a horse is fed a large amount of potatoes, which are sometimes viewed by farmers as cheap and filling feed. Such feedings, however, are dangerous because horses are vulnerable to alkaloids, chemical compounds found within the potato and other members of the nightshade family.
Even a vegetarian pizza is not going to be good for your horse (not especially good for humans either). They don't need the cheese, salt, sugar, fat, spices etc. It could end up causing colic or choke as well.
Can horses eat peanut butter? Unless your horse has underlying health conditions, peanut butter is a safe treat to offer in moderation. In fact, peanut butter is not all empty calories – it has some nutritional benefits that can actually make it a healthy treat for horses if given sparingly.
One carrot contains about 230 milligrams of potassium. (source) Due to this relatively high potassium content, carrots are not suitable for horses with HYPP. You should never feed them carrots or any treats that contain potassium.
Can Horses Eat Cucumbers? Yes, horses can eat cucumbers – a welcome answer to those of you with an overabundance of cucumbers growing in your gardens. Cucumbers are a fantastic source of vitamins such as A, K, and C, as well as potassium. What's more, cucumber skin provides horses with a natural dietary fibre.
Bread is also high in starch and if your horse has equine metabolic syndrome and is insulin resistant, bread could lead to laminitis and founder. So although many items like bread are not toxic to horses, it is still not a good idea to feed these items as there are much healthier choices for equine feeds.
Watermelon is not harmful to horses. In fact, it is a great treat. In some European countries, watermelon rind is a common horse treat, though it should be cut into small, easy-to-chew pieces. If large pieces of rind are given, horses may choke.
Regular Coke has far too much sugar and could cause the horse to get laminitis.
Safe treats for horses
Other non-traditional, yet still perfectly acceptable foods include bread, pasta, macaroni, potato chips, fruit juice, hot dogs, hamburgers, and most dog and cat foods.
Ice Lollies are Ideal
You can make ice lollies from whatever food is normally part of your horse's diet, such as apples and carrots, and freeze these things in water overnight. Your horse will enjoy licking the ice lolly throughout the afternoon and it will be helpful in keeping him cool.