Onions: Poisonous Plant Of The Month

Onions are toxic, with both cattle and sheep being particularly susceptible. Learn the symptoms to look out for and what to do if onions are ingested.

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I like onions. I particularly like them in November when they’re fried and on my hot dog at a firework display. Onions, however, can be toxic to animals – I once had to treat a very ill spaniel that had stolen a salad containing a small amount of onion. Thankfully, she survived and recovered, but some animals with onion toxicity aren’t so lucky.

Onions (and garlic, too) cause the red blood cells to lyse, or burst, leading to anaemia. Clinical signs include weakness, staggering, inappetence, rapid breathing and heart rate, dark brown urine, pale or yellow mucous membranes and – unsurprisingly – onion breath. Secondary kidney failure can occur, and pregnant animals may abort. Toxicity can happen as a result of a one-off onion feeding session, or from smaller amounts ingested over a longer time. Raw, cooked, dehydrated and powdered onions or garlic can all have the same effect.

Both cattle and sheep are susceptible, and poisoning may happen from grazing onions or wild garlic, from deliberately or inadvertently feeding onions to livestock or from allowing animals access to stored onions. Onions can be quite tasty, and stock may eat large amounts in one go.

Affected animals should be removed from the onions. Multivitamin injections and iron can help, and blood transfusions can be given in severe cases – give us a ring if you need any advice!

Humans aren’t affected by onions in the same way, which is good news for me and my hot dog. No feeding leftovers to pets this bonfire night, though!

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