Garlic - The Miracle Herb?

I was always told that garlic was extremely beneficial to horses and ponies as it repels flies, naturally contains MSM (which is good for joints and allergies!), acts as an anti-septic and anti-inflammatory and is great for their respiratory system too. It seemed like it was a bit of an all round miracle herb with the added bonus of being cheap, completely natural and easy to get hold of! 

I'm currently doing a nutrition project for college and I've been looking into garlic and it's effects on horses  and its not as straight forward as I thought it would be. It seems that garlic, although good for humans, may be more damaging to horses then we are led to believe.

Garlic contains a chemical called N-propyl disulfide (also known as Allicin), which is toxic to horses, cattle and dogs! There is the argument that commercially bought garlic powders are better then feeding home grown or fresh garlic as the allicin is destroyed when dried using heat. But would this cause the garlic to lose some of its other good properties too? It is the allicin that causes many of the bad properties associated with garlic. Many companies vary the amount of garlic in their products too by mixing it in with bulking agents so it can be difficult to really tell how much garlic a horse is actually getting, so its always worth reading the ingredients on supplements!

How red blood cells function

Feeding too much garlic can cause painful gastric ulcers (which in turn can lead to internal bleeding), an acidity imbalance to the immune system and can cause Heinz-body anemia. Heinz-Body Anemia is when the red blood cell contains denatured (the proteins and/or the nucleus are damaged or destroyed) hemoglobin. It causes shortening of the red blood cell survival time and means they are easily damaged which in turn leads to the overall red blood cell quantity lowering. The red blood cells are how oxygen is transported around the body - so when these are damaged the horse can't give it's muscles etc enough oxygen (all cells need oxygen for survival!) to function properly hence it becomes anemic.  

But exactly how much is too much? Well, no one seems to know despite various tests being done. One link stated that 15 - 200 mg/kg body weight (so 7.5g to 100g for a 500kg horse) of dried garlic can cause adverse effects while another said feeding half to 2 ounces (half ounce is 14g, two ounces is 57g) is safe depending on bodyweight, but never specified what amount they recommend for each body weight (14g for a pony or do they mean a big hunter?).

Garlic doesn't normally grow in areas where horses like to graze so they wouldn't naturally come into contact with it, also if horses are given the option to eat it on its own they tend to avoid it. Horses are known to self medicate and will search for specific herbs in times of illness so maybe them avoiding fresh garlic is a sign they don't need it? We usually have to mix it in with hard feed or molasses to hide the taste and encourage them to eat it.

Which brings me to the method of feeding... fresh, frozen and dried. I couldn't find information about if feeding fresh is better or worse then dried garlic. Fresh garlic is 80% water so in theory the allicin level should be lower than dried garlic ...but then this would vary from plant to plant. I also couldn't find information about if feeding a large dose of garlic, say once a week, was more or less damaging then feeding a small dose every day.

My thoughts about feeling garlic to horses has done a complete 180 and I won't be feeding or recommending it again. There seems to be little scientific research to prove its benefit to horses and so many veterinary articles and books prove allicin causes anemia. I think for now I'll be playing it safe and avoiding it altogether. There are so many other herbs that are beneficial to horses but are over looked because of people just assume garlic is the best option to feed. .. the feed companies certainly keep telling us it's great! I will be exploring these other herbs over the coming weeks and will let you know how I get on!

Do you find your horse seems more sluggish since feeding garlic? Do you find it makes any positive impacts on their health?

(Links for further reading - LINK, LINK)