I've heard of not so little number of horses that died because of colic that happened just because the owner gave his horses fresh cut grass.
And I have found a lot of different opinions on the net:
There is a LOT of moisture in freshly cut grass. Plus, in order to graze, a horse must take bites and then chew what it bit off. This is a process that triggers the proper enzymes needed to break down the forage. When put in front of a pile of fresh mown grass, the horse just gobbles it down quickly in a mass. The lack of enough time to produce the proper enzymes and the large mass plus all that moisture quickly lead to a gut imbalance. Now, grass starts fermenting as soon as it gets the least bit warm. In a nice, dark environment, it starts fermenting and letting off vast quantities of gas, there's too much for the horse to digest and he colics big time.
(Can you feed just cut grass clippings to horses? - Yahoo! Answers
Also find this:
"Feeding lawn clippings will dramatically upset the balance of microbes in the hindgut, potentially leading to colic or laminitis," said Larry Lawrence, Ph.D., a nutritionist with Kentucky Equine Research (KER).
"The amount of highly fermentable carbohydrates in regularly clipped lawns is dangerously high.
Excessive intake results in a high rate of fermentation in the hindgut. Accelerated hindgut fermentation can produce increased amounts of volatile fatty acids, which, as their name implies, are quite acidic," continued Lawrence.
"In addition to volatile fatty acids, a surplus of lactic acid will be produced. Lactic acid is not utilized or absorbed well in the hindgut. This increased concentration of acids brings about a condition called acidosis that lowers the pH of the hindgut.
"The acidic environment created by fermentation of grass clippings in the hindgut causes microbes to die, releasing into the bloodstream endotoxins that can cause laminitis," said Lawrence.
(from Lawn clippings dangerous fare for horses | Horsetalk - Horse nutrition and feeding articles and information
- You should remember there are some toxins and toxin-generators (like fructans) in both regular grass and clovers that will not change when cut.
- If it has been put in a pile and begun to ferment it may have formed botulinum toxin.
- If it is tainted with oil and gas that is not so good, but I doubt the horses would eat it.
- And there is no doubt grass mown with a lawn mower will choke a horse in a heart beat. I saw 2 horses that choked simultaneously on lawn mower clippings. I think the finely clipped grass is luscious to them and they attempt to swallow large amounts without chewing well.
So lawn mower clippings should go on to the fermentation pile but a pasture mown with a rotary pasture clipper (bushhog) is probably safe as long as it does not accumulate in big piles that rot.
(HorseAdvice.com Equine & Horse Advice: Freshly cut grass or hay
and here :P https://www.horseforum.com/horse-heal...s-28895/page2/
I'm confused, there are many different thoughts on this.
I do sometimes cut long grass with scythe and feed it to my mare, but always small quantities, less then half a meal. She eats it in half an hour and I've never had a problem.