I was going to post this in 2010 - never quite got round to it.......
Did you know that if you ingested enough water it could kill you? And I don't mean by drowning. There was a case in the UK not so long ago. Yet few of us would declare water to be a bad thing, except maybe cats and the odd spotty youth. Many materials, if eaten in sufficient quantity can have harmful effects. For some substances; Yew Tree Seeds, Laburnanum Seeds, Deadly Nightshade (I think the clue is in the name......... ) it doesn't take very much. So the question then is how much is too much?
The reason I mention this is because grass fructans have been getting a lot of bad press largely because of a study published by Dr. Pollitt in 2006. Now don't get me wrong, this isn't out to demonise Pollitt, he is a fine researcher who no doubt seeks to help horses where he can. But so far as I can tell, this particular study broke a few rules (basic stuff we were taught in 'O' level when I was a lass and yes that is practically pre history for those cheeky folk who know me).
The fructans used didn't come from grass and they didn't even resemble grass fructans. And here on earth not all fructans are created equal. The fructans in the experiment were from chickory and these have a simple, mostly linear structure. Grass fructans are more complex and have branching side chains.
It is unlikely that these different structures will be fermented in the same way, with the same speed and the same quick reduction in hind gut pH. I am unaware of any study where the same results have been found with grass fructans.
A very high dose; 3.75kg of the pure chickory fructan was delivered by stomach tube, and unlike the lager louts of Europe, few horses would naturally ingest anything this way. It would take c.43kg of fresh grass to deliver that much fructan (and remember even then it would be a different type of fructan). Grace is a a hoover, and eats far beyond her theoretical capacity but even at her greediest at c.500kg she struggles to put away more than 16kg. Yes I am that sad that I measure everything.
The peak season for pasture associated laminitis is spring, when fructan levels are low.
So from my simple 'O' level point of view, the findings of this research are that if you hook a horse up to a stomach tube, force feed it an unnaturally and ridiculously large amount of the wrong sort of fructan you are going to disrupt hind gut fermentation and give a horse laminitis.
NB - but why would you?