I'm not entirely convinced that anyone has yet actually pin pointed what the problem IS with grass
That's because we don't have a clue about much to do with laminitis as yet. However, here are my thoughts for what they're worth...
Typical pasture has been fertilised at least some and often a lot. The result is that the dominant species is rye grass. Overall the pasture will be high in sugar and low in fibre. There is also typically a lot of productivity so the horse has to be kept on quite a small area so as not to get too many calories. The result is a high sugar, low fibre diet and not much exercise as the horse has all it can eat right in front of its nose. Basically this is couch potatoe syndrome.
However, the problem is clearly not as simple as just fibre/sugar content. The mineral content of the pasture will have some impact as well. I've got one yard where the molybdenum levels in the soil are really high and all the horses are sick as a result. And I've got another yard (half way up a mountain) where the pasture is acidic and all the minerals have leached out - resulting in multiple deficiencies (seleniun, copper, cobalt, zinc, magnesium being the worst ones). These kind of mineral imbalances can be a major problem for horses and even the most ideal looking pasture can turn out to be badly balanced.
would you still recommend that people are better to turn their horses out at night on grass rather than the day?
Yes. The sugar levels are lower at night and even if you don't know what has caused the insulin resistance (assuming that's the problem - not all cases are insulin resistant), that's going to be less likely to trigger an attack. I've seen lots of cases where horses do better when turned out at night rather than during the day.
Are horses in general better kept on hay/haylage and without access, or minimal access to grass, whether they are IR/lami/etc or not?
In general, I'd say yes. It would seem that dried forage is less of a problem than fresh for most horses. Is that because the sugar levels are lower in hay/haylage? I'm not totally sure. But then I've seen the reverse situation - which may be because the dried forage has come from somewhere that's got less good mineral balance than the available grass. So as usual, it's not simple.
As for Kathy Watts and safergrass.org, please be careful here. Firstly, this is a US based site and the grass species over there are quite different from, say, the UK. For example, I gather fescues are a major problem in the US, whereas the species of fescues we have in the UK generally seem quite good for horses. I also, personally, think that Kathy's standard of research is so low I'd not even bother reading anything of hers any more - but that's just my opinion as a scientist
I also liked the nutritionist's comments about how long it took to cut 1kg of grass with scissors - a very good way of looking at it (if rather painful to actually do!)
One idea, wich i'll be trying this year, is seeding the field with starch building grass species instead of fructan ones
I often hear people saying that they want to plough up and reseed with 'better' grasses. There are two problems with this. The first is that we still don't have a clue what a healthy 'wild' horse is supposed to eat (mainly because there aren't any truly wild horses left to study - I suspect wild zebras are likely to be the best study). Given that, how can we decide which type of grass is going to be good?
But the more serious problem is that pasture isn't like some flower bed where you can plant a few seeds and then weed out the weeds so your chosen plants prosper. Unless you plan to weed your entire field by hand, you're going to have a dynamic ecosystem where survival of the fittest rules will be in play. The pasture you have now (unless it's been recently reseeded) will consist of the mix of plants best adapted to survive in the prevailing conditions (soil type and acidity, rainfall, temperature, aspect, etc.). If you reseed with different plants, you are pretty much guaranteed to be seeding plants that are less capable of surviving. All that will happen is that the previous plants will have seed in the ground and seed will come in from surrounding areas and the plants that are best adapted (i.e. what was there before) will happily out compete your prefered plants. Typically within 1-2 years you'll find that your chosen plants are doing badly and within 3-4 you'll be pretty much right back where you started. The best way (and pretty much the only effective one) to change a pasture is to change the prevailing conditions. And the biggest problem there (at least in most UK fields anyway) is fertility. Once artificial fertilisers have been applied, you can't easily get the fertility down again - so the kinds of grasses that are suggested as possibly better for horses won't survive (rye grass will outcompete just about anything in a high fertility pasture). The best way to do it is to heavily graze and cut - but you're looking at 20-30 years to get the fertility down to sensible levels. Alternatively you can turf-strip but in the UK, that requires a mineral extraction license.
After all all the species of "corn" are just grass that's been bred with a view to producing larger seed heads
Yes, but there's a difference between feeding leafage and seed heads. For example, oat straw is higher in fibre and lower in sugar than grass hay, but in comparison oat seeds are quite high in sugar/starch and much lower in fibre.
mmm, if sugars/fructans are really to blame, then as far as i know, any stress to the plant makes it build them up! lack of nutrition (fertilizer) is also stressful, but maybe someone who knows about agriculture can correct me.
Sadly this is yet more myth being put about by people who really don't know what they're doing. Firstly, lets cut the fructans out of the argument as the numbers totally fail to add up. So we're talking here about what brings grass sugar levels up in general. There is actually NO evidence whatsoever that lack of fertiliser is 'stressful' and causes sugar levels to rise. The issue here is that fertility drops VERY slowly (see my comments about 20-30 year timescales above). If you stop fertilising, you won't see any appreciable difference in fertility for several years. As the fertility drops, species that are better at coping at slightly lower fertility levels will gradually out-compete the species that do best at higher fertility levels. At any point in that cycle, there will be a few plants that are struggling a bit and might be described as 'stressed' (although there's no evidence that this raises sugar levels anyway), but there'll also be some plants doing a bit better. As the process is very slow it's a very small effect. Now Kathy Watts and her cohorts tell us that this is a big problem and we should apply fertiliser. If we do that, the fertility jumps upwards very suddenly. Now suddenly we have a pasture full of plants best suited to lower fertility but the fertility is too high for them. The balance of plant species present is going to change quite rapidly (perhaps over a few weeks) potentially resulting in far more stressed plants than in the previous case.
So if you accept that grass suffering fertility stress is higher in sugar and therefore bad for horses with laminitis (which is a BIG assumption given the available evidence), then the absolute WORST thing you can do is apply fertiliser because that's going to create a rapid change and therefore higher levels of stress than just leaving things alone.
Interestingly, I see quite a few laminitis cases caused by putting horses on recently fertilised pasture - although my suspicion is that it's nothing to do with 'stressed' grass and everything to do with the change in mineral availability caused by putting high availability nitrogen, potassium and phosphate onto pasture that are already excessively high in these minerals.
What's so frustrating for me is that these kinds of myths about the links between pasture and laminitis continue to be propagated by a lot of people who really should know better. The problem of course is that there's no-one in the laminitis research area with any detailed knowledge of grassland ecology. And the people who have appointed themselves as the experts in this field are often amateurs who really don't have sufficient background to know what they're doing.
We have had our soil tested,
Not much point in that as minerals can be present in the soil in forms that plants can't access. So you might see a nice healthy copper level in the soil, but the grass is low in it. I always recommend testing forage rather than soil as it gives a much clearer picture.
I was once told by my vet that weeds actually contain more sugars than grass but I'm not sure what evidence he was basing that on.
Neither am I
This is exactly what I'm talking about above. Firstly, you have to define 'weeds'. Is clover a weed or an agricultural pasture species introduced to increase protein content of the pasture? Is a fescue a weed or a grass better adapted to lower fertility levels? Technically a weed is just an 'undesirable' plant - but that means it's dependent on context. A weed for a dairy farmer may well be exactly what we want our horses to be eating! So basically weeds can be all sorts of different plants and the sugar content is going to vary wildly depending on which plant you're looking at. The trouble is that people act on this kind of misinformation and often end up doing completely the wrong thing. One of my clients used broadleaf herbicide to kill all the 'weeds' in her field so that it would be better for her horse - she followed the manufacturer's advice on the period to exclude her horse and still manage to poison her to the point where she had a massive laminitis attack (she'd been absolutely fine before).
I am constantly horrified by how much misinformation is given out by vets and other horse experts - much of which if acted upon seems to make the laminitis problem far worse.