Thursday, 5 June 2014

Why not all grass is created equal - and why horses can have problems with grazing

I posted a link on Facebook the other day to this fascinating research which has been published by Bangor University.
The research was flagged up in an article which is online here (you may need to register to read it) and one of the encouraging aspects is the acknowledgement that UK grass has the potential to be very dangerous for horses, particularly in spring and autumn.  

Of course we all knew that already but its great to see an article aimed at farmers pointing out that horses very often simply can't tolerate the high sugar levels in our grazing.

The research project was particularly interesting for me because it:

"set out to analyse sugar content of old pasture species from a hill farm in North Wales and compare the sugar levels with more modern types of grass such as perennial rye".

Why is this interesting? Simply because its an issue we see here all the time.

Horses come to Rockley and can graze our grass very safely. We don't turn them out 24/7 because its essential for their feet that they spend time on the tracks but most horses cope extremely well with grazing here, even those who have been diagnosed with metabolic problems or who can only tolerate very limited - or no - grazing back home.
Like the hill farm in the study, our fields have a wide range of different plants and grasses in them and horses also have access to the hedges and some wooded areas while they are turned out - both on the tracks and in the fields. 
A study of plants undertaken by the National Park at Rockley some years ago found 38 different herbs and grasses in one field alone and  - interestingly - noted that the scrubby, apparently "low value" grazing areas were favourite areas for the ponies who were kept here then.

By contrast, many modern fields have a very limited number of grasses and so the biodiversity available to grazing horses is restricted. This can be a problem because horses, unlike cattle, have evolved to thrive on high fibre, low sugar diets and love to forage on shrubs and other plants rather than graze exclusively. Ryegrass is a favourite in modern farming because its good for producing beef and dairy cattle, but horses need a very different diet. 
For horses, the most dangerous part about ryegrass is the sugar levels and this is what the study was aiming to quantify. When they compared the fructose contents of the ryegrass vs the hill grasses the difference was shocking. 

"The new variety [of perennial ryegrass] is the highest with a 332mg/g fructose content in comparison to 0.52mg/g in Meadow Fescue".

Yep, you read that right - modern ryegrass can be 600 times higher in fructose than old pasture species.

So its pretty clear that horses who can safely graze old permanent pasture can quickly develop serious problems on even tiny amounts of modern leys, especially as they love the sweet, sugary taste of ryegrass.  A double-whammy is that short, sweet grass often contains not just too much sugar but not enough fibre - exactly what the horse does not need. 

This can lead to obvious, immediate veterinary emergencies like colic and laminitis but also slower, insidious damage which results from consistently high levels of sugar in the diet - metabolic problems like PPID (cushings) and insulin resistance which take longer to develop but are just as damaging. 
Its fantastic that research like this has been done because for too long horses and their owners have been suffering from the consequences of inappropriate grazing but without having many solutions or alternatives, especially if grazing needs to be restricted. 
Now we have a real chance to not only develop better management systems for our horses but also use better grasses and grazing so that they can be more safely turned out and have the sorts of lifestyles which they - and we - love. 


Diana said...

Was interested though that their results showed fructose levels lowest in the middle of the day. My previously held belief (I think from was that daylight causes the grasses etc to make fructose and then at night (if it is warm enough) the plant grows and thus uses up the fructose, meaning that the safest time to graze is early morning. This seems to make more sense to me and I would love to know their explanation for what they seem to have found.

Nic Barker said...

Well 2 points to note, one that they were measuring fructose, not fructans levels - so only one of the sugars.

Secondly the article states quite clearly that the finding of low fructose at 1-2pm is contrary to earlier studies(!) maybe should not be completely relied on...

Anonymous said...

Just out of interest - we graze on old pasture, there is some rye grass but other species too (of which I can only recognise fog grass and Meadow Fescue) but we also have a new grass which has appeared since the wet weather - plicate sweet grass! Have you ever come across this in your grazing and is it one which is suitable for natives? We have three ponies, one with cushings and all are native. We have never had laminitus and one pony is barefoot .

Nic Barker said...

Species makes a difference but it seems to be variety - and the amount of total ryegrass - which is just as important. The article I've referenced didn't give sugar levels for each species, however, which would have been useful.