Avoiding Laminitis…by Dr Tom Shurlock of British Horse Feeds
There is an increasing understanding of the underlying causes behind laminitis. Currently it is thought that there may be a seasonal hormone dysfunction – possibly induced by an underlying problem such as Cushing’s or IR – which helps explain why only a proportion of horses may succumb, but succumb during spring and autumn when grazing is potentially dangerous.
What we do know, though, is that the swelling and eventual breakdown of the lamellar can be initiated by a number of nutritional cues. High levels of protein, escaping digestion in the small intestine, can be fermented in the hindgut producing toxic end products such as amines and nitrites. High levels of starch and sugars, likewise entering the hindgut, can produce lactic acid which increases the permeability of the hindgut to those toxins (as well as those generated by bacteria dying due to changes in the hindgut ecology). This leads to vascular constriction, inflammatory cues and oxygen depletion, all of which add to lamellar degradation.
Unfortunately for us, spring (and autumn) grass is particularly high in those factors that can initiate laminitis. Protein, and sugars mainly in the form of fructans, although glucose and sucrose is also present, can reach 30% of the dry matter in grass – currently maximum recommendations for non-laminitic horses is about 20% and half that for laminitics – and so there is potential for a massive influx into the hindgut, causing microbial disruption and toxin production.
Traditionally we have just restricted grazing; we can continue to do so, but with certain caveats. Firstly grazing cropped grass is not as sensible as was once thought. The base of the grass leaf is a sugar sink – it’s where the sugars are stored – and so it is far more sensible to let the horse graze on the growing tips, which are low in fructans.
Secondly we need to understand that levels of sugars in grass vary during the day. Basically the sun generates sugar production and these sugars are converted to fibre and growth during the night, as long as the temperature does not drop too low. If it does then more fructans are stored at the leaf base.
So the best time to let a laminitic horse graze is early morning. Glucose production is low and rises during the day, up to mid-afternoon after which it converts to fructans, a process that continues until nightfall and beyond. Late afternoon is not a good time for grazing.
So two steps we can take are to restrict grazing to early morning and access grass that has not been cropped.
A third and more proactive step is to introduce a low sugar fibre alternative. Giving a meal of a well soaked beet based product, such as Speedi-Beet or Fibre-Beet reduces the reliance on grazing but helps maintain hindgut function by supplying a similar fibre profile to grass without the extremes of protein or sugar.
As these products are highly digestible they can replace cereal based diets, further reducing the sugar (starch is merely long chains of sugars) intake by the laminitic horse and so reduce the risk of hindgut dysfunction.
For more information on Fibre-Beet or Speedi-Beet visit: www.britishhorsefeeds.com