Fresh Grass and Colic
We have been alerted to multiple colic cases happening around Auckland and in Victoria, Australia. The incidences of colic in these cases correlated with being turned out on ‘fresh’ pasture and here in NZ it is early spring when the grass is shooting away. (Similar conditions are everywhere and also occur in Autumn).
Immediately call your veterinarian when there are ANY signs of abdominal discomfort or colic. Colic is a life-threatening medical emergency and time is of the essence.
How can ‘fresh’ pasture cause abdominal discomfort/colic? There are many causes of colic in horses – including the following aspects of ‘fresh’ pasture which precipitate various digestive disturbances. Typically: LOW Dry Matter (fibre), sodium and magnesium and HIGH in water, Crude Protein/nitrates and potassium.
We have analysed spring grass in the past that was causing multiple bouts of colic. The Dry Matter was <20%, Nitrogen was really high at 5.5%, CP was extremely high at 35.6%, Nitrates 570ppm, Potassium high at 3.8%, Sodium very low at 0.07%, the DCAD was way too high at 508, Soluble Sugars were only 6.7%. Not surprising this grass caused repeated bouts of colic in the three horses grazing it!
It doesn’t pay to take symptoms like “Loud Gut Noises’ or sloppy manure too lightly.
When such imbalances from either short or lush green grass are exacerbated by a change of season or a high rainfall event, they can affect the horse’s nerve and muscle function, becoming evident not only in the more obvious skeletal muscles causing tightness and hollow posture, and also co-ordination problems in the sacro-iliac region (bunny-hopping, disuniting) but also in the parasympathetic nerves and muscles which operate the entire digestive system.
Disturbances to nerves and muscles that operate the digestive tract interfere with the mechanics of ‘peristalsis’: “the involuntary constriction and relaxation of the smooth muscles of the intestine which create the wave-like movements that propel the contents of the digestive tract forward”.
When ‘peristalsis’ either speeds up or slows down it is playing havoc with ‘gut motility’ – the rate of passage of the contents of the digestive tract. This can result in excess fermentation (Loud Gut Noises that you can hear from several metres away), soft to ‘cow-pat’ manure and diarrhea - and also lead to ‘gaseous’ or ‘spasmodic’ colic.
When peristalsis is inhibited the rate of passage of the ingesta slows right down and even ceases altogether – also resulting in life-threatening colic.
Any change to ‘peristalsis’/‘gut motility’ also CHANGES the internal environment of the ‘soup’ in which the gut flora reside, thereby adversely affecting the composition of the microbiome. Therefore it is preferable to wait until peristalsis has returned to normal functioning before administering pre or pro-biotics.
The lining of the intestinal tract can also become inflamed and compromise absorptive function resulting in leakage of toxic compounds into the bloodstream and the abdominal cavity fluid with subsequent endotoxemia
To Minimise Risk:
If possible, over a week, so it isn’t a sudden change, eliminate the cause (the green grass) and replace with plain grass hay, no lucerne.
If you have no means of doing so, feed as much hay every day as the horse will eat.
Always introduce horses to pasture by starting with 15 minutes/day and increasing gradually.
Make sure your horse is well nourished ‘up’ on all his minerals and add SALT to feeds rather than relying on a salt lick.
Reference: Veterinary Medicine, A textbook of the diseases of cattle, horses, sheep, pigs and goats – Peter D. Constable, Kenneth W Hinchcliff, Stanley H. Done, Walter Gruenberg
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