Colic can occur at any time, but what are the dangers during warmer months? Andrea Oakes investigates
WE’RE familiar with the risk of impaction colic in winter, when the move to an indoor lifestyle – together with a drier diet, possibly less exercise and often less inclination to drink – can combine to bring a horse’s intestinal movement to a grinding halt.
But colic in horses still occur in summer, when lush grass and sudden management changes can cause abdominal upsets. Since risks from issues such as internal parasites and dental problems are ever-present, vigilance is required year-round to keep the digestive system running smoothly.
One seasonal danger is sand ingestion, which typically occurs before spring grass comes through or later in summer when pasture is poor. A grazing horse may swallow the sandy soil that is pulled up with the grass roots or splashed onto the grassy leaves by heavy rain after a dry spell.
Sand can also be swallowed during sand paddock turnout, usually with hay that is fed from, or falls to, the floor. The gradual accumulation of a large amount in the gut may cause subtle signs, or none at all, but some horses can develop potentially life-threatening sand colic.
IRISH Sport Horse mare Joules was found sweating and exhausted in her stable one morning last autumn, rolling relentlessly in an attempt to relieve pain.
A clinical examination revealed fairly normal gut sounds, but rectal palpation suggested displacement of the colon and the presence of abdominal gas – enough for the attending vet, Chloe Marsden MRCVS, to recommend immediate referral to the Bell Equine hospital. Surgery was required to remove a huge amount of sand from Joules’ large intestine – enough to fill nearly three buckets.
“Most sand colics can be treated medically, with oral laxatives, but not in Joules’ case,” says surgeon Evita Busschers MRCVS. “We suspected an impaction, based on our clinical examination findings. A radiograph [X-ray] of the abdomen can confirm a more specific diagnosis of sand colic, but she was in too much discomfort to X-ray. Exploratory surgery was the only option.”
While a small amount of ingested sand may pass harmlessly through a horse’s system, if swallowed in larger quantities, it sinks like a sludgy sediment to the bottom of the colon. Its abrasive nature can then irritate the delicate gut wall and cause a colitis-type inflammation or, as with Joules, it can “silt up” the narrower parts of the colon – typically the pelvic flexure.
“The process can take weeks or even months, causing partial or total blockage,” explains Evita. “Food can’t move around easily and gas builds up, putting the bowel at risk of a twist or torsion.
“The biggest risk with surgery, aside from the general anaesthetic, is rupture of the colon,” she says, describing how the bowel must be lifted out through an incision along the horse’s abdomen and onto a tray. “A colon full of sand is so heavy. Sadly, the chances of a catastrophic tear are quite high.
“Once the colon has been manoeuvred and opened, the sand is flushed out with a large volume of water using a surgical hose pipe. The gut is then sutured, the area is rinsed to reduce the chance of abdominal contamination and the colon is replaced.
“The interior lining of the bowel renews itself within five to seven days, so any abrasion usually heals quickly once the inflammatory component – in this case the sand – is removed,” adds Evita. “Depending on how much sand we’ve been able to remove, we may feed psyllium [a laxative] for some time afterwards to encourage any remainder to pass out with the droppings.”
ON HOME TURF
SIGNS of sand accumulation include chronic diarrhoea, weight loss or a milder colic due to low-grade, grumbling pain, but there may be few clues.
“Looking back, Joules was napping in an unusual way at a cross-country schooling session the week before, and her coat was a bit dull,” says her owner, Jordan Harvey. “But she was otherwise well.
“At the start of summer, I had moved her to a new yard, from clay soil onto sandy soil. She was turned out every day, but there was less grass available.”
During a prolonged recovery, Joules suffered nasogastric reflux – a pooling of fluids in the stomach – requiring removal every three hours by nasogastric tube. A secondary gastric impaction then had to be broken down by lavage with further fluids, including Coca-Cola, and once back at home she needed treatment for an infection at the surgical site.
“Gradually, the wound healed and she became stronger and healthier,” says Jordan, who has moved Joules back to the original yard and hopes to jump her again soon. “I had no idea she had eaten so much sand. I’m so grateful to my own vet and to the hospital team; without it all coming together, she might not have pulled through.”
Could it be sand?
“THE old test for sand in the digestive system involved mixing droppings with water in a suspended plastic glove”, says Karen Coumbe MRCVS. “The theory is that, over time, any sand present will sink down into the fingers, but that is rarely convincing.
“Researchers in Finland recently published studies that described the test as “moderately accurate”, but noted that while a positive test is usually correct, it does not reveal the severity of the condition. Neither does a negative result rule out the problem. The glove test may be a useful diagnostic tool if you are worried about horses grazing on very sandy soil, but it is far better to consult your vet, who may recommend X-rays, ultrasound and rectal examination to provide a clearer picture.
“Horses in Finland reportedly suffer from sand colic, highlighting that the condition is not confined to hot, dusty environments. Another recent piece of research from there – a retrospective study of more than 1,000 cases – revealed that daily nasogastric tubing with psyllium and/or magnesium sulphate (Epsom salts) for three to seven days is more effective for removing large accumulations of sand from the colon than feeding psyllium for at least 10 days.
“Medical management with oral laxatives is the preferred treatment in all but the worst cases, where fluids tend to wash over the accumulated sand rather than flushing it through the system. Horses at high risk or with a history of sand-eating may benefit from a psyllium feed supplement. If turnout in a sand paddock or on sparse, unhealthy pasture is unavoidable, feed hay from a low-level manger rather than from the floor.”
Common culprits for summer colics
SUMMER digestive disorders are often down to one of three factors…
A flush of grass growth can trigger a reaction in the gut and create gassy colic, which can cause the colon to displace or, even worse, to twist – a particular problem with mares who have recently foaled and have extra space in the abdomen.
Impaction colic is not just a winter worry, so try to avoid dietary disturbances such as stabling ponies on straw bedding for a week at camp, or adding electrolytes to drinking water without realising that the horse does not like the taste.
A potential killer, and most common between April and July, equine grass sickness (EGS) is a degenerative disease of the nervous system that results in impaired motility of the gut.
Modern de-wormers have reduced colic risk, but anthelmintic resistance is increasing. Encysted small redworm – also called strongyles or cyathostomins – are a particular threat, lying dormant in the gut lining before emerging en masse to cause diarrhoea, colic and often death.
Targeted de-worming is a must and poo-picking, however tedious, is beneficial.
This feature is also available to read in Horse & Hound magazine, on sale Thursday 3 June 2021
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