We are delighted that, after the very helpful and informative talk on Winter Management that Chris Lehrbach BVMS MVM Cert ES (Orth) MRCVS gave at our open evening in September, he and his team have agreed to write occasional articles for us on topical health issues.
At present a number of our equestrian customers have mentioned problems with colic and so here is the advice Chapelfields Veterinary Partnership have kindly provided.
Why do lots of horses, ponies and donkeys seem to get bouts of colic more commonly at this time of year?
There are a number of reasons that the incidence of colic increases in the autumn and most are related to changes in management and diet as we move from summer to winter. Most equines in the Norfolk and Suffolk areas spend substantial amounts of time out at grass during the summer, living on a feed with very high water content, creating a relatively laxative diet. Some animals drink very little water in the summer as they can get so much from a diet high in grass. As a result, the time taken for food material to pass through the gut is relatively short and the consistency of dropping is relatively soft.
When the weather turns and the ground starts to get soft and muddy, owners shorten the time spent in the paddocks. Even relatively bare fields still have considerable quantities of grass; it simply gets eaten straight away keeping the sward very short and giving the appearance that there is not a lot to eat.
Quite often the time stabled increases quite suddenly, for example if an autumn storms appears a horse may go from spending 8 hours outside, to being totally stabled in one weekend.
Once stabled the animal will be eating mainly hay or haylage, both of which have a much greater fibre content and much lower moisture content. Also, many horses will eat their bedding especially if it is made of barley straw. Unfortunately, a period of adaptation is needed by the gut to digest this much drier diet, usually about two weeks in total. Firstly, the level of fluid secretion has to be increased and secondly the types and quantities of bacteria that live in the gut have to change according to the content of the new diet. The results of a sudden change are a slower rate of food passage, potentially resulting in a blockage called an impaction, increased gas production and irregular and in-coordinated gut movement. Gas and food build up distends the bowel causing pain and in-coordinated gut activity results in cramp, both of which are fundamental signs associated with colic. Gas build up can also cause gut to float up and flop into an abnormal position causing a bowel displacement, another, potentially surgical cause of colic.
The key to minimising the incidence of autumn colic is make any change to the diet or general management gradually, over a two week period, ensuring that any new feed is introduced gradually. Some owners will also provide probiotics during this time to help maintain gut bacteria during the change. Continued access to grazing, even for only short periods on relatively bare paddocks can allow a more gradual transition.
A relatively uncommon but very serious cause of colic in the autumn is grass sickness, a usually fatal form of toxaemia. Grass sickness is believed to be caused by ingestion of a toxin produced, under certain environmental conditions, on the pasture, causing death of nerve cells in the gut. Once this happens the animal’s entire gut becomes paralysed permanently. With no ability to swallow or drink the animal would die within a few days and affected animals are normally euthanased on humane grounds. Very occasionally patients survive but they are a tiny minority. Although there is no treatment available at present, it is hoped that there might be a way of producing a vaccine in the not too distant future.
From an owner’s perspective the only ways to reduce the risk of grass sickness is to avoid grazing paddocks where cases have previously occurred, particularly in the spring and autumn and particularly if a dry spell is suddenly followed by some inclement weather. The recent movement of soil or digging on a pasture such as placing of drains is also believed to un-earth the causative toxin producing bacteria. It appears from research that animals fed supplementary feed while out at grass at this time of year are also slightly less at risk of developing grass sickness.
Questions relating to the above topic can be directed to the author at Chapelfield Veterinary Partnership Ltd.
Chapelfield Veterinary Partnership Ltd
Norfolk NR15 2PD
Tel: 01508 530686