It’s Christmas day tomorrow; a day of indulgence when we typically eat several times as many calories as we need! Providing we balance this indulgence out over the week, it is not a problem. For horses, however, days of indulgence can be much more of a problem.
Horses have more ‘delicate’ digestive tracts than humans, probably because they have evolved to thrive on a specific type of diet, whereas humans have evolved to thrive on a very varied diet.
The main two indulgences that can cause serious problems to horses are eating too much starchy grain or eating too much fructan-rich grass. Both can cause laminitis, and the former (and sometimes, the latter) can cause colic.
Starch in small quantities is well digested by horses in their small intestine, and can be a useful source of calories for hard working horses. Larger quantities of starch, however, can overload the digestive capacity of the horse’s small intestine, causing undigested starch to flow into the hindgut (large intestine). Horses produce only small amounts of the enzyme that digests starch. Undigested starch flowing into the hindgut is a food source for acid-producing bacteria, which flourish given large amounts of starch. These bacteria can flourish so extensively that they cause a hindgut acidosis, which can lead to unthriftiness, poor performance, and in acute cases, colic, laminitis and even death.
Fructans are also perfectly safe in small quantities, and even have a beneficial effect on the horse’s digestive tract in controlled amounts. Fructans are the main storage carbohydrate in UK grass (along with sucrose, a sugar) and amounts in grass can vary widely. Fructans are not sugars, but are sugar-like compounds that are digested by the horse completely differently to sugars. Fructans cannot be broken down and digested by digestive enzymes, but are instead broken down by bacteria in the gut. If eaten in large quantities over short periods, like starch they cause an extensive flourishing of acid-producing bacteria, which can cause laminitis in susceptible horses and ponies.
Dietary indulgences of any sort are unhealthy for horses because their diets should be consistent and always changed gradually, not suddenly. The main reason for this consistency is that they rely on a huge population of beneficial bacteria, fungi and protozoa, which break down fibre, releasing nutrients for absorption, and these microbes rely on a consistent food source for their health. Healthy gut bugs are necessary for a healthy horse!
Horses should have all their feed, including forage – and even pasture grass – changed gradually. Weekly bran mashes, one-off (large) scoops of oats or coarse mix as a treat and all-day turnout on new grass are all unhealthy indulgences for horses.
Have a very Happy Christmas, and enjoy a bit of indulgence whilst limiting your horse’s indulgence to an extra carrot or two.