Does an Hour Make a Difference?
Dr. Andrew Hoffman
On April 4, we will turn our clocks ahead one hour, beginning daylight saving time. Many people wonder what effect the time change has on horses and their feeding schedule. The answer is: very little. (It has a greater effect on us if we forget to reset our alarm clocks!)
However, it does draw our attention to the potential impact of sudden changes in feeding times.
Veterinarians are constantly harping on the concept of "consistent feeding." They will invariably ask you, in the event of colic, "Has anything changed?" Why are they so vigilant about this point?
Firstly, horses have not evolved or adapted in any way to accommodate twice per day ("bolus") feeding. In nature, horses graze continuously on large prairies. Yet, bolus feeding is now universal in our stables, and the horse's body responds in ways that are not natural. There is an extreme, albeit invisible, gearing up process after each bolus feeding, morning and night.
After the horse eats grain and hay in the morning, it secretes about 7 to 10 gallons of fluid into the stomach and upper small intestine to digest carbohydrates, fats and proteins. This causes the body to teeter on a kind of internal dehydration.
The fibrous stuff, carried by this new "river of fluids," largely bypasses the small intestine to enter the large intestine. In the large intestine, some of the fluids are reabsorbed, rescuing the horse from actual dehydration. Yet, the huge secretion of fluids spawned by bolus feeding, temporarily has to draw from somewhere – the bloodstream in fact is the major source. This fluid shift triggers a vast number of hormonal events to counteract the sense of dehydration, such as those that occur with sweating. A well-timed hormonal response, independent of daylight and time, is set into motion, like a pendulum to deal with boluses of feedstuff – whether coming twice or three times a day. The fluid shift (dehydration – re-hydration) cycle is complete in less than 6 hours, but some of the hormonal triggers lag behind, and are still active during the next feeding.
In comes the end of daylight saving time. You change your clock ahead an hour and surprise your horse by coming in at a different time. More than likely, the fluid/hormonal 'pendulum' has swung back into place, and your horse's body is ready to accept the new load. Exceptions might occur in a horse heavy in work, sweating profusely, and consuming large quantities of grain.
So the good news is that there is little evidence that your horse will be ill-prepared to deal with a one hour shift – it won't hurt to make their shift gradual, but this may be overkill. The problem lies with more irregular feedings that change from one day to the next by 2 to 4 hours, or feedings that are too close together. The fluid shifts necessary to deal with these irregularities exacerbate fluid losses due to sweating and heat challenges. In the event not enough water is consumed, the fluid absorbed from the large intestine may outstrip its softening function, culminating in an impaction.
In general, to buffer against any anticipated change in feeding, it is a good idea to assure excellent hydration. To do so, provide fresh, soft, low-mineral, water at all times. Automated waterers encourage greater intake. Add loose salt to the grain each day (about 100 grams to 5 tablespoons of regular table salt, divided into 2 feedings) to increase water intake. This could be the most important supplement you give your horse! Grain, hay and salt blocks do not provide sufficient salt intake for a working horse. Another way to buffer against large shifts in fluid balance is increased frequency of feeding. Bran mashing four to five times a week offers another opportunity to encourage water and salt intake. Add regular salt, not Epsom salts. The latter encourages water to stay in the gut, and the horse may not be drinking enough to satisfy the gut and the tissue demand for water, resulting in tissue dehydration. In essence, don't mess around with Mother Nature.
So the only real concern about the start of daylight saving time is that your barn help arrives on time. Although an hour probably won't make a difference, it may be worth reflecting at this time on why regular feedings are key, and on some simple ways to buffer the effects of bolus feeding and dehydration.