Self-Feed Regulation

Sep 17

9/17/21

“Can horses self regulate their feed intake?”

TRUE OR FALSE - Healthy adult horses have a physiological mechanism which enables them to self regulate intake of hay and grain. This mechanism serves as an internal "shut-off" system when they are either full or have reached optimal nutrient status within the body.

Appetite, eating and satiety involve hormones, the central nervous system and sensory cues (palatability/taste, texture, etc.). An integration of these things should tell us when we're full or hungry. While this is described and understood reasonably well in humans, how this system operates is poorly defined in horses.

They have the same hormones of satiety and hunger that humans have, but whether they behave the same has yet to be fully understood. Yet, based on equine eating habits, we can draw some conclusions.

When given a buffet of a highly tasty opportunity (ie. Grain), many horses will overeat in excess - sometimes to the point of sickness or death. Remember the story you heard about the pony getting out of its stall in the night and eating all the grain, then foundering?... Grain tastes good... no self regulating capability here or shut off mechanism happening with the horse that gets into the grain bag. Will some stop after eating a non-dangerous amount? Sure... but many horses will still self select grain intake to the point of foundering.

Palatability overrides any satiation signals in this case. The unfortunate part is that excess grains that make it to the hindgut are dangerous for the health of the horse. Yet... overconsumption still occurs.

What about forage... horses in the wild utilize energy from forage as they spend their day roaming. The quality or forage for wild horses is lower than that of the domesticated horse (usually) and we hand the domesticated horse lush forage to consume. This may be why wild horses don't have the extent of obesity issues that the domesticated horse has, and why the horse doesn't have a good "shut off" signal. They've evolved as an animal who's job is to eat and keep eating small fibrous meals most of the day. So, who needs a shut off mechanism when you need that energy to stay alive and survive the natural elements? Remember the domesticated horse comes from wild horses... the gi tract has been evolving for millions of years and is the same in both horses.

Back to forage, a horse will consume forage to their heart's content. When we give them quality forage and/or pasture many will even consume this to the point of obesity. And while it is ideal to mimic the natural diet of the horse (wild horses grazing 14-16 hours a day), especially since the GI tract lends to this eating pattern (small stomach that empties quickly and continuously secretes acid), this makes the domesticated horse obese because they don't have the "I'm full of nutrients and energy (calories) and should stop eating" signal. There are systems in the body which regulate internal energy balance, but the horse is not prompted by any such mechanism to stop when they've met or exceeded energy requirements.

So here is my position... when we think about the terms "self regulation" and "shut off mechanism" as I used in my post, this really isn't happening. Sure, some horses still maintain ideal condition when they have a nonstop buffet of forage, kind of like our skinny friends who eat everything all day and stay slim. Damn metabolism...

And just to clarify, when I say self regulation, I'm referring to intake that meets requirements and doesn't exceed those - in terms of energy (calories) especially. When I say shut off mechanism for hay or grain intake, I'm saying there is a signal that results in cessation of eating when the horse consumed "enough".

So is there an identified shut off signal in the horse? No.

Does the horse take breaks in eating during the day still? Yes.

Why does this happen? Boredom, rest periods, herd dynamics, feeling of fullness? Hard to say definitively.

But again, when I consider the natural eating habits of the horse, and based on the number of obese horses I work with, I will say horses are very poor at self regulating and don't have a "stop" signal.

To make a long post longer, I say FALSE. While some may disagree, I put far too many horses on diets to believe a horse is good at self regulating their intake based on their actual energy and nutrient needs.