In the first part of this blog series, The Horse’s Manifesto, we talked about the horse’s inherent need for Friends. Here in part two, we are going to cover their need for Forage.
Everything about the horse’s digestive system, from where the food goes in, to where the food comes out, has evolved to continually process vegetation, mostly in the form of cellulose-rich grasses. Although this process takes roughly 36-72 hours, a two-minute pass through the different zones of their digestive system might look like this:
Head and oral cavity
The horse’s keen sense of smell helps them to recognize grasses they prefer from past grazing experiences or ones they desire today. Their lips are mobile, making it easy for them to choose the grasses they wish to pull into their mouth, the starting point for digestion. Their incisors are designed to shear off the stalks of tough grasses and twigs, which their 12-inch long tongue then passes back to their constantly erupting premolars and molars. The horse’s jaw muscles are strong and provide the power to the molars to start grinding the grasses. Only when chewing happens does saliva start to flow into the horse’s mouth from three pairs of salivary glands. The horse produces up to 10 gallons of saliva a day, and its role is two-fold – it contains a buffering agent which helps neutralize stomach acid and an enzyme that starts to break down the plant matter they eat.
The esophagus
Once the grasses are chewed, they start the one-way journey into the rest of the horse’s digestive system; horses cannot vomit, or burp, which can lead to problems when they consume things they shouldn’t. Swallowing is a complex action, and it moves the food from the mouth to the esophagus, a tube designed to take the food to the stomach. Problems can occur here if something becomes lodged that the horse can’t dislodge, i.e. a piece of hard food such as an apple or carrot.
The stomach
Given their large size, the horse’s stomach is relatively small – only about 8-16 quarts – and food stays here for a short period of time. The lower 2/3rds of the horse’s stomach is protected from acid by a shielding layer, and consequently, it functions best when it is almost continuously processing food. Horses produce about 1.5 quarts of stomach acid every hour of the day, but remember, they only produce acid-buffering saliva when they chew. In addition to breaking down the proteins in their food, the acid has another positive purpose: it slows the fermentation of the foods they eat, preventing gas buildup in the stomach of an animal that can’t belch. But if the horse is subjected to periods of fasting, for example when they are fed only 2-3 times a day, this acid can act against the horse, causing stomach ulcers, especially in the unlined top 1/3 of the horse’s stomach. Gastric ulcers are very common in horses subjected to fasting, intensely managed horses, and those who perform sport frequently or at high levels. Undiagnosed or untreated ulcers are a common cause of many problems, such as cribbing, bucking, poor performance potential, and being a 'hard-keeper'.
The small intestine
Leaving the stomach, the food enters the small intestine, where up to 60% of carbohydrate digestion happens; almost all of the vitamins and amino acids from the foods they eat are utilized here too and absorbed along its 70ft length. The small intestine generally processes food in 30-90 minutes, and the slower the passage, the more nutrients are taken from the foods eaten. Constant access to hay or grass ensures that food passes slowly through the small intestine, therefore maximizing the nutrition available to the horse. Feeding ground or pre-chopped forage hastens food’s time through the small intestine, therefore limiting nutrient absorption.
The large intestine
The partially digested food leaves the small intestine, and enters the cecum of the large intestine. The cecum is an oddly shaped part of the large intestine, about 1 ft in diameter and 4 ft long, that acts as the starting fermentation chamber in the digestive process. The fermentation action of billions of bacteria and microbes break down tough plant fibres such as cellulose that we humans are unable to digest. Food stays in the cecum, fermenting, for up to 7 hours.
Next, the food enters the large colon, where nutrients made accessible through fermentation are now absorbed. The large colon is about 12 ft long and 10 inches in diameter and contains a series of oddly shaped pouches designed to effectively digest the fibrous foodstuffs the horse eats naturally.
After passing through the large colon, the material that flows into the small colon has been processed as much as possible by the horse and is now relatively just waste material. The small colon’s last job is to pull out any excess moisture remaining and form the material into the familiar “road apples” every horse owner knows.
Management practices that work for the horse
As we can see, the horse is designed by nature to graze constantly. We can run into problems with the horse when we deny them this very basic need, and subject them to periods of fasting, or feed them things, such as excess grains, they haven't evolved to process. When an animal’s physical needs aren’t met, their emotional needs also suffer; mind and body are linked, and horses who are denied constant access to forage can exhibit many behaviour problems.
Many horse-keeping traditions dictate the horse be confined (more on that in part 3, Freedom, next month!), and subjected to set feedings 2-3 times daily. As you’ve just learned, this is physically and therefore emotionally detrimental to the horse. So how can we meet this primary need, especially when we don’t have access to large pastures? One way is through the use of what are known as slow-feeders – specially designed nets or boxes that hold hay, and restrict the volume of hay they can pull through at one time. Slow feeders slow down how quickly the horse can eat their hay, and thereby provide many of the benefits of grazing.
A simple Google search for slow feeders will result in many pages of both premade designs and how-to plans that are easily made with common items. As with any product, when considering slow feeders there are things to be aware of:
Designs should ensure the horse’s safety above all else. The normal position for feeding is at ground level, and some designs may not be safe to do this with shod horses.
Horse owners need to take into consideration that some designs may cause certain horses frustration. Holes that are too small, and prohibit the horse from readily accessing food may cause stress to some horses. Some horses need help in figuring out how to get the hay out initially.
Designs with netting made of very small diameter rope may pose a risk if horses get the thin strands caught between teeth. Choosing a feeder with webbing or some other material instead of thin rope may decrease the chance of this happening.
Although owners may shudder at the thought of free-feeding their easy keepers, increasing the horse’s exercise is a healthier option than decreasing their amount of food. Switching a portion of their hay to one with a lower nutritional profile will allow them to forage while keeping an eye on their caloric intake. Soaking hay is another way to remove some of the sugars, while still providing the roughage – and many slow feeders designs make this a snap.
Slow feeders are an excellent addition to the lives of horses unable to forage for themselves ad lib. The increased time chewing produces more saliva, which buffers more acid, and the steady volume of food keeps the horse’s GI system working as it should. The many benefits they provide make them a “must have” recommendation to my own clients for meeting the horse’s second “F” need, Forage.
Up next, part 3: Freedom
Missed part one?
Part one: Friends (I coined the term the 3F's, and wrote this series of articles in 2012 for the IAABC's website. When the IAABC redid their website recently, the blog posts were not moved to the new website. You can find the original posts here on the Wayback Machine (internet archive).