Let’s talk hindgut and why we need to keep it healthy

The horse is not like other livestock species.  Unlike the cow or goat, the horse is a nonruminant herbivore. This means their stomach has only one compartment like a pig’s or human’s.  But unlike us, the horse’s digestive system is designed to receive small portions of food over long periods of time.  Their digestion works best when grazing for 12 hours or more daily. 

Ingested roughage and grain passes quickly through the stomach and small intestines.  As it travels, glucose, starch, lipids, protein, and oils are processed and absorbed by the body.

Hindgut

Once food has been processed by the foregut (stomach & small intestine), it reaches the hindgut.  The hindgut is really two fermentation units.  The first unit is the cecum.  The cecum can hold 7 – 8 gallons of water and foodstuff and is approximately 4 feet long.  Here, symbiotic microorganisms (bacteria and protozoa) use microbial digestion to break down primarily cell wall carbohydrates, some protein, and some starches. This process (fermentation) requires about 20 – 30% of the horse’s body weight in water.

As the food breaks down even further, it moves into the Large Colon that is about 12 feet long.  Here, fermentation continues, and water, electrolytes, and volatile fatty acids are absorbed.  The microorganisms used for fermentation also synthesize B vitamins that are then absorbed by the colon.

The microorganisms in the hindgut

Hindgut microorganisms do a fantastic job fermenting the horse’s food.  60% to 70% of the energy absorbed by the horse is from volatile fatty acids produced through fermentation in the hindgut.  But these symbiotic microorganisms are a little picky and little changes can cause big issues.

Food sources high in sugar

Starch and glucose are supposed to be digested and absorbed by the foregut.  But rapid consumption of food high in starch and glucose can lead to these food sources reaching the hindgut.  Once in the hindgut, the fermentation process results in an increase in the lactic acid levels within the cecum and colon.  As the pH levels drop, good bacteria begin to die off and bad bacteria have a chance to flourish.   This state is known as hindgut acidosis.  A high concentration of sweet feeds and lush green grass can both contribute to hindgut acidosis. 

Rapid changes to diet

The microorganisms in the hindgut are also food-specific.  When a rapid change in diet occurs, some microbe populations will grow rapidly while others quickly die off.  As microbes die off, they can release toxins that cause the pH level in the hindgut to fluctuate.  Colic and hindgut acidosis can result from this fluctuation.

Hindgut acidosis symptoms

Horses with increased pH of the hindgut may become picky eaters or seem lethargic.  They may also seem off in the hind end.  If untreated, they may develop laminitis, hindgut ulcers, anemia, and/or diarrhea. 

Prevention

The more you can feed a horse like a horse the less likely it is your horse will suffer from hindgut acidosis.  Here are three steps to a healthier horse.

1. Provide your horse with free choice quality forage.  Your horse’s digestive tract works best when forage is slowly eaten over long periods of time. If 24/7 access to roughage is not possible there are still a few things you can do.  Slow feeders and hay bags work great to extend the amount of time it takes your horse to finish a meal.  Feeding 3 – 4 smaller meals throughout the day also helps. 

2. Eliminate or reduce processed feeds high in sugar.  Ever hear the rule ‘shop the outer row of the grocery store’? We know that whole food and unprocessed foods are the best for our bodies, and this goes for our horse’s body as well. Try supplementing their forage with more natural sources of vitamins and protein like split peas and black oil sunflower seeds.

3. Give your horse plenty of turn-out.  Just like horses are designed to eat throughout the day and night, they are also designed to move!  You don’t need a lot of property.  You just need to be strategic.  One way to do this is to design a paddock paradise.  Check out this fantastic website about the concept – Paddock Paradise.

Resources

The following articles and websites were used to study the hindgut and can provide additional information.

“Digestive Anatomy and Physiology of the Horse | Equine Science.” Equine Science, https://www.extension.iastate.edu/equine/blog/dr-peggy-m-auwerda/digestive-anatomy-and-physiology-horse. Accessed 28 Apr. 2021.

PracticalHorseman. “Architecture of the Equine Digestive System – Expert How-to for English Riders.” Expert How-to for English Riders, Expert how-to for English Riders, 1 Nov. 2012, https://practicalhorsemanmag.com/health-archive/architecture-of-the-equine-digestive-system-11756.

“Rules of Feeding: Changing Feeds.” VetZone, https://www.vetzone.com.au/Horses/Articles/Article/tabid/1968/ArticleID/1977/Rules-of-Feeding-Changing-Feeds.aspx#.YInQkrVKjIU. Accessed 28 Apr. 2021.

Staff, Kentucky Equine Research. “The Hindgut: Understanding Its Role in Equine Digestive Health – Kentucky Equine Research.” Kentucky Equine Research, https://www.facebook.com/KentuckyEquineResearch/, 27 Mar. 2019, https://ker.com/equinews/hindgut-understanding-its-role-equine-digestive-health/.

“The Hindgut’s Role in Digestion – Hagyard.” Hagyard – Equine Hospital, Surgery, Vet, Reproduction, Horse Medical | Hagyard Equine Medical Institute, https://www.hagyard.com/the-hindguts-role-in-digestion. Accessed 28 Apr. 2021.