The Links Between Pasture and Spring Colic in Horses

 

 

Horse Anatomy – the Digestive System

 

• Horses begin digestion of their feed and forage by chewing and end by passing manure.

 

• At the input end, it starts in their mouth. Teeth break the food apart, and your horse’s saliva starts to break down the food further.

 

• Then, the food travels through the pharynx into the esophagus. The pharynx is where the digestive system and the respiratory system overlap. The soft palate is a one-way valve to prevent food from entering the lungs or returning to the mouth.

 

• Then, the esophagus, a long muscular tube, squeezes the food toward the stomach.

 

The horse’s foregut

 

• The foregut has two parts – the stomach and the small intestine. Hydrochloric acid and enzymes in the stomach further digest the food before sending it to the small intestine, where most nutrients pass from the food into your horse’s body.

 

The horse’s hindgut

 

• The hindgut is where the magic – and danger – happens. The hindgut is the cecum, the large colon, the small colon, and the rectum.

 

• The cecum is a blind sac, meaning the entrance and exit are the same. It’s also full of microbes that digest the food that your horse’s body can’t.

 

• The large and small colons reabsorb water and collect waste materials. Think of this as the birthplace of manure. Microbes ferment the foodstuff and need a certain balance to avoid developing diarrhea, impactions, and pH changes from microbial action.

 

• The last stops are the rectum and anus, which collect and deposit fecal balls for you to round up.

 

 

Fermentation in the hindgut

 

• By the time forage and feeds enter the hindgut, it’s mostly fiber. While in the cecum, there is some fermentation by the microbes, which continues in the large colon.

 

• Those little bugs change the fiber into energy and nutrients. Microbes convert fiber into volatile fatty acids (VFAs) that your horse uses as energy. Lactic acid is another microbial product, which your horse changes into glucose as another energy source.

 

• Nutrients released include some B vitamins and amino acids.

 

When fermentation goes wrong

 

• The most populous bacteria in the hindgut are the lactic acid bacteria, accounting for most of the energy made. Other microbes produce methane, a gas that results in farting. Both of these can go askew.

 

• If there are too many sugars and starches in the hindgut, the acids and by-products of fermentation change the pH level of the hindgut. This imbalance will kill many of the microbes, releasing endotoxins after death. There’s also more gas than usual.

 

• The changing pH will also make the intestinal walls permeable, and those endotoxins can creep into the bloodstream and end up in the hooves, contributing to laminitis. Meanwhile, excessive gas can contribute to colic.

 

• There’s also a condition called hindgut acidosis, where the digestive system remains at a changed pH, increasing the risks of colic and such.

 

 

How Spring Pasture Can Trigger Colic

 

• Spring grass has one focus – to grow and reproduce. To do so, the grass must use sugar and starch as fuel to grow tall and lush and produce seeds for future generations. Pasture grass, especially spring and fall pasture grass, is much higher in sugars and starches to make this happen.

 

How sugars and starches start a colic chain reaction

 

• As spring perks up the pastures, it’s also a diet change for your horse. Turnout is likely longer, and all those sugars and starches are much more delicious than dried-out hay forage.

 

• Now you have the perfect colic storm – more time on grass, a different diet, and higher concentrations of sugary grass.

 

• Your horse’s hindgut becomes a pH-changing, gas-making machine.

 

• Aside from the laminitis and subsequent founder risks, that extra gas can create discomfort and bloating and may even move organs out of position and into a twist, sometimes called a torsion. The additional gas can also pressure organs and restrict blood flow in some areas.

 

Common Signs of Gas Colic in Spring

 

• Colic is a general term for abdominal pain in horses, and there are many causes, such as impactions, twists, and gas colics. In spring, it’s mostly the gas variety to worry about.

 

• Early intervention is warranted to relieve your horse’s pain. Colic and laminitis often come hand-in-hand in the spring, may look like each other, and may happen simultaneously.

 

• Any strange behaviors or eating habits signal to you that something is wrong. But horses are not always prominent, and their vital signs give you further clues.

 

 

Vital signs

 

• Your horse’s resting temperature, pulse, and respirations (TPR) are the baseline vital signs you need to know. By checking these signs, they can give you excellent insights into how your horse is feeling.

 

• Most horses will have an increased pulse and respiratory rate when they have pain.

 

• An increase in temperature may result from pain, fever, or overheating.

 

• Or, your horse has just been in the sun, had some shenanigans with buddies, or returned from exercising. Context matters, so if you find some vital signs that are not normal, look for other clues.

 

Your horse’s gums

 

• Gums provide insight into your horse’s hydration status, as well as circulatory and respiratory health.

 

• Ideally, you see pale pink gums that are slippery or wet. Dry, sticky gums indicate dehydration, and red, blue, purple, or white gums mean trouble and should always warrant a call to your vet. The color indicates respiratory health and how well your horse can deliver oxygen to their bodies.

 

• The capillary refill time, where you squish the gums with your thumb and then count the seconds until the color returns, is another value to track and should be 2 seconds.

 

Read more about vital signs here and your horse’s gums here.

 

Gums should be pale pink!

 

Digital pulses

 

• Each leg has their own pulse, and it’s not a measure of their heart rate. The digital pulse, measured under each fetlock on both the inside and outside of the leg, alerts you to increasing pressure and pain in the hoof.

• A normal, healthy hoof will have a non-existent or faint pulse. As pressure increases in the hoof due to injury, abscess, bruising, laminitis, hot nails, or any other reason, that pulse will increase, often to the point of bounding.

• A strong digital pulse is one of the best reasons to call your vet and can indicate laminitis, especially in the spring.

 

Read more about digital pulses here.

 

Behaviors that signal colic

 

• Because horses are unique individuals and colic is a broad term meaning abdominal pain, the list of colic signs in horses is long and varied. You might see:

Mild Signs of colic:

•Pawing at the ground

•Looking at or biting at the flank

•Restlessness or repeatedly lying down and getting up

•Lack of interest in food

•Reduced or absent manure production

•Slight bloating or distended belly

 

Moderate Signs:

•Kicking at the belly

•Lying down and rolling frequently

•Stretching out as if to urinate

•Heavy sweating

•Increased heart rate (over 50 beats per minute)

•Reduced, increased, or abnormal gut sounds

 

Severe Signs (Emergency Situation):

•Violent rolling or thrashing

•Profuse sweating

•Rapid or labored breathing

•Extreme bloating

•Weakness or collapse

•Gums that are pale, dark red, blue, or purple

 

• Many horses have subtle “tells” that also give away their pain, such as the flehmen response or strange lips wiggling. Others might urinate frequently in small amounts to relieve pressure. Careful observation, over time, gives you the eagle eyes to spot well-hidden signs.

 

Can you tell the difference between a colic roll and an itchy roll?

 

 

When to call your vet

 

• A direct relationship exists between waiting to call the vet and a much larger vet bill, especially during high-risk times like grazing on spring and fall pastures.

 

• Calling your vet early results in:

 

• • Less pain for your horse
  • Smaller vet bill
  • Peace of mind
  • Prevention of complications like stall rest, surgery, founder, and more.

 

• As a side note, always chat with your horse’s vet about giving medications. For some cases of colic, your on-hand pain meds will mask signs that are needed for a proper diagnosis. In other cases, you may not have the unique anti-spasmodic meds that can help different types of colic.

 

Treatments for Gas Colic in the Spring

 

• Treating gas colic involves pain relief, easing the gas build-up, and slowing down abdominal and intestinal spasms.

 

• Many colics benefit from a nasogastric tube (NG tube) to relieve pressure from gas build-up, hydrate your horse, and appropriate medications. Often, mineral oil is given, but this may not be appropriate for some gas colics.

 

• Gas colics MAY benefit from light handwalking to encourage passing gas. Walking can worsen other colic situations. An appropriate plan of action from your vet is the best place to start. The goal for gas colics is to free the gas into the world without making your horse tired from walking, in addition to the energy needed to combat pain. It’s exhausting not feeling well, and walking can compound this problem.

 

Although you can see ribs on this horse, they may still have a metabolic disorder, or be pregnant! 

 

Preventative Strategies for Spring Colic

 

• Horse care would be much easier if we could tell them to take it easy on the sweets! But, like kiddos, sweets can be so tempting.

 

• When designing an anti-gas colic plan, remember these two essential things: Spring grass is a diet change, and you must know your horse’s metabolic status.

 

Know your horse’s metabolic status

 

• Any horse with a metabolic disorder already has a higher risk of colic and laminitis. The green spring grass will raise this risk, as it will with a young horse without metabolic challenges. Think of a metabolic disorder as a head-start to hindgut problems that create laminitis and gas.

 

• Both pituitary pars intermedia disorder (PPID, formerly known as Cushing’s disease in horses) and equine metabolic syndrome (EMS) change insulin and sugar regulation in the body, which raises the risks.

 

• Simple blood tests can tell you the metabolic status, and sometimes, medications can help regulate them. Ensuring your horse’s diet is low-sugar and low-starch is the best management change. This includes hay, grains, commercial feeds, supplements, and pasture.