How the Respiratory System Works and Why It Is Important | Equine Science Matters™

A horse’s respiratory system is responsible for bringing oxygen into the body and removing carbon dioxide. Oxygen is essential because it allows the muscles, organs, and tissues to work properly, especially during exercise. 

Air enters through the nostrils and travels through the nasal passages at the back of the nose and throat. Horses are known as “obligate nasal breathers,” which means they can only breathe through their noses, not their mouths. This is because a structure called the soft palate blocks airflow through the mouth to the windpipe. 

From the throat, air passes through the larynx (voice box) and down the trachea, also known as the windpipe. The trachea then splits into two large airways called bronchi, one leading to each lung. These continue to branch into smaller tubes called bronchioles, which end in tiny air sacs called alveoli. 

The alveoli are where gas exchange takes place. Oxygen moves from the lungs into the bloodstream, while carbon dioxide moves from the blood into the lungs to be breathed out. The oxygen-rich blood is then pumped around the body to supply the muscles and organs with the oxygen they need. 

A healthy horse at rest usually takes around 8–16 breaths per minute. During light to moderate exercise, this can increase to around 50–80 breaths per minute to meet the body’s increased oxygen demands. 

Almost every single cell in the body, no matter its function, requires an adequate supply of oxygen to function correctly. A healthy respiratory system is essential for everything from nerves, muscles, cartilage, and other anatomical structures, both during exercise and everyday activity.

Common signs of respiratory problems in may horses include: 

• Coughing  

• Nasal discharge  

• Fast or difficult breathing  

• Wheezing  

• Reduced performance during exercise and exercise recovery 

• Poor appetite or weight loss 

It is worth noting that horses have a very low cough reflex, meaning that a cough often doesn’t appear until there is already an established issue. 

Common reasons for poor respiratory health and reduced performance  

Asthma, viral and bacterial infections are common causes of poor respiratory health. Alongside this, environmental and management factors like dust, spores, ammonia build-up and seasonal allergens can be a factor.   

Tack can affect a horse’s breathing and movement if it is too tight or restrictive. Tight nosebands and harsh bits may limit airflow by changing the position of the head, neck, and soft tissues in the throat, making it harder for the horse to breathe properly and reducing performance (Mellor and Beausoleil, 2017).  

Consequences of poor respiratory health 

Poor respiratory health can reduce a horse’s stamina and cause fatigue. When a horse cannot get enough oxygen, it relies more on anaerobic exercise, which leads to a build-up of lactic acid in the muscles. This can result in muscle tiredness, slower recovery, reduced endurance, and lower performance. 

Ways to help prevent and manage respiratory problems include: 

• Providing dust-free forage and good stable ventilation  

• Soaking or steaming hay to reduce dust, spores, and bacteria  

• Using low-dust bedding  

• Keeping the horse well hydrated, as dehydration can thicken mucus and worsen breathing problems  

• Improving airflow by keeping stable windows and doors open where possible  

• Ensuring tack fits correctly and avoiding overly tight nosebands, which can restrict the airway during exercise 

In conclusion, the respiratory system plays a vital role in a horse’s overall health, well-being, and athletic performance. Efficient breathing allows oxygen to be delivered to the muscles and organs, supporting movement, stamina, and recovery after exercise. When respiratory function is compromised by illness, stable management issues, environmental irritants, or restrictive tack, performance, recovery and comfort can quickly decline. Recognising early signs of respiratory problems and maintaining good management practices are essential steps in supporting long-term respiratory health and helping horses perform comfortably and reach their potential. 

Mellor, D. and Beausoleil, N. (2017). Equine Welfare during Exercise: An Evaluation of Breathing, Breathlessness and Bridles. Animals, 7(12), p.41. Available at:https://doi.org/10.3390/ani7060041.