10 Things You Might Not Know About The Horses Respiratory System
1. The horse only breathes through its nostrils. They do not breathe through their mouths unless they have an injury or abnormality to the soft palate.
2. At canter and gallop normal horses take one breath perfectly in time with one stride.
3. The amount of air moved in and out of the lungs increases in direct proportion to how fast the horse is running.
4. When horses inhale during exercise, around 90% of the resistance (obstruction) to air movement is in the airways that are in the head, namely, the nostrils, the nasal passages, and the larynx. But when horses are exhaling the majority of resistance to air movement (55%) is in the airways within the lung.
5. If you tighten a horse’s girth too much, it will affect the horse’s performance–not because of constricting the chest and preventing the lungs from expanding, but because it decreases the effectiveness of the muscles around the front of the chest and shoulder that move the forelegs.
6. Horses do not breathe by expanding and contracting their chests during the canter and gallop. They expand and contract the chest when breathing at rest, when breathing at walk and trot, and perhaps most noticeably when blowing hard after exercise. But during canter and gallop all air movement comes from movement of the diaphragm.
7. Horses hold their breath over jumps and do not breathe again until they land, starting with breathing out.
8. You cannot train the respiratory system of the horse. The amount of air moved in and out by an unfit horse at a fixed speed will be the same six months later when that horse is fully fit.
9. The pressure in the blood vessels within the horse’s lungs during galloping is four to five times higher than resting pressure.
10. If all the airways in the lung were opened out and laid flat on the ground, they would occupy a total area equivalent to 10 tennis courts.
Reference: Marlin, D. (2007). The Airways and Lungs.