By the time a horse crosses the finish line in a 5 furlong race, has completed a Grand Prix showjumping round or gone 1/6th of the way round a 3-star cross-country course it will have moved somewhere around 1800 litres of air in and out of the lungs. If you find 1800 litres hard to visualise, then think of 6 baths of air. This equates to moving two buckets of air into and out of the lung every second. The air breathed in (inhaled) during a race will consist of around 380 litres of oxygen (the rest being made up of the gas nitrogen), and the horse will take up into the blood and use around a quarter of this oxygen i.e. 95 litres.
Of the total amount of energy the racehorse needs to get from the starting gate to the finish in the 5 furlong race, around 70% of this will come from aerobic metabolism (also around 70% for showjumping and 90% for cross-country). Aerobic metabolism is essentially the process of getting energy from glucose [carbohydrate] in structures inside the muscle cells known as mitochondria using oxygen. The remainder comes from anaerobic metabolism – this also breaks down glucose to generate energy but this process can work whether oxygen is present or not. The main difference here is that anaerobic is very fast but inefficient, and can be used for only a short period of time due to build up of lactic acid, whilst aerobic is not so fast but very efficient at generating the energy to run.
So, even in a race or jumping round lasting less than a minute, the majority of the energy generated by the muscles must come from using oxygen to “burn” carbohydrates. Even in a barrel race, around 40% of the energy to run still comes from aerobic metabolism. These examples underline the importance of a respiratory system. The harder a horse works, the more oxygen it needs and the more air it must move into and out of the lungs. In fact, these are so tightly coupled that if a horse doubles its speed, it will need to double the amount of air moved into and out of the lungs.
The respiratory system moves air containing oxygen from outside the body to inside the lungs bringing the oxygen as close as possible to the blood in the circulation.
Air moving outside the body passes first through the upper respiratory system including the nostrils, the nasal passages and larynx and then into the trachea (or windpipe).
The horse’s windpipe is around 5-8cm in diameter nearest the larynx, but as it passes deeper in the lung it begins to divide to produce smaller and smaller airways, much like a tree on its side. Each time an airway divides in two, the “daughter” airways are smaller than the “parent” from which they arose. When we get down to the level of the smallest airways, after perhaps 25 divisions, the airways are fractions of a millimetre in size. When the air gets to this point in the chain from nostril to muscle cell, it has to cross from the air space (“alveoli”) into the blood vessel At this stage, the membranes separating the oxygen containing air in the alveoli from the red blood cells in the blood vessel are only the thickness of 1/100th the width of a human hair. The transfer of oxygen from the alveoli across this thin membrane and into the blood does take place by the process of diffusion i.e. the oxygen moves from high (in the air) to lower (in the blood). Incidentally, the total area for oxygen to diffuse across in the horse is equivalent to the area of 10 tennis courts!
By the time a horse crosses the finish line in a 5 furlong race, has completed a Grand Prix showjumping round or gone 1/6th of the way round a 3-star cross-country course it will have moved somewhere around 1800 litres of air in and out of the lungs. If you find 1800 litres hard to visualise, then think of 6 baths of air. This equates to moving two buckets of air into and out of the lung every second. The air breathed in (inhaled) during a race will consist of around 380 litres of oxygen (the rest being made up of the gas nitrogen), and the horse will take up into the blood and use around a quarter of this oxygen i.e. 95 litres.Of the total amount of energy the racehorse needs to get from the starting gate to the finish in the 5 furlong race, around 70% of this will come from aerobic metabolism (also around 70% for showjumping and 90% for cross-country). Aerobic metabolism is essentially the process of getting energy from glucose [carbohydrate] in structures inside the muscle cells known as mitochondria using oxygen. The remainder comes from anaerobic metabolism – this also breaks down glucose to generate energy but this process can work whether oxygen is present or not. The main difference here is that anaerobic is very fast but inefficient, and can be used for only a short period of time due to build up of lactic acid, whilst aerobic is not so fast but very efficient at generating the energy to run.So, even in a race or jumping round lasting less than a minute, the majority of the energy generated by the muscles must come from using oxygen to “burn” carbohydrates. Even in a barrel race, around 40% of the energy to run still comes from aerobic metabolism. These examples underline the importance of a respiratory system. The harder a horse works, the more oxygen it needs and the more air it must move into and out of the lungs. In fact, these are so tightly coupled that if a horse doubles its speed, it will need to double the amount of air moved into and out of the lungs.The respiratory system moves air containing oxygen from outside the body to inside the lungs bringing the oxygen as close as possible to the blood in the circulation.Air moving outside the body passes first through the upper respiratory system including the nostrils, the nasal passages and larynx and then into the trachea (or windpipe).The horse’s windpipe is around 5-8cm in diameter nearest the larynx, but as it passes deeper in the lung it begins to divide to produce smaller and smaller airways, much like a tree on its side. Each time an airway divides in two, the “daughter” airways are smaller than the “parent” from which they arose. When we get down to the level of the smallest airways, after perhaps 25 divisions, the airways are fractions of a millimetre in size. When the air gets to this point in the chain from nostril to muscle cell, it has to cross from the air space (“alveoli”) into the blood vessel At this stage, the membranes separating the oxygen containing air in the alveoli from the red blood cells in the blood vessel are only the thickness of 1/100th the width of a human hair. The transfer of oxygen from the alveoli across this thin membrane and into the blood does take place by the process of diffusion i.e. the oxygen moves from high (in the air) to lower (in the blood). Incidentally, the total area for oxygen to diffuse across in the horse is equivalent to the area of 10 tennis courts!
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By the time a horse crosses the finish line in a 5 furlong race, has completed a Grand Prix showjumping round or gone 1/6th of the way round a 3-star cross-country course it will have moved somewhere around 1800 litres of air in and out of the lungs. If you find 1800 litres hard to visualise, then think of 6 baths of air. This equates to moving two buckets of air into and out of the lung every second. The air breathed in (inhaled) during a race will consist of around 380 litres of oxygen (the rest being made up of the gas nitrogen), and the horse will take up into the blood and use around a quarter of this oxygen i.e. 95 litres.
Of the total amount of energy the racehorse needs to get from the starting gate to the finish in the 5 furlong race, around 70% of this will come from aerobic metabolism (also around 70% for showjumping and 90% for cross-country). Aerobic metabolism is essentially the process of getting energy from glucose [carbohydrate] in structures inside the muscle cells known as mitochondria using oxygen. The remainder comes from anaerobic metabolism – this also breaks down glucose to generate energy but this process can work whether oxygen is present or not. The main difference here is that anaerobic is very fast but inefficient, and can be used for only a short period of time due to build up of lactic acid, whilst aerobic is not so fast but very efficient at generating the energy to run.
So, even in a race or jumping round lasting less than a minute, the majority of the energy generated by the muscles must come from using oxygen to “burn” carbohydrates. Even in a barrel race, around 40% of the energy to run still comes from aerobic metabolism. These examples underline the importance of a respiratory system. The harder a horse works, the more oxygen it needs and the more air it must move into and out of the lungs. In fact, these are so tightly coupled that if a horse doubles its speed, it will need to double the amount of air moved into and out of the lungs.
The respiratory system moves air containing oxygen from outside the body to inside the lungs bringing the oxygen as close as possible to the blood in the circulation.
Air moving outside the body passes first through the upper respiratory system including the nostrils, the nasal passages and larynx and then into the trachea (or windpipe).
The horse’s windpipe is around 5-8cm in diameter nearest the larynx, but as it passes deeper in the lung it begins to divide to produce smaller and smaller airways, much like a tree on its side. Each time an airway divides in two, the “daughter” airways are smaller than the “parent” from which they arose. When we get down to the level of the smallest airways, after perhaps 25 divisions, the airways are fractions of a millimetre in size. When the air gets to this point in the chain from nostril to muscle cell, it has to cross from the air space (“alveoli”) into the blood vessel At this stage, the membranes separating the oxygen containing air in the alveoli from the red blood cells in the blood vessel are only the thickness of 1/100th the width of a human hair. The transfer of oxygen from the alveoli across this thin membrane and into the blood does take place by the process of diffusion i.e. the oxygen moves from high (in the air) to lower (in the blood). Incidentally, the total area for oxygen to diffuse across in the horse is equivalent to the area of 10 tennis courts!
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