Horse’s Vital Signs
A sound understanding of your horse’s vital signs can be used to determine the state of your horse’s health and current fitness levels. Awareness of your horse’s vital signs will enable you to differentiate between what is considered ‘normal’ and ‘abnormal’ for your horse. This basic understanding will also provide you with the knowledge required to quickly and easily detect signs of injury, illness or metabolic distress in addition to being able to effectively monitor your horse’s training regimen and rates of return following exercise.
The horse’s vital signs outlined in this article will enable you to perform a physical examination that can be used to assess any changes in your horse’s demeanour, respiratory and cardiovascular health, body temperature and identify evidence of metabolic stress such as dehydration.
Horse’s Vital Signs and common measures of equine health include:
- Resting heart rate (RHR) 36-42 beats per minute (BPM).
- Respiration rate (RR) 8-14 breaths per minute.
- Body temperature: 37.4-38.4ºC.
- Gut sounds.
- Hydration level: skin turgor test should retract in 1 second.
- Capillary Refill Time (CRT) should be 1-2 seconds.
- Mucous membranes should be a healthy pink colour.
How to measure a Horse’s Vital Signs:
- Heart rate (HR): A horses pulse is indicative of blood being pushed through the arteries. The pulse is able to be felt in various blood vessels located close to the skin’s surface which include the inside edge of the lower jaw, beneath the chestnut in the front legs, the inside surface of the cannon bone below the knee and beneath the dock. The pulse rate is affected by the level of exercise, ambient temperature, fitness level, excitement, age (younger animals tend to have a higher pulse rate) and presence of disease or gastrointestinal disturbances. When feeling for a pulse, ensure that three fingers are used (and not the thumb as it contains a pulse). The pulse rate of a fit horse should return to normal 30 minutes after aerobic exercise.
- Respiration rate (RR): Is the sequential movement of air into and out of the lungs, commonly known as inhalation and exhalation. The respiration rate is affected by fitness level, ambient temperature, high humidity, excitement, illness and pain. A horse’s respiration rate can be monitored by observing the ribcage for the sequential inhalation and exhalation movements at the curve of the flank or nostrils.
- Temperature: May be mildly affected by environmental temperature extremes, exercise and excitement, however, usually remains within the critical range. Elevated core temperatures may be indicative of disease, overheating or colic and result in an impaired contractile function of the muscle fibres, contributing to fatigue and exhaustion. Conversely, temperatures below the normal range can be a result of shock, chilling or a horse that is critically ill. Certainly, foals are more susceptible to temperature fluctuations as a result of changes in the ambient temperature.
- Gut sounds: The noises which resound from the gut are a result of digestion taking place within the gastrointestinal tract (GIT). Depending on the location of the sound, the location within the GIT is able to be identified. Gut stasis (a lack of gut noise) is indicative of digestive disturbances such as colic and conversely, a hyper-motile (abundance of gut noise) gut is an indication of a digestive irritation which may be associated with diarrhoea.
- Hydration: The degree of hydration is a measure of the level of fluids in the body which can be gained through drinking, drenching or intravenously. Dehydration occurs when the body fluid loss exceeds the level of intake and may be predisposed by a lack of fluid intake, diarrhoea, excessive sweating and fevers, blood loss and urination. The extent of water loss during exercise depends on the level of fitness, in addition to the availability of water and electrolytes before, during and immediately after exercise. The skin turgor test is the most common method for the detection of dehydration whereby skin which remains elevated following this test is indicative of serious dehydration of approximately 7-10% of body fluid loss. It should be considered that a 500kg horse can lose as much as 40L of water through sweat during extended periods of exercise and important symptoms for identifying dehydration include coldness and fatigue, muscular tremors, colic, thumps, unresponsiveness, lack of appetite and a low pulse: respiration ratio.
- Capillary Refill Time (CRT): Provides an indication of the time taken for blood to return to the surface of the mucous membranes following the application of pressure. A reduced CRT is an indication of a reduced blood volume and pressure caused by dehydration, blood loss or shock. The CRT is able to be assessed by raising the horse’s upper lip and applying a finger on the gums for 3-4 seconds with sufficient force to leave a white mark. If the horse is healthy, hydrated and has good circulation the pink colouration will return within 1-2 seconds.
- Mucous membranes: The major mucous membranes are found on the inside of the mouth, eyelids and nostrils. These membranes are highly vascularized and the colour of the membrane may be used to provide information indicating the level of circulation, anaemia, colic, illness, shock or a fever. A horse with healthy circulation should display a rich, pink colour while a pale pink colour occurs when the capillaries are contracted and may be indicative of a fever, blood loss or anaemia while a bright red colouration occurs when the capillaries become enlarged in times of toxicity or mild shock. In the case of membranes appearing grey or blue, the horse is most likely suffering from severe shock and/or illness.