Part 2: The information that a blood count and blood analysis can give on a horse’s health before a race or performance.
What are the main reasons for routine blood analysis?
Pre-racing or pre-performance, to make sure that the horse is healthy and the bloods within the horse’s normal range.Post-racing or after a poor performance where no other obvious reason is apparent.Horse not thriving.Horse lethargic or as a term often used by owners /trainers/riders, “horse dead in himself”Horse sick – a blood analysis will most likely give the cause.Response to treatment - if a blood test is taken at the early stages of the disease or condition and again after a specific period of treatment on the prescribed medication course, the blood analysis can give an indication whether or not that drug is working effectively.What are the important parts of blood that the veterinary surgeon has to interpret and analyse?
Blood is made up of cells and plasma and has a variety of functions. Blood is approximately 60% water, approx 39% blood cells and the remainder (approx 1%) is comprised of hundreds of elements, electrolytes, enzymes and proteins. The WBCs are far less numerous than the red blood cells.To understand how it works, the major components of the horse’s blood must be considered separately. The three main types of cells in blood are: Red blood cells (RBCs or erythrocytes) White blood cells (WBCs or leucocytes)Platelets (karyocytes) What are the functions of these different cells in the blood?
All of the various components in the horse’s blood have important functions:Red blood cells (the commonest cells), contain haemoglobin and its main function is to carry oxygen throughout the body, from the lungs to the tissues and to take carbon dioxide or waste products from the tissues to the lungs where it is exhaled from the horse’s body. It is the haemoglobin that gives blood its red colour.White blood cells carry out immune system functions mainly. WBCs are sometimes described as the ‘policemen’ of the horse’s body. They respond to injury, infection, allergies, stress, immune reaction etc. There are five major types of WBCs each performing a different function: (1) neutrophils, (2) lymphocytes, (3) eosinophils, (4) monocytes and (5) basophils. Details of each of their status is recorded routinely on the blood test report.Platelets are a smaller type of cell which are involved in the clotting mechanism in the horse’s body.Plasma is the fluid part of blood. It is a complex solution of electrolytes (salts), mainly sodium and chloride. Plasma also contains proteins, which have a range of functions. What can a blood sample tell us about a horse?
As the horse is an athletic animal and requires peak fitness performance to achieve success, very slight variations in blood counts can affect his performance.Blood tests can pick up signs of infection, blood disorders, hormonal, liver, kidney, bowel, as well as conditions such as Azoturia or “Tying Up”. They also aid assessment of severity and prognosis of a condition or disease and can be used to monitor long-term conditions or to check response to treatment. As blood has a major role in the metabolism of most of the horse’s body tissues, changes in its composition can be an effective aid to diagnose disease.Variations in the number of white blood cells can give important clues, among other things, as to the presence of an inflammation in the horse. Both the WBC count and the proportion of the different types of WBCs varies according to the nature and duration of the horse’s disorder. So while one might expect the response to infection and other forms of inflammation to be an increase in the WBC count, this is not always the case.A common misconception is that it is possible to definitively distinguish between viral and bacterial infections on the basis of the proportion of white blood cells present in a sample. When all is normal, most of the blood components are regulated to a very narrow concentration that varies only slightly from horse to horse. Because of this, a reference range for what is normal is available for comparison. This is indicated on the blood report sheet in order to compare it with the individual horse’s result.Many blood components change in a very predictable way relative to a disease process so blood tests can be extremely valuable aids in disease diagnosis and determining health status.Do all horses have the same normal readings?
Horses show slight variations in the normal levels in most cases. For this reason it is important to have a baseline on blood readings of each horse when it is performing at its best. If at any stage subsequently, its blood readings are showing significant deviations from the usual normal readings of this horse, then it may very often be advisable not to race or perform until the bloods have been corrected and normal levels have been re-established. Likewise if a horse has performed poorly, a blood test can be taken the following day and compared with the baseline readings. This will often give a good reason for its drop in performance standards.