2 Simple Diagnostic Tests This is a useful test when trying to clarify a diagnosis with the thin horse or the animal with chronic diarrhoea. It is equally as useful in mules and donkeys. It is easy to perform in the field and is not expensive, but is rather time consuming. The horse is starved for 12 h, usually overnight. A blood sample is then taken for immediate glucose estimation. A human glucometer, as used for diabetic patients, is ideal. The horse is then stomach-tubed with glucose dissolved in water (1 g/kg body weight). The volume should be 1 ml/kg. Thus a 500 kg horse should receive 0.5 kg of glucose dissolved in 0.5 l. The horse should be starved throughout the test. A second sample should be taken after 2 h and then at hourly intervals for a further 2 h. The blood glucose level in a normal horse will be ~8 mmol/l at the start, which should rise to >12 mmol/l within 2 h. This level will slowly decline, but will still be >10 mmol/l after 4 h. On the other hand in a horse with a malabsorption problem, e.g. a generalized intestinal lymphosarcoma, the level will never reach 10 mmol/l and will return to pre-glucose levels within 4 h. Sadly, the outcome for a horse with low glucose absorption is bad. However, it does mean that the clinician can advise euthanasia earlier in the course of a disease and thus prevent further suffering. Foals are born with no effective immunity. Their survival depends on obtaining the effective passive transfer of immunoglobulins via the colostrum of the mare, as soon after birth as possible. This has to be ingested quickly as the tiny portals of entry, in the foal’s intestine, for such large protein particles close within 24 h. The ideal scenario is for adequate colostrum to be ingested within 3 h; however, 6 h is the accepted cut-off point. Obviously, colostrum obtained after this time is still beneficial but it may not be life-saving. The quality of the colostrum is important: sick or debilitated mares will have poor-quality colostrum. A test for colostrum quality is described later. Also some mares, particularly multiparous mares, will produce milk several days before birth; ideally, this should be stored in a refrigerator pending the birth of the foal. There is a fine balance with heavily pregnant mares; the udder should be left completely alone to avoid this milk flow. An occasional small degree of milk flow should be ignored. Trying to catch this small, worthless sample will only stimulate the mare to produce more and therefore defeat the whole exercise. If mares are foaling in groups it is very sensible to collect some colostrum from an older mare with plenty of colostrum. Obviously the older mare must be allowed to give her own foal sufficient colostrum, but after 6 h some 250 ml can be collected and then stored in a deep-freeze unit. Should this colostrum be required it should be defrosted, either at ambient temperature in hot countries or in a bowl of hot water in colder climates. Colostrum may be defrosted in a microwave, but only at the defrosting setting. If it is defrosted at a higher cooking setting, vital proteins will be denatured. Ideally, therefore, we need an estimation of the foal’s immunological status as early as possible. The zinc sulfate turbity test can be performed at 12 h. The value of performing the test at this stage is great. Most foals will not develop septicaemia and show signs of illness until 24–48 h. Antibiotics given early systemically are beneficial, but not nearly as beneficial as good-quality colostrum or serum from an immune donor. There are other tests available, but these are expensive and difficult to perform. If the serum is sent away to a laboratory the result will be received too late. Obviously, if it is known that the foal has not received colostrum in the first 6 h because the mare has died, the foal has not become ambulatory or the mare has totally rejected the foal, there is no need to perform the test as the immune status of the foal is known, i.e. it is naive. Alternative measures have then to be implemented. It is only when the immune status is unknown that there is a need to perform the zinc sulfate turbity test. Dissolve 250 ml zinc sulfate in 1 l of freshly boiled water. Place 6 ml of the solution into several plain vacuum tubes (usually these have a red stopper). These tubes will last for months, so may easily be prepared and stored at room temperature. Carbon dioxide, which causes cloudiness, is the main problem. However, this will have been removed by boiling, and the vacuum in the tubes will prevent any contamination.
2.1 Glucose Absorption Test
2.2 Zinc Sulfate Turbity Test
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