SUMMARYA water deprivation test was developed for the differentiation of polyuric disorders in birds using the racing pigeon as a model. For a period of 3 days of food and water deprivation, urine and plasma osmolalities and body weight of 40 clinically healthy racing pigeons were monitored. Reference values for urine osmolality after 40 hours of food deprivation were 79 to 480 mOsmol/kg. After 64 hours of food deprivation and 24 hours of water deprivation these values were 450 to 875 mOsmol/kg. No significant rise in urine osmolality was seen after the first 24 hours of water deprivation. It is concluded that an urine osmolality greater than 450 mOsmol/kg is indicative of a normal concentrating capacity of the kidney in the pigeon. Data from the literature suggest that these values can be applied to other avian species.
INTRODUCTIONThe water deprivation test has proved useful in differentiating between the causes of polyuria and polydipsia (PUPD) in dogs (Joles and Mulnix, 1977). The principle of this test is to determine whether the neurohypophyseal antidiuretic hormone arginine vasopressin (AVP) is released in response to dehydration and whether the kidneys can respond to this stimulus. With this test differentiation between central diabetes insipidus, nephrogenic diabetes insipidus, primary (psychogenic) polydipsia and hyperadrenocorticism is facilitated (Joles and Mulnix, 1977). In birds arginine vasotocin (AVT) replaces AVP as the main physiological regulator of body water balance. Neurohypophysectomy in the domestic fowl results in polyuria while administration of AVT restores urine flow to normal levels (Shirley and Nalbandov, 1956).
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