BLOOD-VISCOSITY IN BROILERS - INFLUENCE ON PULMONARY-HYPERTENSION SYNDROME

Elevation in apparent blood viscosity may enhance the pulmonary hypert ension that leads to pulmonary hypertension syndrome (PHS) and ascites in fast-growing broilers. We investigated the importance of packed ce ll volume (PCV) and shear rate in modifying apparent viscosity of the blood from broilers assigned to normal, preascites, and ascites groups . Apparent viscosity of broiler blood increased at all shear rates as PCV increased; the increase in apparent viscosity became greater as th e shear rate decreased at PCV above 0.30. At the PCV of normal broiler s (0.30 or below), apparent viscosity was nearly shear rate independen t, at least down to 11.25 per second, the lowest shear rate studied. A pparent viscosity, at any given PCV and shear rate, was significantly lower in the blood of birds with ascites than in normal birds; however , the relative viscosity was not different between those groups, indic ating that lower plasma viscosity in the birds with PHS was responsibl e for the finding. The results show that the principal factor responsi ble for increased apparent viscosity of blood in birds with PHS is the increase in PCV. The increased resistance to flow of blood as the res ult of higher blood viscosity may contribute to the pulmonary hyperten sion.