Blood Chemistry and Hematocrit of Captive and Wild Canvasbacks

Abstract

Blood chemistry and packed cell volume (PCV) did not vary among groups of captive canvasbacks (Aythya valisineria) maintained ad libitum on 5 diets varying in metabolizable energy (ME) and protein. Ducks fed low quality diets increased their consumption so that all ducks were obtaining similar amounts of energy and protein. Some variables, including cholesterol, were found to differ between the sexes and ages of captive ducks. Seasonal differences were detected in the blood chemistry of captive canvasbacks. Four of the 5 enzyme values increased from October to January and then declined to April. PCV increased from 45 in October to 51 in April. Overall, blood chemistry values and PCV's were highly variable and did not appear to be good discriminators for age, sex, and diet of captive canvasbacks. Differences detected between captive and wild canvasbacks were attributed to increased stress of wild ducks during handling. J. WILDL. MANAGE. 50(3):435-441 Most studies dealing with avian blood have been conducted with chickens and other domestic birds (Lucas and Jamroz 1961, Sturkie 1976), and their emphasis has been on hematology rather than blood chemistry. Other studies have been conducted on the blood of birds other than Anseriformes (Ronald et al. 1968, Carey and Morton 1976, Rehder et al. 1982, Parrish and Mote 1984). Gee et al. (1981) compared differences in 25 blood chemistry values among 12 captive avian species; 7 of these were endangered species and included quail (Odontophorinae), raptors (Falconiformes), cranes (Gruidae), and geese (Anserini). Several researchers have demonstrated that the physiological condition of birds can influence blood values (Altman and Dittmer 1964, Dolnik 1973, Driver 1981). Gee et al. (1981) showed differences in blood values due to sex; however, Mulley (1979, 1980) was unable to demonstrate differences in blood chemistry and hematology due to sex with 2 duck species in Australia. Other researchers have shown the effect of age (Leonard 1969, Sturkie 1976). Woerpel and Rosskopf (1984) reviewed the use of blood chemistry as an aid in the diagnosis of disease and illness in caged birds. Several research studies have been conducted concerning factors affecting certain blood values of waterfowl. Wood and Hofman (1967) found that blood values of mallards (Anas platyrhynchos) could be influenced by artificial stimulation of reproduction, and Wood and Smoes (1968) reported the effects of reproducti e suppression on the blood of mallards. Mori and George (1978) studied seasonal effects on certain blood serum variables of Canada geese (Branta canadensis). Kocan (1972) conducted hematological analyses on 54 canvasbacks from Chesapeake Bay. Although PCV for male and female canvasbacks overlapped, there was a tendency for higher values in females (. = 53) than in males (9 = 51). In another sample of canvasbacks Kocan and Pitts (1976) reported higher PCV values in females than males although ages were not determined. They stated that differences observed among adult ducks probably reflected hormonal and nutritional differences brought about by changing photoperiod and migration. Hemm and Carlton (1967) reported conflicting PCV data in ducks due to age and sampling variability. More recent reports on waterfowl PCV values show little differences between sexes (Williams and Trainer 1971, Shave and Howard 1976, Mulley 1979). There are indications that differences in PCV exist between dabbling and diving ducks (Bond and Gilbert 1958, Shave and Howard 1976). The influence of nutrients on the blood chemistry of waterfowl has not been determined adequately. Newberne (1975) discussed the importance of diet in research experiments with regard to changing physiological processes, but he did not give specific examples of changes that occurred in blood due to diet. Most blood analyses conducted with waterfowl have been done with breeding ducks with emphasis