Meeting Abstract
Hemoglobin (Hb) and hematocrit (Hct), two major predictors of oxygen carrying capacity, are thought to contribute to variation in individual aerobic performance. Indeed, these blood parameters seem to vary adaptively in response to important life-history events in birds, such as breeding, migration, and winter acclimatization. Most of the current studies investigating individual variation in hematology, aerobic capacity, and life-history are correlational. Thus, there would be considerable value in developing methods for experimental manipulation of Hb and Hct, but existing methods are either expensive or use pharmacological agents with potentially harmful side effects. Recently it was reported that nitrate administration can effectively lower Hb and Hct in mammals (rats). Dietary nitrate is endogenously reduced to nitric oxide (NO) via the nitrate-nitrite-nitric oxide pathway. NO is, in turn, hypothesized to increase mitochondrial efficiency, lowering the oxygen cost of exercise and thus allowing for the down-regulation of blood parameters such as Hb and Hct. We attempted to confirm and validate this finding in birds by conducting three dose-response studies in captive zebra finches (Taeniopygia guttata). Preliminary analysis suggests that there is no consistent effect of nitrate on blood parameters in this species (cf. mammal studies). We will report results of further experimental trials and measurements of plasma nitrate concentration in our experimental subjects. Specifically, we will test the prediction that birds dosed with higher concentrations of nitrate will have higher plasma nitrate levels and will show a dose-dependent modulation of Hct and Hb.
