Meeting Abstract
Blood carries the oxygen supply for aerobic metabolism. Hematological variables (HV), specifically hemoglobin concentration (Hb), hematocrit (Hct), erythrocyte count (RBCc) and area (RBCarea) may affect metabolic performance. However, the relationships between these four HVs and metabolic rate have not been explored in adult birds. We manipulated the energy requirements of female zebra finches (Taeniopygia guttata) by exercising them and investigated if specific HVs are related to energy expenditure and set limits to metabolic performance. In outside aviaries 56 birds were flight exercised twice a day for 90 min, while 46 birds remained as non-exercised controls. After 6 weeks the HVs, rho-phase basal metabolic rate (BMRρ) and maximum metabolic rate (MMR) were determined, and in a subset of 17 birds along with daily energy expenditure (DEE). Exercised birds had lower MMR than controls, but BMRρ, and DEE did not differ between groups. We attribute this to distinct thermoregulatory responses in treatment groups that masked exercise effects. Principal components (PC) were derived from HVs, and tested for their relationship to BMRρ, MMR and DEE. Hb, Hct and RBCc were positively associated with PC1, and explained 60% of variation, while RBCarea had the highest positive input in PC2. MMR was not related to PC1 and PC2. BMRρ and DEE were significantly affected by interaction between PC1 and treatment. Interestingly, PC1 was positively related to BMRρ, but negatively to DEE, which was only significant in the exercised group. To conclude, MMR appears not to be driven by HVs, while BMRρ and DEE seem to be related to the combined levels of Hb, Hct and RBCc, however in the opposite direction and only under exercise conditions.
