PIERCE, B.J.*; MCWILLIAMS, S.R.; O’CONNOR, T.P.; GUGLIELMO, C.G.; Univ. Rhode Island; Univ. Rhode Island; City Univ. New York; Univ. Montana: Fatty acid composition of body fat and its affect on aerobic performance in Red-eyed Vireos
Most migrating birds accumulate large lipid stores as their primary source of energy for fueling long distance flights. The depot fat of birds is usually composed of mostly unsaturated fatty acids when the birds are migrating, suggesting a possible functional advantage to having a specific fatty acid profile. Whether birds preferentially store and utilize unsaturated fatty acids in order to maximize their performance during migration is unknown. We fed 10 red-eyed vireos either a diet containing cottonseed oil and palm oil (CP) (62% UFA and 38% SFA), or olive oil (OL)(82 % UFA and 18% SFA) for four months. We then measured oxygen consumption rates of birds at rest and during intense exercise (using a “hover-flight” wheel). We also measured blood metabolites prior to and immediately following exercise to determine use of endogenous fat reserves and if utilization of triglycerides differed between vireos fed each diet. Fatty acid composition of body fat in red-eyed vireos was similar to the fatty acid composition of their respective diets. Mass-specific resting metabolic rates (RMR) (mlO2g Mb/hr) were similar between vireos fed the CP diet (2.75 ±0.32) and the OL diet (2.30 ±0.30). However, mass-specific active metabolic rates (AMR) of vireos fed the CP diet (27.38 ±1.36) were on average higher than those of vireos fed the OL diet (21.31 ±1.79). The average ratio of unsaturated to saturated fatty acids in the depot fat of songbirds during migration is 67% and 33%, respectively. Our results show that a similar ratio produced the higher mass-specific active metabolic rates in exercising vireos suggesting that this ratio of fatty acids may be an optimal composition for migrating songbirds.
