CERASALE, D.J.; GUGLIELMO, C.G.; University of Montana; University of Montana: Plasma phospholipid levels and triglyceride:phospholipid ratio as indicators of mass change and diet lipid quality in wild birds

Plasma metabolite profiling has received recent attention as a means to assess body mass changes in migratory birds. Prior studies have focused on triglycerides as the main transport form of dietary fatty acids to fat stores. Ingested lipids used for mass gain, however, can also be absorbed as phospholipids. Plasma phospholipids thus may represent a significant pathway for absorbed lipids during refueling, and when measured may improve analyses predicting body mass changes in wild birds. In invertebrates, the ratio of triglyceride to phospholipid content is a measure of relative fat storage because triglycerides are used for energy storage while phospholipid content is a function of absolute body size. Thus, triglyceride:phospholipid ratio in avian plasma may reflect the nutritional quality of consumed prey. We studied a captive passerine fed diets differing in phospholipid content and triglyceride:phospholipid ratio. Plasma phospholipid levels were higher in birds fed a diet high in phospholipid content. Contrary to our expectations, plasma phospholipid levels related negatively to body mass changes and did not improve plasma metabolite profiling techniques. Plasma triglyceride:phospholipid ratio was lower in birds fed a diet with high phospholipid content and low triglyceride:phospholipid ratio. We conclude that plasma triglyceride:phospholipid can provide valuable information regarding diet lipid quality, but more research is needed to elucidate the role of phospholipids in avian lipid metabolism and fat deposition.