Dietary polyunsaturated fatty acids influence flight muscle oxidative capacity but not endurance flight performance in a migratory songbird
Bibliographic record
Abstract
The migratory flights of birds are primarily fueled by fat; however, certain fatty acids may also enhance flight performance and the capacity to oxidize fat. The natural doping hypothesis posits that n-3 long-chain polyunsaturated fatty acids (PUFA) increase membrane fluidity and aerobic and fatty acid oxidative enzymes in the flight muscles, which enables prolonged endurance flight. Support for this hypothesis is mixed, and there is no empirical evidence for increased flight performance. We fed yellow-rumped warblers ( Setophaga coronata coronata) diets enriched in either n-3 or n-6 long-chain PUFA or low in long-chain PUFA and evaluated flight muscle metabolism and endurance performance in a wind tunnel flights lasting up to 6 h. Fatty acid profiles of muscle phospholipids confirmed enrichment of the targeted dietary fatty acids, whereas less substantial differences were observed in adipose triacylglycerol. Contrary to the predictions, feeding n-3 PUFA decreased peroxisome proliferator-activated receptors-β mRNA abundance and muscle oxidative enzyme activities. However, changes in muscle metabolism were not reflected in whole animal performance. No differences were observed in flight performance among diet treatments in terms of endurance capacity, energy costs, or fuel composition. These measures of flight performance were more strongly influenced by body mass and flight duration. Overall, we found no support for the natural doping hypothesis in a songbird. Furthermore, we caution against extending changes in flight muscle metabolic enzymes or fatty acid composition to changes to migratory performance without empirical evidence.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".