1. Whole blood can be used to gain insights on several molecular mechanisms involved in animal physiology. However, its use to extract RNA from organisms that carry nucleated red blood cells is limited due to its high nuclease content and instability under field conditions.
2. Here, we evaluate three commercially available RNA preservation and extraction methods applied to avian whole-blood samples kept in different storage conditions to identify the most suitable ones for use in field studies.
3. Whole-blood starting volume was the most important factor; only samples with a starting volume of 50 µl yielded RNA, whereas all 100 µl samples failed to provide any RNA regardless of the method used. RNA concentration decreased with storage time in every method employed. Samples stored at -20°C yielded higher RNA concentration than the ones stored at 4°C, although some possible effects of freeze-thaw cycles were observed.
4. For two of the three methods, it is likely that DNA contamination and/or extensive degradation of RNA could have taken place. Only whole blood stored and extracted using the Quick RNA Whole Blood kit provided high-quality RNA in every condition tested.
Keywords: Gene expression; RNA extraction; RNA preservation; birds; field sampling.