Variation in postsampling treatment of avian blood affects ecophysiological interpretations

Abstract

Summary1. The fluid component of blood is widely used in ecophysiological investigations, including measures of immune function and stable isotope ecology. After blood collection, delayed separation of blood extracellular fluids from red blood cells is known to affect the concentration of a wide range of biochemical compounds in the resulting fluid, as does prevention of clotting (producing plasma) when compared with blood allowed to clot (producing serum). 2. One challenge when investigating immune function and stable isotope ecology, therefore, is discriminating variation because of the effect of the biological factors of interest from potential methodological artefacts. This study assesses how seven widely used measures of immune function and stable isotope composition respond both to delayed separation of the cellular and fluid components and to the clotting of blood samples from two species of waterfowl. 3. Samples that remained uncentrifuged for up to 12 h did not differ from those centrifuged within 15 min of sampling from the same individuals, indicating that samples from a wide range of field conditions may remain highly comparable. However, the outcome of three of the four immunological assays and two of the three isotopic analyses was highly dependent on the type of fluid, with higher immunological activity and higher relative concentrations of heavy carbon and total nitrogen in plasma compared to serum. 4. Researchers interested in immune function and stable isotope ecology may obtain the most useful results by ensuring that they use a single fluid type in their investigations.

Cheetahs have a stronger constitutive innate immunity than leopards

“…Results of immunological tests conducted with serum and plasma from whole blood centrifuged after 2 hours, 4 hours, 6 hours and 12 hours from blood collection and after 2 hours and 4 hours from blood collection, respectively, do not differ100. There was no systematic bias for samples centrifuged later than 12 h after sampling, thus all samples were included for immunological tests.…”

Juveniles and migrants as drivers for seasonal epizootics of avian influenza virus

“…Blood samples were allowed to clot for c . 6 h before being centrifuged in order to separate serum from red blood cells (Hoye ). Serum samples were stored at −20 °C until analysis.…”

Common measures of immune function vary with time of day and sampling protocol in five passerine species

“…The time between capture and collection of a blood sample was measured as the time elapsed between when the bird was observed to enter the mist net and the time that collection of the blood sample was completed. Each sample was kept on ice until it was centrifuged, and the plasma was collected and frozen; for each sample, plasma was collected within 10 h of blood sample collection in order to minimize introduction of measurement artifacts as a result of sample handling (Hoye, 2012). I used handling time (time elapsed between capture and obtaining a blood sample) as a proxy for handling stress.…”

“…It will be important to conduct similar studies in a range of species from a variety of habitats, as well as examining how factors such as life history, breeding status, age or time of year may alter the variation in immune function documented here. In addition to the recommendations outlined below, researchers should keep in mind that measures of immune function have been shown to vary between plasma and serum samples, and that periods of greater than 12 h between blood collection and plasma or serum collection may also impact immune measurements (Hoye, 2012). Natural antibodies and complement are both easily measured with a single assay (Matson et al, 2006).…”