exceed 0.5 ml per 100 g bird. If repeated sampling is necessary, sampling sites
can be changed, for example, alternating between the ulnar vein of the left and
right wings. Repeated sampling from the same site may damage the vein or even
cause it to become occluded, leading to necrosis. Lubjuhn et al. (1998) found
that blood sampling free-living Great Tits Parus majorhad no effect on survival
or breeding success.
Venepuncture can be used to provide a blood sample for DNA extraction for
molecular studies. However, current technology permits the use of very small sam-
ples, and sufficient can often be obtained from the base of a feather plucked during
molt, when the feather is still growing. This is clearly quicker and less traumatic, but,
in the United Kingdom, this still requires licensing if it is for a scientific purpose.
Techniques in modern physiology and genetics can require biopsy of any
of several tissues. Those most commonly sampled (in addition to blood) are
adipose tissue, muscle, liver, and gonad. Such biopsies require surgery and hence
anesthesia (see below).
9.2.6Administration of substances
There are four commonly used routes for substance administration (Morton
et al. 2001). Substances can be administered orally if this is appropriate. Ideally
this can be done by dissolving the substance in drinking water or mixing with
food. In cases where a precise dose is required, for example, toxicological studies,
oral gavage (inserting directly to stomach through a tube) may be necessary. In
this case, care must be taken to avoid obstructing the trachea. The recommended
maximum dose is 10 ml kg^1 body weight.
Intravenous injection. The veins that can be used are the same as for blood
sampling, that is, the right jugular vein, the ulnar vein, and the medial metatarsal
vein. Choice will depend largely on the size of the bird. The maximum injected
volume is 5 ml kg^1.
Subcutaneous injection. This is particularly suitable for birds because the skin
is only loosely attached to underlying tissue, and the loose skin at the nape of the
neck is an ideal site. Maximum volume is 2–5 ml kg^1.
Intramuscular injection. Ideally, this should only be used if other routes are
inappropriate. Intramuscular injections can be painful and they can lead to
bleeding and may cause necrosis. Care must be taken to avoid nerves and blood
vessels. Maximum volume is 0.05 ml kg^1.
Intraperitoneal injections. This should be avoided in birds because substances
are likely to enter the air sacs and so may affect respiration.
218 |Techniques in physiology and genetics