2.7 Manipulative Procedures: Tissue Sampling, Injections and Implants
Only trained, experienced personnel should take tissue or blood samples from live mammals. The use of local or general anaesthetics may be required if the anticipated pain from the procedure is more than mild or momentary. Investigators should develop a sampling protocol, including sample processing and storage, prior to commencing the study to ensure that appropriate samples are taken, the opportunities are maximized and waste is minimized.
The estimation of mammal age can be made by examination of antlers, horns or dental eruption and wear, although for some studies, cementum analysis is required for accuracy. The specific tooth most suitable for cementum analysis may vary with species; however, vestigial teeth such as maxillary premolars are usually extracted. These teeth generally have short roots and can be removed quickly with experience and the appropriate instruments. The removal of permanent incisors in ungulates is extremely painful due to large nerve roots and can subsequently impair feeding on a permanent basis. The scientific literature favourably compares the estimation of age by non-invasive techniques and cementum analysis in ungulates, thus removing the necessity for incisor removal. Extraction of these teeth should only be done, if justified by review, by experienced personnel and with full analgesia under general or local anaesthesia.
The most common method for the collection of blood from mammals is venipuncture. Many sites are accessible, but preferred veins vary with species (e.g., femoral vein in bears, cephalic or jugular in cervids). Blood may be withdrawn by needle and syringe and decanted into blood tubes or removed directly into blood tubes using double ended needles. Training and experience in venipuncture can ensure a rapid and painless procedure.
In general, it is advised that no more than 10 - 20 % of the animal's blood volume (approximately 1.5 - 2.5 % of lean body mass) be collected during sampling. Following blood sampling, hemostasis can usually be achieved by applying direct digital pressure to the collection site for several minutes. The bleeding should stop before the animal is released.
Proper processing and storage of blood samples is vital to ensure its subsequent analysis. Investigators should contact a veterinarian and/or a laboratory for recommended techniques.
In addition to blood, study protocols may require the collection or biopsy of other tissues such as fat, muscle, liver, and skin. Before initiating a project involving invasive biopsy techniques, the researcher should conduct an adequate peer and literature review. Investigators should only collect the minimum amount of tissue that is necessary to reliably satisfy the research goals. In some instances, analgesia or anaesthesia may be required to effectively and humanely obtain the necessary sample. The survival of animals that are released following a biopsy procedure should not be compromised. It should be noted that non-invasive sampling is the preferred alternative.
Diet information may be gathered as part of ecological and nutritional studies. The sacrifice of animals for stomach contents is rarely justified. Instead, it is preferable to collect prey remains or fecal material for analysis.
Injections of appropriate solutions, whether subcutaneous, intramuscular, intraperitoneal or intravascular, may usually be made with very little effect on survival or normal animal behaviour. The personnel performing these procedures should be properly trained. Some solutions may be irritating or dangerous to the subject if they are not properly injected. Implants may require major surgery under general anaesthesia and may migrate or become inactive if they are not properly inserted. Proper sterile procedures are required for intraperitoneal transplants.
Before being used in the field, it is strongly recommended that new techniques are evaluated on captive individuals. A review of the pertinent literature will help to identify any potential adverse effects that injections or implants may have upon the behaviour, survival and well-being of the study animals.
When performing major manipulative procedures, humane principles should always be the first priority. There is no justification for accepting substandard care of study animals due to a lack of knowledge or expertise.
The conditions governing the choice of procedures may depend upon the intended fate of the subject. In general, four categories of subjects can be distinguished:
For any animal that is to be released to the wild, the prime consideration should be that the procedure will have a minimal effect on its subsequent survival and reproductive potential. No animal should be released to the wild until it is deemed to be sufficiently recovered to perform normal behaviours, including predator evasion and feeding. If the purpose of the experiment is to alter survivability or reproductive potential, then the interference should be no more than is necessary, as judged by the investigator, to test the issue in question. Even animals that are to be held as permanent captives or ultimately euthanized should not be subjected to pain or suffering.
The acceptability and practicality of a procedure will vary with the experience and skill of the investigator. Procedures should only be performed after consultation with and preferably under the guidance of an experienced wildlife veterinarian. For any invasive procedure that is more complicated than a simple injection there should be supervised practice on a model or a carcass before it is attempted on a living subject. The ultimate goal of practice is to be able to perform the technique quickly and efficiently with minimal tissue trauma.
A major portion of surgical trauma for many wild animals is the physical or chemical restraint that is associated with the procedure. Anaesthesia can be physiologically stressful and many animals are severely stressed by prolonged handling. Therefore, a technique will be more successful if it can be performed rapidly, but not hastily. Invasive procedures, if performed correctly, need not affect the survival or reproductive potential of the subject.
Whenever it is practical, researchers should release field trapped animals following the completion of their studies. However, there are exceptions to this and, as a general rule, field trapped animals should be released only:
Captive animals that cannot be released should, whenever possible, be distributed to colleagues for further study. However, if the animal is in chronic distress or pain, or if release or rehabilitation is neither feasible nor likely to succeed, then euthanasia may be the only alternative. If animals must be destroyed subsequent to a study, then it should be done using a method of euthanasia which is humane, instantaneous and considered acceptable (see Reference section). In addition, the method of euthanasia should not interfere with any future research potential of the carcass or any specific post mortem analyses. In both the field and the laboratory, the investigator must be careful to ensure that euthanized animals are dead before disposal. Disposal of carcasses must be in accordance with acceptable practices as required by municipal or institutional regulations. Animals containing toxic substances or drugs should not be disposed of in areas where they may be scavenged or become part of the natural food chain.