Antisera can be raised on a wide variety of vertebrate animals: mice, rats, guinea pigs, hamsters, rabbits, chickens, sheep, pigs, goats, donkeys, and horses. The choice of animal for immunization tends to be determined by the amount of serum that is needed, the amount of antigen available, and the degree of the strangeness of the antigen to the immunizing animal.
Sheep, goats, pigs, donkeys, and horses produce larger amounts of antiserum, but they are expensive to maintain and are generally used only for the production of commercially available antisera. Rabbits are most often used in the laboratory setting when individual researchers need to generate larger volumes of a particular antiserum.
Exsanguination is the recommended method for collecting large amounts of antiserum from an animal for slaughter, but this should only be performed by persons well versed in the correct technique and as approved by national and institutional guidelines. The production of limited amounts of antisera in the mouse can be overcome by the production of ascites fluid in which high antibody titers, equivalent to those achieved in serum, can be obtained. When only small amounts of antigen are available, the use of mice is also a clear advantage.
An additional advantage is that most researchers use inbred mouse strains and the genetics of the immune response for most strains has been well documented. If a weak response to an antigen is obtained in a particular mouse strain, changing the strain can help overcome the problem. If the amount of antigen is not limiting, multiple animals should be used since, even in inbred animal strains, a single antigen preparation will produce different responses.
The most important rule in the choice of animals is that immunization should be carried out in the animals that are at the greatest evolutionary distance from the antigen source.