Small animals as experimental models

Animal models can prove invaluable in predicting outcomes of human surgical procedures and medical interventions. Clearly the closer the anatomic and physiological similarity between the studied animal species and human, the more closely the animal model will mirror outcomes in people. Often non-human primates will most closely approximate results in humans. Nonetheless, ethical and economic concerns regarding these large animal models mean that small animal models retain strong utility. Generally speaking, large animal models are reserved for final pre-clinical toxicity and efficacy studies, with all preliminary studies conducted in small animal models. Small animals used in experimental surgery chiefly consist of mammals - rodents (mouse, rat, guinea pig and hamster) and rabbits. Mice are most commonly used because of their economy, rapid breeding cycle, ease of handling, and availability of inbred strains and genetically modified strains. The large animals (chiefly non-human primate, dog and pig) will be covered in next chapter. The principles of the three R's: refine (less suffering,), reduce (lower animal numbers) and replace (alternative in vitro assays) must be applied in all small animal experiments. Well-designed animal model experiments have allowed us to develop the surgical techniques currently available for treating patients. In this chapter, we examine background to the common small animal models and practical aspects used in experimental surgery. We also look at the utility and limitations of small animal model surgery.