A non-invasive method in rodents for assessing health and establishing endpoints for adults where body weight is not a viable monitoring tool, such as with tumorTumor Neoplasm, new growth. Is predicated upon autonomous growth of cells or tissues into benign or malignant tumors. models, ascitesAscites An accumulation of fluid in the abdominal cavity, for instance as a result of a tumor mass. By injecting cells that produce antibodies (hybridoma cells) into the abdominal cavity, monoclonal antibodies can be harvested from the ascites thus induced, but this method is prohibited or discouraged in several European countries because in vitro antibody production is a good alternative. production and pregnancy, or young growing animals.