A lifetime of inescapable fear, pain and stress
Many people connect closely with a companion animal at some point in their lives – usually a cat or dog – but sometimes it may be another animal, like a rat or guinea pig. Through these interactions we become keenly aware of an animal's great capacity to feel pain or discomfort, and to experience a full range of emotions – joy, love, fulfillment, terror or fear.
Yet society routinely denies this happens to animals used in research. We hear about "purpose bred" animals, as if they were some special breed of robotic animal, devoid of sensation or emotion, and about the great attention from scientists and government to the care and protection of laboratory animals. This is all designed to make people feel better about the suffering of animals in laboratories. We are made to picture comfortable housing facilities, content, healthy animals, and committees of professionals who make sure that there is little or no suffering.
Minimal protection for animals in labs
The Animal Welfare Act (AWA) is the primary federal law covering laboratory animals in the United States. But most people are not aware that there is no provision in the AWA that restricts what can be done to an animal during a study. It only applies to the type of care an animal receives before and after experimentation. There is nothing in the language of the AWA that prohibits what can be done to animals in the course of the experiment. That is left up to the researcher who may be restricted by the oversight committee, though this is rarely done. Oversight committees typically approve the vast number of research procedures and have been criticized by the Office of the Inspector General for failing to provide adequate oversight by not effectively monitoring animal care activities or reviewing protocols. As a result, animals are frequently subjected to prolonged suffering in experiments that inflict significant pain and distress.
Further narrowing the scope of its protection, the Animal Welfare Act only applies to a limited number of species, omitting a massive 98 percent of animals, including rats, mice and birds, who are unjustifiably excluded from any federal regulation. The 98 percent figure is an estimate, because without legal protection, there is no requirement for laboratories to keep counts, or release records, on the numbers of animals in this category.
The animal research industry typically asserts that it is fully regulated as proof that animals do not suffer in laboratories. However, closer scrutiny of the oversight reveals a system that is laden with problems, the most serious of which is the standard policy of allowing research institutions to regulate themselves. Self-regulation applies to all types of procedures, the level of pain and illness inflicted, and the living conditions of the animals.
Frequent violations of the Animal Welfare Act are documented in government inspection reports, and a disturbing number of undercover investigations and whistleblowers have exposed a great deal of negligence and suffering that affects animals used in experiments.
Animals used in research laboratories undergo considerable pain and distress from frequent routines and procedures that are capable of creating pain. It is impossible to detail the full range of things that are done to animals in the course of experiments, but without any restrictions, the range is boundless, immeasurable and chilling.
One type of common experiment is drug and chemical testing, which typically results in immense suffering for animals. The U.S. Food and Drug Administration requires that all drugs be tested on animals, even those that are developed with non-animal technologies. Combined with the chemical and products industries, this results in millions of animals subjected to such experiments.
The LD50, a standard test used in toxicity research, is so named because it administers the test dose in consecutive, increasing doses until 50 percent of the animals in the trial die.
Death by poisoning is unquestionably extremely cruel. To give some idea of what animals experience during these tests, consider this listing that scientists have published as common clinical signs indicating an animal is in distress: Gasping, difficulty breathing, tremor, seizures, abnormal vocalization (crying), diarrhea, vomiting, bleeding from any orifice, edema, abdominal rigidity, rectal or vaginal prolapse, swollen joints, and paralysis. 
Not only do animals suffer from the effects of the drugs or chemicals, but research has shown that just the experience of being force-fed the test substance can result in extreme distress. The procedure typically used to administer the test dose directly into the animal’s stomach is called gavage. The gavage procedure involves forcibly restraining the animal, followed by insertion of a long, thin tube that is passed into the mouth, esophagus and then stomach. During a testing trial, this procedure can happen multiple times a day over a period of days or weeks.
Complications from gavage are numerous and significant, including accidental administration of the test substance into the trachea and lungs, aspiration pneumonia, esophageal trauma or perforation, abdominal bloating, fluid in the lungs, the accumulation of blood outside the lung, and death. 
Research has shown that just the stress of the procedure alone may result in bodily harm. One study compared a group of rats who were gavaged for 10 days with just the tube alone and no test substance with another group who were dosed using gavage for 10 days with a test substance (cyproterone acetate). After the 10 day trial, both groups of rats exhibited massive liver disease, suggesting that the gavage procedure alone, and not the test chemical, was responsible for the resulting pathology. 
This single, striking example of what animals may often experience during a typical toxicity test demonstrates how profound and persistent their suffering can be.
 OECD [Organisation for Economic Co-operation and Development]. 2000. Guidance Document on the Recognition, Assessment, and Use of Clinical Signs as Humane Endpoints for Experimental Animals Used in Safety Evaluation
 Balcombe JP, Barnard N, Sandusky C (2004). Laboratory routines cause animal stress. Contemporary Topics in Laboratory Animal Science 43:42-51.
 Roberts, R.A., Soames, A.R., James, N.H., et al. (1995) Dosing-induced stress causes hepatocyte apoptosis in rats primed by the rodent nongenotoxic hepatocarcingen cyproterone acetate. Toxicol. Appl. Pharmacol. 135:192-9.