usdalegl.htm; USPHS, 1996). This facilitates a productive, cooperative climate at the 
institution as well as a more in-depth consideration of animal welfare issues. 
At the same time, investigators recognize that progress in veterinary medicine brings advances 
to the laboratory that can improve an animal's health and welfare and the success rate of a 
particular experimental approach. Nevertheless, the principal investigator's training and track 
record should be considered when committees and veterinarians evaluate the proposals. 
Those with extensive experience may well be the most knowledgeable consultants about the 
behavioral needs and capabilities of a particular species. Long experience of investigators 
with a particular technique or preparation can provide insights into the type of care that is 
most appropriate, particularly for uncommon species or highly specialized research. 
Conversely, investigators who have conducted similar experiments for many years may benefit 
from being apprised of advances in fields that can enhance their research. In other words, all 
partners in the enterprise must be willing to acknowledge the limits of their expertise and to 
be open to additional sources of information. 
Science demands investigation at the edges of human knowledge. This means that the ability 
to innovate and to ask questions for which the answer is not known is necessary for scientific 
progress. The USDA animal welfare regulations, the USPHS Policy, and the Institute for 
Laboratory Animal Research Guide for the Care and Use of Laboratory Animals (ILAR, 1996) 
all allow lACUCs to permit exceptions to guidelines under certain circumstances and if 
appropriately justified. This handbook, therefore, is intended to suggest factors that lACUCs 
can take into consideration when reviewing protocols for research to avoid being 
unnecessarily restrictive. Of course, no set of standards, guidelines, or considerations can be 
viewed as fixed: New circumstances, knowledge, and values must be incorporated into our 
judgments. 
Each LACUC has to make an informed decision in all cases as to when a study may be at the 
limits of what is considered acceptable. Questions to be answered in these circumstances: Are 
there alternatives? Can the study be refined to reduce pain or distress further or to reduce the 
number of animals? If not, can the proposed study provide an answer to an important 
question? 
Finally, both investigators and lACUCs should be aware of public perceptions and of the 
public's need to be educated by informed explanations on the use of animals. Research on 
animals is conducted largely through public support, financially and politically. This involves 
a level of trust that can be maintained only if information on the appropriateness, the 
benefits, and the attention to animal welfare that go into animal research is readily available 
and acceptable. ■ 
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