Formulating the Question
It may help to think of your research question in four parts. Leenaars, et al. suggest four components for a focused research question in the field of animal research:
2.) Disease of interest/health problem
3.) Animal/animal species/population
4.) Outcome measures
A research question including these concepts could be formatted as "What is the effect of [intervention/exposure] on [outcome measures] in [animal species/population] for [disease/health problem]?"
It may be useful to first determine what keywords specific to your research protocol are necessary, and then to add keywords for the reduction, refinement, or replacement of animal research subjects (the "Three R's").
Tips for Research-Specific Keywords
Leenaars, M., Hooijmans, C., van Veggel, N., ter Riet, G., Leeflang, M., Hooft, L., van der Wilt, G.J., Tillema, A., and Ritskes-Hoitinga, M. (2012). A step-by-step guide to systematically identify all relevant animal studies. Laboratory Animals, 46(1), 24-31. doi:10.1258/la.2011.011087