Estimating attrition of Sprague Dawley rats for the establishment of an oxygen-glucose deprivation model

Abstract

Abstract The use of laboratory animals for biomedical research is strictly regulated to prevent their suffering and inadequate use. The 3 R’s principle, established the framework on the use of animals for scientific research, following the concepts of replacement, reduction, and refinement. While experimentation is in process, attrition usually can increase the number of animals needed to achieve the proposed objectives. Unfortunately, attrition or incidents concerning the final sample size are seldom explicitly shared in the literature. In the present study, we designed experiments to develop a protocol for primary cortical cell culture and to establish the first in vitro brain ischemia model in Panama. Here we report the effects of attrition in the final number of animals used for experimentation. Primary cortical cell cultures were produced from 17-day Sprague-Dawley rat embryos. Vaginal cytology was used to evaluate oestrus cycle and to identify copulation signs. Pregnant rats had routine evaluation plus clinical/weight follow up every week before euthanasia, at day 17. Sample size calculations estimated 26 rats for the study using a theoretical attrition rate of 25%. The final number of animals used empirically was 26; however, the measured attrition was 50% (13). The incidents related to attrition were categorized in mating problems, pregnancy complications, reduced number of embryos produced and in vitro experimentation failures. These results highlight the importance of calculating attrition for studies requiring laboratory animals, taking in consideration the context and available data from local institutions to allow for the most efficient use of laboratory animals, especially for newly established laboratories in developing countries.