However, since Sprague Dawley rats are known to grow tumors at a high (and very variable) rate, the study was considered flawed in design and its findings unsubstantiated
Dear Ahmed,
the choice between SD and Wistar Rats is an ongoing discussion for ages. The US has long preferred SD, Europe Waistar rats, both out of mostly scientific traditions. Both strains have their pros and cons:
SD- larger litters but less favourable maternal behaviour, tend to show more agressive behaviour
Wistar - docile, great for reprotox, tend to get fat with age with all associated consequences
As both are inbred strains, the genetic pool for both is limited (giving less statistical variance but higher prevalence for certain neoplasias as wildtypes/outbred strains).
Depending on your desired study type, my personal preference from experience would always tend towards Wistar rats. But that is prejudieced, I am European ;-).
I hope that helped a little bit
Best regards
Geertje
Toxicity and tumorogenicity are two different concepts. If you are looking at acute/subacute toxic effects then either strain is fine. SD rats do have some tumors that develop but are typically only seen at ages >14 mo. Wistars have there own set of tumors that appear, also at advanced age. So use of either strain in animals under 12 mo of age should not be compromised by tumor generation. Further, ALL such studies should have control group that will account for such secondary factors and therefore allow you to evaluate pesticides. We do this all the time in 2 yr carcinogenicity studies for drug and other compounds in both SD and Wistar and can read results through background tumor development.
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