Testing for possible effects of cedar wood shavings and diet on occurrence of mammary gland tumors and hepatomas in C3H-A-vy and C3H-Avy-fB mice.

C3H-A-vy and C3H-A-VY-FB mice transferred from our colony to the laboratory of Dr. J. R. Sabine in Australia had a markedly reduced incidence of both hepatomas and mammary tumors. Sabine and co-workers (J Natl Cancer Inst 50: 1237-1242, 1973) attributed the low incidence of tumors in their laboratory compared to the high incidence in this laboratory to the fact that we routinely use red cedar shavings in the bedding, whereas they use sawdust, predominantly Doublas fir. Results of tests in this laboratory showed that the difference in occurrence of tumors could not be attributed directly to either a difference in diet or bedding. There was no evidence that the cedar shavings were carcinogenic. The animals in Australia on bedding without cedar shavings were not as healthy as our animals, in that they did not grow as well and were infested with ectoparasites; apparently these factors caused the reduced occurrence of tumors.