An exchange of views on culling.

In two articles in this issue (Fundam. Appl. Toxicol. 37, 2 -6 and 7-22), we present something new: two papers on the opposite sides of an argument. In this case, the argument regards culling of litters. For many scientists performing breeding studies in a regulatory context, the culling of litters to a standard size shortly after birth (generally 3-5/gender/ litter) is an accepted practice. While the origins of this practice seem to be lost in the mists of time, the perceived benefits (reduced manpower requirements, likely reductions in variations in pup growth rates due solely to litter size differences) appear to justify the random discarding of some animals. This is especially true when the adverse effects of culling are far less obvious.