Sir

C. Jimenez, in Correspondence, considers that detailed information on the way animals are handled and treated should not be placed in published papers (Nature 447, 259; doi:10.1038/447259b 2007).

I disagree, because it is a fundamental principle of the scientific process that when a paper is published, the study can be repeated from the description given in the methods, thereby allowing external validity to be assessed. To this end, variables that might affect the results need to be reported accurately.

It is well-documented that making even a slight change to a laboratory animal's environment or husbandry can have profound influences on its biological functioning. Cage size can influence metabolism, baseline rectal temperature, the fever response, feeding behaviour and behavioural responses in predator–prey interactions. The type of flooring in a cage can affect blood pressure, heart rate and body temperature. Other factors that influence physiology and behaviour include housing laboratory mice as singletons or pairs, the complexity of the cage and the extent to which animals are handled.

Variables such as these, which might be changed to improve the welfare of the animals, should be reported in published papers as an essential component of the accurate reporting of science.