I personally don't see any problem with that. In genetics or pharmacology, outbred strains such as CD-1 are sometimes a problem because of their heterogeneity. However for a behavioral study I don't think this would be a problem. Their behavior might vary more between individuals than, say, BL/6 mice, but that variation can be interesting in itself. Just use a sufficient n.

animal behavior is regulated through gene. This why pure bread  animal is recomonded  for explanation of result so that extrapolation of observation can be used  for human. to do experiment no harm. but clinical experience must be from pure bread. However your result may be more useful then pure bread. pcg,CLi,Mumbai

There is certainly nothing wrong with using an outbred strain for behavioral studies, though as already noted above, you may see more variation than what you would observe from an inbred strain. The more important question is whether the CD-1 strain is appropriate for the question you're asking. We would need a bit more detail on your project to directly answer that, but a few things to consider: First, remember that variability will significantly alter your significance in behavioral studies, so a heterogeneous strain may require you to use a greater number of animals (which of course comes with it's own set of issues such as compliance with your IACUC and money for animals, etc). Second, if you're planning to look at anything mechanistic (such as molecular pathways) it would be better to use an inbred strain where there are fewer variables; this is particularly true if you plan to look at a drug treatment or other type of intervention

Thank you fellow contributors! I am grateful for all the advice and suggestion offered thus far. They are very helpful.

As for my research, I'm interested in understanding how focal malformation in cortical development contribute to neurodevelopmental disorders like autism. We manipulate neuronal gene expression profile using viral vectors, and therefore do not necessarily need a homogeneous genetic background offered by an inbred strain. On the contrary, the model would be more reflective of the human population and perhaps more robust, if it were constructed using an outbred strain. However, I may be too naive in my thinking and would love your inputs and perspectives.

Considering the translational perspective of you research, in my view an outbred strain should be preferred over inbred.

Dear Lawrence,

I totally agree with Sakire comment. Commonly, studies with transgenic mice are done with an inbred strain (mainly C57BL6/J) to reduce variability. But exactly for studies in which you want to model a human disease you want to be sure that the effects of the genetic manipulation are stronger that interindividual variability (humans are surely no inbred animals!). Moreover, CD-1 mice are excellent breeders (litter size between 12-16), that is a great advantage for breeding transgenic mice because you always have all genotypes represented in both genders. This is the reason why we backcrossed some of our transgenic mice (that had a C57BL/6J genetic background) into CD-1 mice and we were very happy to see that the phenotype of the mutant mice had 100% penetrance also with CD-1 mice. The same holds true if you want to do pharmacological studies: is it the correct decision to use an inbred strain with the risk that the results are strain specific? In my opinion the answer is no. At the beginning of a study it make sense to use only one strain, but then you should confirm the results with other strains or even better with an outbred strain.

Also, the homogeneity of the behavior within an inbred strain is sometime overestimated. We had two studies showing that even C57BL/6J mice show enormous inter-individual variability in their coping strategies and gene expression (Jakovcevski et al.,Neuropharmacology 2011, 61:1297-1305; Jakovcevski et al. Genes Brain Behav 2008, 7:235-243).

Finally, CD-1 mice are very good for behavioral studies in general. Their ethogram is, among many mouse strains, very similar to that of wild mice, in particular for their social behavior (Parmigiani et al., Neurosci Biobehav Rev 1998, 23:143-153 ). They also perform extremely well in spatial learning tasks, meaning that they still see well despite they are albinos (I tested it in person: Fellini and Morellini, J Neurosci 2013;33:1038-1043; Fellini and Morellini, Behav Brain Res 2011, 222:380-384).

Best regards,

Fabio

If I can add starting from outbred genes and inbreeding them according to the behavioral performances on the EPM helped out to identify susceptibility genes for anxiety and comorbid disorder. The model was established at the MPI Munich and lead to notable publications in the behavioral field of affective disorders. The model is called HAB, NAB,LAB standing for high, normal and low anxiety-related behavior, respectively.

I totally agree with Fabio Morellini's comments. People often forget that using inbred mice for decreasing variability is done at the cost of the generalisability of the results.

I also agree that behaviorally inbred mice are not necessarily less variable than outbred mice. For example, we have often observed that the variability in locomotor activity is similar in C57 and Swiss mice.

So if the CD1 mice work with your behavioral tests, I encourage you to stick with them.

Thanks again everyone for weighing in on the matter. I certainly have learned a great deal about behavior neuroscience from this forum. I shall follow the recommendation from the majority and continue  my behavior experiments with CD-1 mice.

Dear Madam

For doing experiment with out bread animal  it is nothing wrong. Negative result is also is scientific work can be a mile stone for future research.Extrapolation to human is questionable that is why inbred preferred. hope It is clear now with kind regards

Hi everyone,

Seeing that some people are still reading this question and answer thread, I figure an update is in order.

Last year (2017), we followed up this question with a series of studies and subsequent publication of our findings, which can be found here Article Outbred CD1 mice are as suitable as inbred C57BL/6J mice in ...

In short, we concluded that CD1 outbred animals are also suitable for social behavior tasks, with a few caveats. The main caveat being that CD1 behavior is more variable, and lower powered, when compared to C57 animals. The other being the acclimation paradigm of CD1 -- in a three chamber sociability task -- is different from that of C57 animals.

I just want to say thank you to those who weighed in on this issue. We could not have done this without you.

With gratitude,

Lawrence

Of course it is good to use out-bred strains of mice. Inbreds do always have some problems that went with the inbreeding. We used our swiss albino outbred as a normal strain and control group for our selections: