Knockout Rat Phenotype Database?
Opinion:

the Jackson laboratory

http://jaxmice.jax.org/

Is the industry leader in transgenic mouse production. Their list of mouse strains is almost a db in itself but currently no db exists that I'm aware of. I take it your looking for something similar to what's available for c elegans:

http://www.celeganskoconsortium.omrf.org/