I can try, but I have never actually treated rats with silymarin - we thought about it, but it in initial cell culture experiments, it did not help to answer the questions we were trying to answer, so we never got to animal studies.
There are reference where it has been used in dogs - I think that I would modify what was done in dogs, but you may have to optimize the dose for rats - differing metabolic rates and all that.
In fact, my colleague at the laboatory used to administre sylimarin via orally route to their wistar rats, but sylimarin is very difficult to mixed even with water, it stay biphasique although a long period of homogeneization, so you have to agitate it for long times (30 minute or more)before an orally administaration . Conerning the dose i will ask them.