Peter,There is no need to remove any of the bones and no need to rinse. Unlike the brine in Jack Mackerel and canned sardines you can give them the liquid in the can as well.
The water in the sardine cans is brine, water saturated with salt, and may cause excessive thirst (although that can be hard to tell with a Newf) and in some cases results in loose stools. This is more of a problem with the 15 oz cans of Jack Mackerel which has only 10 oz of fish and five ounces of brine. If you are using the 4 oz cans of sardines, then the amount of brine may be insignificant.Peter,
What's wrong with the liquid in canned Sardines? I regularly feed Sardines packed in water and pour the entire contents into Oliver's bowl.