More thoughts:

1.) Gravel does like to eventually sink through soft mud and disappear. You might want to put down some tough landscape fabric first to prevent your gravel from sinking. I think cattle hooves will probably punch some holes or crescents in your fabric. Even so, I think it would still be a good investment in time/money to use the fabric as part of your long term solution.

2.) Lots of threads on Pond Boss about beach sand placed on a sloping shore tending to migrate into deeper water. If you ever get a very low water level in your main lake, then you might use that opportunity to build a ledge or berm a bit offshore (at normal pool) of your cattle bank. That should slow your rate of gravel working down the slope due to the action of the cattle.