It depends on the specific problems of the individual dog. Remember supplements and food are not medication, so at best, it’s hit or miss. They don’t have to be regulated by the FDA
I like to add fish oil and glucosamine to my old guy’s water soaked kibble because he shows signs of arthritis and has dry skin, potassium citrate, because he has a history of bladder stones.
To get specific advice and dose recommendations, I would consult a homeopathic vet.
Otherwise, it’s just a guessing game, or see a veterinarian that specializes in geriatric issues, there may be prescription medication that can keep your seniors comfortable.
PS: I have never given milk thistle to my pets, I took it myself once years ago, I forget why…but I think it made me sick…
