Many of the above have worked for me in the past. I do avoid animal fats if there is a puppy or dog that likes to chew, nearby
Can you blame a pup? First off, it is leather, and leather is great for teething. Secondly, they smell intensely of the person they love. It's too much to ask of a pup to understand that they gotta leave 'em alone, so you gotta be the responsible party.
I use mink on my expensive, high quality moccasins. When they have been dampened, I wear 'em until they are dry and then rub in generous amounts of grease, paying extra attention to any raw edges of the leather and the seams. I practically putty knife it there and then use a hair dryer to warm the grease and leather until it melts in. I do pretty much the same for boots.