How does Candy's dog and his fate foreshadow other events?

Candy's dog was once very helpful on the farm, but due to his old age he now has nothing to offer the branch. This is similar to Candy himself, who recognises he is increasingly becoming less useful and will no longer be needed at the branch. Candy cannot bare to part with the companion he has had since a small pup, yet despite his best efforts Curly shoots the dog.
This foreshadows the fate of Lennie, how he is also a great, albeit hindernig, companion to George, he will eventually have to be put down due to his inability and accidental murdering of Curly's wife. Candy regrets not killing the dog himself, and Lennie, like the dog, is due to be 'put down' by Curly. These events foreshadow George's decision to shoot Lennie himself in the most humane manner possible.