John Steinbeck's Of Mice and Men is a novella about fraternity, loyalty, and friendship. Readers can identify numerous relationships which illustrate both good friendships (as between Lennie and George) and bad "friendships" (as between Candy and Carlson). Readers are even shown loyalty between man and dog (as with Candy and his dog).
Candy, an old rancher, has a dog which is rather "ancient." Some of the other ranchers cannot fathom what keeps Candy from putting down a dog who cannot walk and "stinks like Hell." Candy, having the dog since it was a pup, does not give in easily when Carlson suggests shooting the dog. It is not until Slim, the most respected man on the ranch, agrees with Carlson (that putting the dog down would be best) that Candy gives in. Up until this point, Candy remained loyal to his dog. It was only the thought that this was best for the dog that allowed Candy to agree to put him down (kill him).
Slim, on the other hand, does not show any real loyalty to his own dog. In fact, the only time his dog is mentioned is when it has puppies and suggestions are made regarding giving Lennie and Candy pups. Slim shows no attachment to his dog or its pups. He readily agrees to give them away without any thought at all.