What is the symbolism of the death of Candy's dog in John Steinbeck's 'Of Mice and Men'?

In John Steinbeck's novel 'Of Mice and Men', the death of Candy's dog symbolises the loneliness of the ranch workers, and demonstrates that there is no place for affection or sentimentality in their lives. Early on in the novel, George states that men who work on ranches are the 'loneliest guys in the world'. The transitive nature of the work means that it is difficult to form lasting relationships, and there is no room for sentimentality in the world they live in. This harsh reality is demonstrated by the death of Candy's dog, who is too old to be useful. Carlson, says 'He ain't no good to you... why n't you shoot him Candy?', demonstrating that the only reason the workers can comprehend for Candy keeping the dog is its usefulness. There is no provision made for the possibility that Candy's affection for the dog is enough reason to keep it.The dog also symbolises Candy himself. The dog has reached the end of its working life, and instead of being cared for in its old age, it is shot; because it is no longer of use to anyone, it is no longer worth keeping alive. Just before Candy's dog is shot, Slim remarks 'I wish't somebody'd shoot me if I got old and a cripple'. This reflects Candy's own situation; he has become useless in the context of the ranch to the extent that, in his position, Slim thinks that he would be better off dead. He is old and disabled, and no longer able to work effectively. However, he lives in a society where there is no provision for the care of the elderly, and so despite a lifetime of work, Candy is left to fend for himself without support. Candy is no longer of use, and so his life no longer carries any worth.