To get a raw deal or the short end of the stick. Derived from the behavior of barnyard pigs. The "runt" or weakest piglet is forced to nurse on the tit farthest back on the mother pig, which gives the least nourishment.
Not getting a fair share. Many female mammals have multiple rows of breasts, for example dogs. Typically the rear most pair of breasts is smaller and less developed than the rest. Hence a pup nursing from the rear most breast is likely to receive less milk than other nursing pups. Hind means rear most. Tit is slang for breast.