What did George take from Lennie and throw in the bushes?

Lennie likes to touch soft things. This often gets him and George into a whole heap of trouble, as happened back in Weed. George and Lennie's dream of owning their own ranch involves Lennie tending the rabbits, where he'll be able to stroke their soft, fluffy fur to his heart's content.
Lennie also likes to stroke mice. Unfortunately for them, the big man doesn't know his own strength and sometimes ends up inadvertently killing them. In chapter 1, Lennie has one such unfortunate creature's dead body mouldering away in his pocket. George makes him give it to him and George throws it away. Not only is it rather unpleasant—not to say unhygienic—to have a dead mouse rotting away in your pocket, it also draws attention to the fact that Lennie has learning difficulties, and George figures that might jeopardize their chances of employment at the ranch.