Baby chicken registering hitbox larger than 1/2 block

My minecraft beta updated today, and since the update my chicken farm has stopped working. It takes advantage of the hitbox of a baby chicken being only half a block. They are dispensed onto a slab with a full block above them. before the update they suffocated only when adults, but after the update it at least appears that the hitbox of the baby chicken is registering the same as an adult chicken (1 full block).