You can't get custom spawners with /give.
Using this command:
/setblock ~ ~ ~ mob_spawner 0 replace {SpawnData:{id:Cow}}
it will make a cow spawner as expected. When using the command:
/give @p mob_spawner 1 0 {SpawnData:{id:Cow}}
it will be a default pig spawner and there is no way to get a cow spawner. In 1.8 and some of the snapshots, you could get custom spawners using the EntityId tag, but that was removed.

(It also makes a normal pig spawner when using the SpawnPotentials tag)