To make the sign for cow, make your hand into a fist then straighten your pinkie finger and straighten your thumb. The two extended fingers on your hand should like the horns of a cow. Take your thumb and put it by the side of your head and twist your hand around.
Use the cow sign with story books that have a bovine character. "Look, there is a brown cow."
Make a game out of all the animal flash cards. Start with a few very different animals with easy signs like cow, and add more animals as your baby progresses. As you present each animal flash card, introduce the animal,make the corresponding animal noise, and do the sign. “It’s a cow … mooooooooo …. mooooooooo.”