There is not a general term for newborn animals. Different animals are called different things. For example, newborn chickens are called chicks.
You call it a calf.
a chickity
a chickity
food
A pup
calf
kitten
A newbee
A calf
Shopping for a newborn can be tough. I think that the best gifts for a newborn are blankets, booties, or safe stuffed animals.
Any newborn bear, polar or otherwise, is called a cub.
Newborn