A boar or a sow, depending on the gender.
sow
A pigletWhen a new pig baby is born it is called a piglet.
A Piglet.
Piglet
piglet
piglet
A piglet.
A Piglet.
A small, baby pig is usually called a piglet in North America.
A young warthog is called a piglet.
It's a baby, It's cute, much smaller, much slimmer, and more energetic.
A baby guinea pig is called a kit; A baby pig is called a piglet.