The mother looks after and provides milk for her offspring.
A swine offspring is called a piglet.
Offspring of ducks are called "ducklings" and that of geese are called "goslings."
Pigs offspring are called piglets.
A Mares' offspring is called a "Foal".
A male seal is called a bull
....an old elephant seal! I don't think there's any special name for elderly seals or sealions. Males and females are called bulls and cows, and their offspring are known as calves or pups, but I don't believe they aquire any special title due to their advancing age.
The offspring of a lion is called a cub.
A whales offspring, is called a calf.
A jaguar's offspring is called a cub.
A buffalo offspring is a calf.
The visible trait an offspring exhibits is called the phenotype.