Which is the correct sentence?
- The young cow is calf.
- The young cow is called calf.
- The young cow called as calf.
None of your sentences are exactly correct. If you want to make statement about what a young cow is called, try:
A young cow is called a calf
None of these work.
The most natural one is:
A young/baby cow is (called) a calf.
If you wanna use "The" at the beginning of the sentence, then it would be:
The baby of a cow is (called) a calf.