spring chicken

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A young chicken, especially one from two to ten months old, having tender meat.
• noun Slang A young person.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A chicken for eating while it is still young.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a young person (especially a young man or boy)
• noun a young chicken having tender meat