Learn German: Wir sehen keine jungen Schafe. - We don't see any young sheep.

In this sentence, jungen comes after the negative plural article keine. Whenever you have a plural noun following a definite article (like die), a possessive (like meine), or a negative article (like keine), the adjective before the noun always gets an -en ending.

Is Schafe singular or plural? In English, 'sheep' can be both!

It is plural here. In German, the singular is das Schaf (the sheep) and the plural adds an -e to become die Schafe. You can also tell it is plural because of the plural article keine.

What case is keine jungen Schafe in?

It is in the accusative case because the sheep are the direct object—they are the things being seen. For plural nouns, the accusative endings for articles and adjectives are exactly the same as they are in the nominative case.

Why do we use keine instead of nicht to say we 'don't' see them?

When you negate a noun that doesn't have a definite article, German uses a form of kein. Instead of saying 'We do not see young sheep' with nicht, German phrases it literally as 'We see no young sheep'.