Zero plural question?

can someone give me links that tell me about zero plural. it was explain in a grammar book, only part of it is understand. here is a copy of the text. In some cases nouns have zero plural; in other words, they remain unchanged in the plural. These are, most notably, nouns referring to animals, maybe because... show more can someone give me links that tell me about zero plural. it was explain in a grammar book, only part of it is understand.

here is a copy of the text.

In some cases nouns have zero plural; in other words, they remain unchanged in the plural. These are, most notably, nouns referring to animals, maybe because we often see animals in both number and mass. We may eat/keep as a pet/be attacked by an individual animal, but we also make our living by breeding cattle or order salmon for a meal. Other cases include sheep, deer, cod, grouse and trout.

thanks for the help.
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