Lyric discussion by washcfl 

The "Mares will niegh/with stallions that they mate" refers to a line earlier in the play where one of the characters talks about how mares and stallions aren't ashamed of their sexuality.

I thought the mare will neigh with stallions that they mate, foals theyve born, refers to Melchior, Wendela, and their unborn child. How they will always be together, whether dead or alive.

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