What is a metaphor in the first paragraph of Atwood's "All Bread"?

One metaphor found in the first stanza of Margaret Atwood's poem "All Bread" is the following, which opens the poem:

All bread is made of wood, Cow dung, packed brown moss, The bodies of dead animals, the teeth And backbones, what is left After the ravens.

The poem in its entirety describes the process of making bread in four stanzas. The first describes the wheat growing in the dirt; the second focuses on the process...

One metaphor found in the first stanza of Margaret Atwood's poem "All Bread" is the following, which opens the poem:

All bread is made of wood,
Cow dung, packed brown moss,
The bodies of dead animals, the teeth
And backbones, what is left
After the ravens.

The poem in its entirety describes the process of making bread in four stanzas. The first describes the wheat growing in the dirt; the second focuses on the process of baking bread; the third imagines someone eating the bread after a long day of physical labor. The poem concludes by claiming that eating bread is eating the earth, and bread is meant to be shared. Overall, the bread could be interpreted as a metaphor for love and family because it is described as mundane and ritualized, yet it is crucially important that it is shared. By this interpretation, the dirt in the first paragraph could be a metaphor for how love is created and sustained by the earth, like the various substances in the dirt like cow dung, moss, and rotting animal remains all work to grow wheat.