Which sentence uses a metaphor?

 - Our boots were muddy pig's hooves.
 - Our boots were as muddy as a pig's hooves.
This sentence uses a metaphor:
Our boots were muddy pig's hooves.
The words boots and pig's hooves are compared without the word like or as.
This sentence uses a simile:
Our boots were as muddy as a pig's hooves.
The words boots and pig's hooves are compared using the word as.