This is the 531st most frequent Swedish word.
djur
"Animal."
Here, 'djur' is used as a singular, indefinite noun referring to an animal in general.
Jag såg ett djur i skogen.
I saw an animal in the forest.
Here, 'djuren' is the plural, definite form of 'djur', referring specifically to the animals on the farm.
Djuren på bondgården är glada.
The animals on the farm are happy.
In this question, 'djur' is used in the singular, indefinite form, as part of a question asking for a preference among animals.