Help needed. Isn't this OWL document inconsistent?

Hi all,

I think the following OWL document is inconsistent,
but Pellet says that it's consistent.
Please shed some light on my ignorant brain.

@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>.
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>.
@prefix owl: <http://www.w3.org/2002/07/owl#>.
@prefix a: <http://www.ex.org/2005/ex#>.

a:Vegetarian
owl:intersectionOf
(a:Animal
[a owl:Restriction;
owl:onProperty a:eats;
owl:someValuesFrom a:Plant
]
).
a:Plant owl:complementOf a:Animal.
a:Sheep rdfs:subClassOf a:Vegetarian.
a:Cow rdfs:subClassOf a:Vegetarian.
a:MadCow
owl:intersectionOf
(a:Cow
[a owl:Restriction;
owl:onProperty a:eats;
owl:someValuesFrom a:Sheep
]
).

Thanks in advance!
Mekan Ikzain