I quote;
"One common practice that many well intentioned rabbit owners do is putting their pet rabbit in the same pen that houses their chickens or goats. Some will even let the rabbits live on the ground loose without an elevated area inside the pen that the rabbit can retreat to.
It simply is not an ideal situation to house rabbits together with other outdoor animals such as chickens or goats, and here is why:
The most common intestinal microscopic parasite of rabbits, goats and birds (especially chickens, ducks and geese) is Coccidia. These parasites found in the animals’ stool multiply invisibly on the floor close to the ground, especially in chicken floor spaces.
Chickens carry lots of Coccidia. Rabbits, especially young rabbits, who get infected with Coccidia can develop growth retardation and stop eating. They can also experience diarrhea, constipation, liver failure and eventual death.
Goats who are housed next to chickens are even more susceptible to developing Coccidia induced diarrhea. They can stop eating, become dehydrated and eventually die. Very young goats (those who are less than four months old) are especially susceptible.
Outdoor rabbits need clean living areas that are kept free from manure of any sort daily. They need hutches with good ventilation so they don’t get stressed and be at increased risk for serious Pasteurella respiratory infections.
Chickens defecate constantly. They are messy and create dusty areas due to the way they eat. So again, chickens should not be sharing the same floor space with pet rabbits. Furthermore, rabbits who eat chicken food are at risk to develop an intestinal blockage, and this is cause for an emergency situation to an unsuspecting pet owner"
There is also of course the issue that chickens could possibly attack and eat any baby bunnies.....