The story revolves around a failing dairy farm run by Dan Reilly (John Lynch), who's allowed a government firm to conduct genetic experiments on his cattle. Meanwhile, a couple of young Traveller runaways, Jamie (Sean Harris) and Mary (Ruth Negga), are found hiding away on the farm, and Dan insists they leave by morning.
That night, however, one of Dan's cows gives birth to a calf, with Jamie's aid. A calf with fangs. Upon terminating and dissecting the malformed newborn, they soon discover that the calf was itself pregnant, with even more mutated chest bursters...
This film provides examples of the following tropes:
- Attack of the Killer Whatever: Attack of the killer mutant parasitic dairy cow!
- Body Horror: The mutant cow is barely even recognizable as a cow at all, save for its head resembling a deformed calf skull. Most of its body is a jumbled exoskeletal mess and it appears to walk on its external ribs like some kind of bovine centipede.
- Chest Burster: How the mutant cow spawn reproduces, by infecting other cattle and producing parasitic larval offspring that burst out of the cows.
- Explosive Breeder: The creature is an unwanted by-product of an experiment to produce more fertile cattle: one that worked a little to well as the calves themselves were born already pregnant with the mutant cow spawn.
- Face Full of Alien Wing-Wong: The parasite creatures can also reproduce through infecting human cells, which cause more creatures to grow within the infectees.
- Mama Bear: The mother cow is visibly distressed when Dan decides to euthanize her malformed calf, forcing Orla, the veterinarian, to euthanize her as well for their safety.
- Nothing Is Scarier: The cow spawn is never shown in full, and with its confusing anatomy, it's difficult to discern what it even looks like save for some behind-the-scenes photos of the adult cow spawn puppet.
- Skeletons in the Coat Closet: The mutant cow spawn have their skeletons growing on the outside of their bodies.
- Super Not-Drowning Skills: The cow spawn are inexplicably amphibious.
- Well-Intentioned Extremist: After the parasitic nature of the cow spawn became evident, the Doctor tried to kill everyone else with a nail gun to prevent the creature from spreading beyond the farm.
- Xenomorph Xerox: With chest-bursting parasitic offspring, a tendency to hide in narrow spaces, and an exoskeletal appearance, the cow spawn certainly fit the bill.