Don't think that just because you have 'Farm Cats' that these animals are anything like healthy or happy.
The problem is not simply that you have a kitten under the hood. The problem is that you have an unmanaged colony of Feral cats.
Most of those cute little kittens are going to die from disease, exposure, or be chewed up by coyotes.
The kittens that survive the first few months will be lucky to live for two years.
Feline leukemia outbreaks can wipe out the entire colony ( http://www.vet.cornell.edu/fhc/brochures/felv.html ). Death by FeLV is a miserable death.
At the very least you must trap these cats, have them spayed/neutered, and tested for FeLV.