The vet tells the farmer that he should try artificial insemination.

The farmer doesn't have the slightest idea what this means but, not
wanting to display his ignorance, only asks the vet how he will know
when the pigs are pregnant.

The vet tells him that they will stop standing around and will,
instead, lay down and wallow in the mud when they are pregnant.

The farmer hangs up and gives it some thought. He comes to the
conclusion that artificial insemination means he has to impregnate
the pigs. So, he loads the pigs into his truck, drives them out into
the woods, has sex with them all, brings them back and goes to bed.

Next morning, he wakes and looks out at the pigs. Seeing that they
are all still standing around, he concludes that the first try didn't
take effect, and loads them into the truck again. He drives them out
to the woods, bangs each pig twice for good measure, brings them back
and goes to bed.

Next morning, he wakes to find the pigs still just standing around.
"One more try," he tells himself, and proceeds to load them up and
drive them out to the woods. He spends all day shagging the pigs and,
upon returning home, falls listlessly into bed.

The next morning, he cannot even raise himself from the bed to look
at the pigs. He asks his wife to look out and tell him if the pigs
are laying in the mud.

"No," she says, "they are all in the truck and one of them is honking
the horn."