A farmer and his wife

A farmer and his wife were lying
in bed one evening; she was
knitting, and he was reading the
latest issue of Animal Husbandry.
He looked up from the page and
said to her, "Did you know that
humans are the only species in
which the female achieves
orgasm?" She looked at him
wistfully, smiled, and replied, "Oh,
yeah? Prove it." He frowned for a
moment, then said, "Okay." He
got up and walked out, leaving his
wife with a confused look on her
face. About a half hour later, he
returned all tired and sweaty and
proclaimed, "Well, I'm sure the
cow and sheep didn't, but the
way that pig is always squealing,
how can I tell?" more