Bugzilla Bug 27727

A Cow is femail.
A Bull is mail.

Reproducible: Didn't try
Steps to Reproduce:
1. Go to www.gentoo.org.
2. Click on About in the navigation bar.
3. View the poster.

Actual Results:  
You see that Lary is a cow.

Expected Results:  
Lary should have been a bull.

-

Larry had udder implant surgery and gender enrichment surgery by a
world specialist in nonanthromorphic gender challenges.

Since his transformation, Larry prefers to be known as "Lary"
(pronounced "Lay-REE") and I am encouraged that you have shown him the
proper respect in this regard.

Larry was unsatisfied with his life as a mailman.  Wherever he went
people would say "there goes that four-legged mailman."  But because
he was tormented by his own gender identity, he always imagined that
they said, "there goes that four-legged male man."

This situation is what drove Larry to undergo several operations and
emerge as Lary.  Lary has since quit his job as a mailman and
spends his time hacking on the Linux kernel or commiting patches to
portage.

Welcome to the modern world. Cloning of animals, sex change etc. are daily
routines nowadays. Gentoo is a modern distribution :)

cow1 (kou)
n.

   1. The mature female of cattle of the genus Bos.
   2. The mature female of other large animals, such as whales, elephants, or moose.
   3. A domesticated bovine of either sex or any age.

See here ^^^^^^^^^
It's not false to call a male bovine cow.

http://dictionary.reference.com/search?q=cow

the english language is malleable, thus we can say whatever we want 

I also find :

[...]
       3: a large unpleasant woman

However, I think it's better to stick with Markus' interpretation :)

USE="male" emerge cow

This way you can get a male cow.