Itchy horses
 

So they scratched. Or had something else done to them.

R 4) #4 had his argumentive self calmed down...is a gelding now.
#6 was itchy, and scratched.
#8 must have caught it from the 4, he's a new gelding, too.

R 5) #1is no longer coupled, because 1A scratched. Must be catching.
#4 has crabs, it scratched.
#5 is now better behaved, now a gelding.
#7 is behaving better, too. Now a gelding.
#13 also eligible into the itches, scratched.

R 6) #1 + 1A broke up, 1A scratched.
#7 is itchy. Scratched.
#8 is too, been hanging with the #11, too, must be contagious.
R 8) #1 and 1A are divorced, #1A scratched.
#3, #8, #15, #16, and #17 all scratched. Must have been an awesome party.
R 10) #5 was there, too, scratched.
R 11) #2 had a party, too, scratched
#3, scratched.
#6, scratched.
And a good time was had by all. :D