HORSE:
“Horsing around” – means to be fooling around, wrestling or playing physical games.  Little kids are often told to stop this by parents. E.g. “You boys stop horsing around outside and come eat your dinner!”
“I’m so hungry I could eat a horse” – means to be so hungry that you can eat a lot of food.
“You can lead a horse to water, but you can’t make him drink” – means that you can guide someone to the answer or to a good solution to their problem/situation, but you cannot force them to do the thing that you recommend.  E.g. John:  “Did Jimmy quit smoking yet?”   Barb:  “No.  I showed him pictures of cancer victims and everything, but you know what they say, you can lead  a horse to water…”
“Work like a horse” – means to work hard.

DOG:
“Dog-tired” – means to be very tired, just like a panting dog.
“Dogging me”: – to ‘dog’ is to pursue.  Just like a hound dog chasing a deer, we can say that a person or issue is dogging us or hounding us.  E.g. “The boss keeps dogging/hounding me about that report that’s due at 5pm, so please help me out and give me your notes!”
“Sick as a dog” – means to be very ill.  We get a wet nose, just like a dog!
“Lazy as a dog” – means to be lazy.
“Work like a dog” – means to work hard, like a sheep dog.

CHICKEN & ROOSTER:
“You’re (a) chicken” – means to be afraid or to be a coward.  E.g. “You won’t go into that old haunted house because you’re (a) chicken!”  Notice that you can use this word as a noun or adjective.
“Cocky” – from the British English name ‘cock’ or what the North Americans call a rooster.  The attitude displayed by the male chicken on a farm is ‘cocky’ because he walks around as if he owns the place!  Calling someone cocky usually means that they are over-confident or arrogant.

PIG:
“Pig out” – means to eat like a pig, and consume a lot of food in a short amount of time.
“Pig-tails” – the cute hairstyle that girls wear when their hair is separated into two ‘pony-tails’ on each side of their head, thus looking like two bouncy curled-up pig-tails.
“Pig-headed” – means to be stubborn.  We can also say ‘bull-headed’ to mean the same thing.

These idioms are up-to-date and ready to use in everyday life, or in the office.  They are the same idioms I teach my clients and students.  Enjoy!