EA France has listed some info from GamesCom thanks to SimGuru Graham.

Step 1: Create a pet!

In this expansion pack, the animals are really full of Sims. You will be able to create cats, dogs, and for the first time in a game Sims … horses! “We know that this animal was highly anticipated by our players! We are very pleased to be able to integrate this new expansion pack, “says Graham. As for your Sims, the creative possibilities are endless and each animal can be truly unique. So you can choose from a list of predefined breeds (Labrador, Chihuahua, …) or create a right out of your imagination. And for this tool fur texture inspired to “create a pattern” and “create a tattoo” will be a great help!
As for your beloved Sims, you will also define the personality of your pet. You must choose three traits among more than twenty (brave, clumsy, playful, friendly, lazy, …).

Step 2: Discover a new city!
Your Sims will evolve into a whole new town of Appaloosa plain sweet name (in the English version of the game). For the record, Appaloosa is the name of a breed of horses available in the game that has particularly attracted the studio

Discover new places specially dedicated to the animals! As your Sims’ pets can improve their skills and one of the most effective ways is to take them to these new places reserved for them. Make work your cats agility by making them climb strange structures, let your dogs swim in pools in the shape of bones or take your horse galloping through an obstacle course that ends with fireworks!
My favorite place in your heart? The ranch horse (I’ve always liked cowboys  !) If you do enough work on your horse’s skills increase and you will be able to compete, win prizes and money by going to this place. If you can not take your Sims on the inside of this place you can still change some settings to ensure that your trusty steed won the competition! You will be surprised!

Step 3: Set up a cozy little corner …
“Players will find many items for their animals can live in their homes: a basket for cat, a dog kennel, litter. There will be more fun things! My three favorites: the hedge pyrotechnic obstacle course for your horses, the ball for the dogs and the laser pointer to entertain your cats! “Graham told us.
And since a horse is a little more bulky than a dog or cat, you can adjust it a barn with hay, a box … This is also one of the new mode of construction!

Source: SimsVIP