Horses

For the sake of making the story easier to write and to avoid overcomplicating and overshadowing the plot, working animals will be very similar if not the same as in real life. 

Horses are used primarily used for transportation whether that be on horseback or a horsedrawn carriage. For the information network, horses are bred for speed and stamina to allow messengers to travel the Kingdom as quickly as possible. These horses are extremely expensive even after they are retired from service. Due to the expense and prestige, nobles seek to buy retired horses and breed them to earn a profit.
For merchants, they seek horses that a strong and have little need for ones that are fast. Horses used to pull supplies are not specially bred but are still sought after. Due to this fact, these horses while not expensive, are still difficult to buy and cost a median price.
Horses that an improperly bred are do not have the traits highly sought after are the easiest to purchase and are used by farmers for simple city travel and fieldwork. 
During this time, the kingdom is attempting to make paved roads from the six major cities to allow easier travel as carriages have become more popular and easier to acquire for the higher class. Due to this fact, although nobles seek out horses bred for speed, they are slowly shifting their focus to stronger horses which have started to create tension in the market for merchants as the horses they need for their job are taken from them. 
In the city of Atemdo, horses are cherished. They have a law that no horse is allowed to be worked for more than 10 years and if they are messenger horses that time is shortened to 8 years. Once the horse is retired, they are used to teach young children how to ride but are mainly kept and pampered for the hard work they did for the people of Atemdo. All horses that are retired bred and are bought for a small sum to help people buy a new horse. If the horse is young and highly sought after, the city will trade the old horse for a new one.