The same thing it is on cows. They have 2 "nipples" that produce milk when the horse is pregnant or has a baby. The baby drinks the milk from the mama's utter.
Yes zebras do have belly buttons so do horses, dogs, and donkeys the belly button is right in front of the udder
The teats on the udder.
Foals generally nurse from their mother's udder to consume milk. An orphaned foal can be bottle fed milk replacer.
An udder is a bag-like organ situated between the back legs that contains mammary tissue which are used to generate and synthesize milk. All female ungulate animals (from horses to deer) have udders: this sex organ is not specifically restricted to cows and cattle.
The Udder.
The floor of the udder is just that- The floor of the udder. The shape of the udder is determined by the medial and lateral suspensatory ligaments. Poor ligaments mean a saggy, mastitis prone, misshapen udder.
The mare's teats and udder will look slightly different after foaling. The teats will be slightly longer than they were before.
After the tenth month of pregnancy - the udder will begin to spring, the teats becoming clearly defined. As foaling approaches it will appear quite large and swollen, globules of wax appear at this stage, the mare should be watched closely, as foaling generally occurs within 24 hours. When globules drop off and milk appears, and when the muscles of the quarters sag on either side of the croup, her time is nigh. The vulva will soon distend, indicating that she will shortly come into labour
A complex system of ligaments holds the udder to the abdomen.
When the cow's udder is full and heavy, it needs to be milked.
Cows only have one "breast," and that is the udder.
The udder will only swell, the cow is dropping her milk into the milk cisterns in the udder for the calf to suckle.