It really depends on how you define things but I'll also provide my little grain of sand.
Basically it's part of human sexuality. Pretty much all aspects of the sexual life of an individual are deeply rooted in how your brain is formed, shaped, constructed. Your inner connections and the ways they interact with each other. It's part of our nature as living orgamisms. Behaviour runs in the blood, it's conditioned by our genetics. Sure, our ambient while we develop may influence us one way or another but it can't overwrite what we're made of.
The main difference is what you decide to do about it because that entirely revolves on who you are as a person,. Your beliefs, your values, your experiences, your preferences, your opportunities, your errors, your skills, your advantages, etcetera. You may not be in control of your liking of animals sexually, either if that also has an emotional component or not, but you do have entire control on what you do with it. Whether you never do anything, or looking for an animal partner, the way you care for them, they way you connect with them, and the way you explore your sexual interests with them.