Question

what is the advantage of being an omnivorous animal such as a pig

Answer 1

they can get dirty and no one complains to keep themselves cool

Answer 2

Omnivorous means you eat plants and animals/ meats. Advantages of this include the ability to eat basically anything to get the required nutrients, instead of leaving out proteins like herbivores do, or vegetables like carnivores do.
Basically, you can eat whatever you want to get what you need.

Hope this helps!