Beast of burden is a term commonly used to describe animals that are domesticated and trained to carry heavy loads or work on farms. However, there are several other terms that can be used interchangeably for such animals. One of the synonyms is "pack animal" which refers to an animal that can be loaded with goods and carry them on their back. Another synonym is "draught animal" which refers to an animal that pulls a plow or a cart. "Workhorse" is also a commonly used synonym for a strong and sturdy animal that can be used for manual labor. Other synonyms include "oxen", "donkey", "mule", and "camel".