A non-Jew who is just hired to a Jew, even for a long time, can do work on Shabbos.

Chapter 305 Section 1

We learn from a posuk that even your own animal cannot do work on Shabbos, which includes carrying. Chazal explain having the animal wear something so that the animal could be monitored is not considered carrying but if it is for beauty or for purposes more then simple monitoring, it is considered carrying.

Chapter 305 Section 2

A rope in the mouth of a horse is not permitted.