Qitzur Shulchan Arukh – 189:4
The animal of a non-Jew, if the non-Jew is driving one of his animals, whether the burden is a Jews or whether it’s a non-Jews, he is not obligate [in the above two prohibitions]. He only has to remove the load, because of [the prohibition against causing] “pain to living things”, and he is permitted to accept pay for it. However, to load [the animal], he is not obligated at all — except if there is a possibility of enmity [by not helping].
But if there is no non-Jew there, rather a Jew who is driving the animal, he is also obligated to load [the animal] because of the pain of the Jew. Similar if it’s a Jew’s animal and a non-Jew’s burden [being carried by it], he must both unload and load [the animal] because of the pain of the Jew.