Dromedaries, or mules, by comparing this with 2 Chronicles 9:24; or post horses, which are particularly mentioned and distinguished from the other horses, because they took a more exact and particular care about them. Howsoever, it is agreed that these were swift beasts, which is evident from Esther 8:10,14 Mic 1:13.
Related Commentaries of 1 Kings 4:28
1 Kings 4:28
28 Barley also and straw for the horses and dromedariesg brought they unto the place where the officers were, every man according to his charge.