It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) gave nothing to the kawdan (a slow-paced pack horse), and gave it less than the share of the 'uzzab (unmarried riders) in strength and quality. And kawdan means a slow-paced pack horse.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12663