Ottoman cavalry was poor in quality and rarely used. Good cavalry is expensive and labor intensive to maintain in a good condition and the Ottomans at that time did not have the discipline for a good cavalry force.
I think we have to be very careful about what has been written and what is more and more coming out. Thanks to great translation works, recent books have discovered that the Turkish army was far from being as disorganised as people were generally saying. I read part of the "4 years in Turkey" by Liman van Sanders, which for a long time was the only true reference to the Ottoman army. Liman was at odds with most officers for the simple reason that they would not comply to all his orders... that gave a distorded image to the world about the state of the Ottoman army. The Ottoman cavalry in particular had much better horses than their European enemies for the simple reason that they used shorter, sturdier animals, which could resist the harsh desert and mountain environments. As far as quality is concerned, this cavalry cannot be compared to any of the Western powers, but it certainly was the best in the region, in which I include Greece, Bulgaria etc.