Jeff,
The Saxon Troops at Breitenfeld conisted of the following units of Horse:
Leibgarde
Taub'sches Regiment, 5 Companies 600 men
Hoffahne 'Companie Einspaenniger' 125 men
Leibgarde des Feldmarschalls, 2 Companies 200 men
Fuerstlich Altenburg'sches Regiment 1000 men
Bindauff'sches Regiment 1000 men
Steinau'sches Regiment, 3 Companies 600 men
1. Regiment Ritterpferde, Oberst Caesar Pflugt, 900 men
2. Regiment Ritterpferde, Oberst Gustachius Löser 800 men
Hope this shed some light on the term Ritterpferde(Lehnsreiter)
Günter