According to Booth's Listing, the only Butler that was in a Cav unit is:

Butler, D. S., Pvt. Co. E. 13th Battn. La. (Partisan Rangers). En. Aug. 15th, 1862, Monroe. La. Roll for Nov. and Dec., 1862, Present. Roll for Jan. 1st to April 30th, 1863, Absent. Detached service.

The only 'Regiment' with Capers as a commander was the 5th La. It was formed in Feb. 20, 1864, long after Butler was appearently sent on detached service. Please note, the 13th appears to have been the main group that formed the 5th Regiment in 1864.

Hope this helps (and is not toooo confusing)

JIMT