On 7 February 1863, the regiment had 21 servicable and 17 unservicable horses (this should probably be 17 mules) [consolidated morning report]. On 11 February 1863, the regiment had 21 servicable horses and 17 mules (consolidated morning report).
While the regiment was in the 1st Brigade, 3rd Division, no mules were available. The Assistant Quarter Master therefore issued them two pack horses to carry Officers' Shelter Tents. These were "turned over", probably in June 1863, since Sinex then complained that he had nothing to carry the Shelter Tents. [letter, Sinex to Marvin, 22 June 1863]
Several months later, on 5 September 1863, Sinex ordered Henry Larnay, co I, to return to his company, because the "pack mules [had] been turned in by order from Brigade Head Quarters" (special order 73, HQ 91st PA, 5 Sep 63). Perhaps this is related to the general order from HQ Army of the Potomac, dated 21 August 1863, which the 91st received on 24 August 1863, "relative to the amount of transportation allowed", or to the general order they received on 3 September 1863, dated 7 August 1863, from the Adjutant General's Office in Washington DC, about the amount of transportation allowed in the field. It is probably related to the order they received from brigade headquarters on 8 September 1863, about the transfer of pack mules and the return of the men in charge to their companies.
On 16 April 1864, Sinex ordered all excess officers' baggage to be sent to the rear; officers were permitted only 2 blankets, a small valise, and a reasonable-sized mess kit (circular, HQ 91st PA, 16 April 1864).