Yes, sand, 1” or more, some railroads specified 2-4”. The ATSF called for 2” of sand, and noted that “cinders are very undesirable.”
Instructions for livestock bedding is contained in the AAR Pamphlet #19 “Methods for Loading and Handling Live Stock”. The copy I have was Issued 1925, revised 1942. Similar (if the not the same) instructions can be found in many livestock handling brochures published by the railroads themselves. I have found copies on the net, so they are out there.
Hay or straw was to be used in cold weather. If for hogs, the straw must be one foot high around the sides and ends of the car to act as a wind break. 1 ½ bales per deck, in extreme weather 2 bales. Bales to approximate 200lb in weight.
During stormy or severe weather the sides of the cars were to be papered or battened to provide additional protection while allowing for ventilation.
Cars were to be clean, in Canada disinfected, before each use. Soiled bedding was to be removed