D.C. Code § 22-1003
No railroad company, in the carrying or transportation of animals, shall permit the same to be confined in cars for a longer period than 24 hours, without unloading the same, for rest, water, and feeding, for a period of at least 5 consecutive hours, unless prevented from so unloading by storm or other accidental causes. In estimating such confinement the time during which such animals have been confined without such rest on connecting roads from which they are received shall be included; it being the intent of this section to prohibit their continuous confinement beyond the period of 24 hours, except upon contingencies hereinbefore stated. Animals so unloaded shall be properly fed, watered, and sheltered during such rest by the owner or person having the custody thereof, or in case of his default in so doing, then by the railroad company transporting the same, at the expense of said owner or persons in custody thereof. And said company shall, in such case, have a lien upon such animals for food, care, and custody furnished, and shall not be liable for any detention of such animals authorized by this section. Any company, owner, or custodian of such animals who fails to comply with the provisions of this section shall, for each and every such offense, be liable for and forfeit and pay a penalty of not less than $1 nor more than $500; provided, however, that when animals shall be carried in cars in which they can and do have proper food, water, space, and opportunity for rest, the foregoing provisions in regard to their being unloaded shall not apply.
D.C. Code § 22-1003