Livestock carriers can be divided into two categories – those designed to transport sheep, and those for larger animals such as cattle. The obvious design difference is the extra deck height required for the larger animals, but both require fodder storage, extensive water supply, excellent ventilation, suitable methods of animal waste disposal, non-slip decks, carefully designed ramps, and accommodation for those tending the animals. Most livestock carriers have been converted from existing vessels, notably sheep carriers from oil tankers, but occasionally specialised ships are constructed for the larger animals. These vessels are specifically designed and built to transport the many goods (meats, fruits, fish and vegetables, for example) which would rapidly deteriorate in ordinary hold conditions. Modern ‘reefers‘ are built with holds and decks providing good access for standard sized pallets and for fork-lift trucks, and are usually fitted with ‘side-ports’ – openings in hull sides permitting immediate access to cargo decks, the floors of which line up with quaysides. The layout of these vessels also makes them suitable for the carriage of motor-cars which fit beneath the restricted deck-heights, as well as for other non-refrigerated and palletised cargo, although many of these vessels trade exclusively in the refrigerated markets on long-term contract employment. Certain reefer trades are losing out to the containership market with the advent of refrigerated containers, but there remains a substantial and lucrative reefer market for those with specialist knowledge and vessels.