Veterinary Handbook Disease Finder

Veterinary Handbook Contents

7.3 Deck Washing

Ideally, deck washing should be planned so that cattle decks are washed before the manure builds to a depth that impacts on the comfort of the livestock and before the deterioration of the pad due to excess moisture content. The decision to wash should be made based on the worst affected pen areas, and with enough planning to give the crew adequate preparation time. 

Washing is required when the depth or consistency of the manure pad is starting to - or is likely to start - affecting the comfort of the livestock. A deep, tacky manure pad hinders the mobility of the livestock and the build-up of manure can make some areas of the pen less accessible thereby inhibiting the free movement of stock around all areas of the pen, consequently increasing stocking density in the rest of the pen. Livestock may be reluctant to sit or lie down if the depth of the pad is excessive or if the pad has a high moisture content and has deteriorated to become boggy or sloppy. Ammonia from the manure pad can create issues with air quality and can significantly impact the health and well-being of the livestock and possibly the crew. 

High ambient temperatures on deck will cause an increase in the amount of water consumed by the livestock and when water consumption increases, urine output will also increase. The manure pad will deteriorate when animals are producing more liquid waste than the bedding can absorb and the ventilation system can evaporate.

The evaporation of moisture from the manure pad will further contribute to the humidity and wet bulb temperature on decks. Coat contamination occurs when the pad moisture is high and particularly affects medium to heavy-coated animals. Marked coat contamination will impact the animal’s ability to dissipate body heat. 

Managing the manure pad on board export vessels is an integral part of reducing the risk of heat stress - less heat tolerant animals will require washing sooner or more frequently than others. It is essential to plan ahead and wash deck areas before the hottest parts of the voyage as it can be detrimental to wash down decks if the livestock are heat stressed. 

The washing schedule must work alongside the ship’s systems and requires proper planning and clear communications between the stockpersons, veterinarian and crew (Captain, Chief Officer and Bosun). The crew will need time to prepare the labour force and equipment required for the wash, the drainage and bilge pumps need to be prepared to clear the wastewater from the decks, and distribution of sawdust and shavings to pens areas will follow the wash. The ship’s trim and list will affect water runoff and can usually be adjusted to achieve optimal drainage. 

Washing cannot take place in bad weather conditions or rough seas and the ship must be able to discharge the organic waste overboard in accordance with the International Convention for the Prevention of Pollution from Ships (MARPOL regulations). Planning to wash the ship early is safer than delaying the wash and running the risk of unforeseen events arising that will further delay the ability to conduct a wash. It may not be possible to wash the whole ship in one day - the amount of manure build-up, the size of the labour force, water pressure and drainage will determine how much deck space can be washed each day. Areas of the ship may need to be washed preferentially and over a series of days. After the initial wash, there will inevitably be some water remaining on decks and the time frame before a subsequent wash is required will be shorter than the period between loading and the first wash. Plan a conservative deck washing regimen for the whole voyage and be prepared to adjust the timetable based on deck conditions, weather predictions and the voyage progression. 

Discuss a plan for re-applying bedding to pen areas following the wash when planning the washing schedule. The amount of bedding to be spread will depend on the type to be used, the quantity available, the quantity remaining on board, the amount of water remaining on decks after the wash, and the ability to distribute and spread the bedding in pen areas. Spreading bedding after the wash is labour intensive but it will reduce humidity and improve air quality as well as footing and traction, encourage stock to rest and reduce coat contamination.