Understanding Livestock Carriers

Livestock carriers are cargo vessels used to transport cattle, sheep, goats, cows, buffaloes, etc. They are crucial links in the world's food supply chain where several nations profit from exporting cattle at higher rates, and many countries access good quality meat and other extractives from the livestock.

Other than international livestock transport, livestock carriers are also used for shipping cattle from one state to another within the country. Most livestock carriers ply from Europe and Australia to Gulf countries.

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One important thing to consider while designing livestock carriers is that livestock or animals are to be transported as cargo only. So, perhaps that makes them the only type of cargo actually ‘living.’ Humans carried on passenger vessels and ferries are treated as proper passengers, not cargo!

However, a crucial aspect here is that, unlike any other cargo, ensuring that all animals remain alive and healthy throughout the journey is vital and indispensable.

Any loss or incapacitation of livestock translates to a loss in business. So, other than accommodating the given capacity of animals, the vessel must be congenial to sustain such a large number of animals and cater to their upkeep.

While IMO and SOLAS regulations still need a clear-cut framework for the design and construction of livestock carriers, they have some provisions that can be applied to livestock carriers and are loosely based on the general guidelines for passenger and cargo vessels.

However, individual nations that have livestock carriers classed under their names have worked on more detailed frameworks for their design and arrangement, such as the comprehensive regulations covered under MO43 of Australia or the DGS Order 4 formulated by DG Shipping, India.

Many livestock carriers are converted from older cargo vessels such as containerships or are built indigenously for that purpose. The crux of design for livestock carriers is based on the following requirements:

Now, let us discuss them briefly.

First and foremost, the loading and unloading of the livestock onboard is a crucial aspect. Unlike other cargo vessels, they can't be directly hauled using mechanisms and, thus, must be appropriately guided by competent personnel into their respective holds in mass numbers. Care is taken that the animals are not injured. Conversely, excess ingress of the cattle does not damage the ship's internal structural components or interfere with any equipment or systems onboard.

Also, like loading and unloading other cargo vessels, care is taken such that the weight distribution remains compliant with the stability requirements and does not alter dramatically, affecting the vessel's stability. Thus, livestock is uniformly arranged during stowage and penning, so there is no significant differential loading at any point on the vessel.

Now that the livestock gets loaded, the next concern is the accommodation of the cattle within the designated spaces. Most livestock is stowed in pens-like enclosures within the main cargo space. These pens are arranged in rows and are separated by passages or alleyways. These, in turn, are placed in multiple decks, often connected by internal and external sloping ramps.

Based on the type of livestock, the pens are designed such that the designated number of animals can be stowed in the given floor area without cramming or crowding. Extra space is allocated for livestock types of heavier build, like buffaloes or horned animals like bulls, and furry ones, like heavily wooled sheep. Though the exact floor area designation depends on the guidelines, a 10% extra margin is usually given for all practical purposes. After estimating the livestock size and required spaces, the pens are designed.

Now, these pens must cater to the given size of livestock and have adequate clearances for proper aeration and ventilation. Moreover, it must be such that there is no crushing amongst them, and they have access to the feeding spaces and water supply. Though the spaces designated vary based on guidelines and the type of vessel and livestock, higher space is allocated for heavier cattle as a general rule.

However, the maximum individual pen size for livestock in a carrier is 40 square metres. Also, the precise height of pens is kept around a minimum of 1 metre. Sometimes the height may also be in the order of 2 metres.

The pens are often hemmed by suitable longitudinal guard rails on the sides. The maximum distance between these rails is kept low to avoid the escape of the animals through them and is usually around 200-300 mm. Also, the distance between the lowermost rail and the floor is kept low, within a maximum of 200 mm.

As the pens are arranged in rows, they are separated by passageways. The passageways separating two rows of pens on either side are usually characteristic of widths around 900-1000 mm, and those having pens on only one side have widths of around 750-800 mm. These minimal space requirements are to avoid injury from animals to crew and cramming and overcrowding during loading and unloading operations.

Connected ramps separate all spaces for cattle and livestock at different vertical deck levels. Once again, the specifications of the ramps may vary from vessel to vessel, but the minimum width is usually around 500-600 millimetres. Furthermore, they extend to a maximum height of 1 metre above a level and have a gradient ratio or slope aspect of about 0.5 or 1:2. They are often characterised by floor battens.

The main cornerstone for strength design in livestock carriers is that livestock is a live or dynamic load rather than a static load. This means that they essentially induce a time-varying dynamic component, which means a greater degree of oncoming loads.

So, everything from the boundary walls and rails of the enclosures or pens to the strength of the deck surfaces should be scrupulously considered in the design. Speaking of decks, the initial strength is usually based on the size of the vessel and the livestock it is deemed to carry. Moreover, it also depends on the cattle type. However, the design of the floor deck is such that it should be capable of supporting a load 1.5 times that expected per square metre derived initially from the cattle size and type.

After decks, the guard and pen rails should withstand a higher degree of loads from the impact forces of animals. They are variable based on guidelines. Railings’ connections, bolts, and hinges are also designed to withstand heavy loads. The decks are stiffened.

Apart from the clear heights above the stowage spaces, a proper ventilation system should also be provided to allow air ingress and a proper passage of accumulated vapours. This is of utmost importance for the survival of the livestock for long stretches of the journey.

Mechanical ventilation systems are commonly used for forced air circulation and exhaustion and are designated based on guidelines as per livestock size. Moreover, the decks for stowage of the livestock also have suitable clear openings and recesses for cross-ventilation and proper oxygenation. However, no means of aeration and ventilation is required for livestock stowed at open or exposed weather decks.

After aeration and ventilation, a regular supply of food and water is also essential. A livestock vessel should have sufficient space to carry surplus feed for the animals throughout its voyage. As a rule, the feedstock is kept at an excess margin of over 25%. The stowage spaces of feed are completely different from that of the livestock. For larger vessels carrying a big livestock size, water supply is usually through pipes carrying fresh water from the freshwater tanks to the livestock spaces. Purification and filtration systems are present onboard and are powered by auxiliary systems as a part of the hotel load.

Regarding power, the consumption is relatively high for livestock carriers as they are required to cater for all sorts of utilities from lighting, ventilation and aeration of the pens, pumping water and drainage systems, and so on. All vessels have primary and secondary sources of power.

All pens are equipped with suitable drainage systems to remove animal wastes. As per MARPOL requirements, wastes from the animals are either incinerated or stored in sewage tanks without directly releasing them at sea.

Structural fire protection is as per the requirements of SOLAS 74.

Like strength, stability is also essential for livestock carriers as there can be effects due to the shifting of livestock. Different flags have their guidelines for stability and empirical formulations for stability design.

The heeling lever and all information pertinent to the statical stability curve are typical for the given design. Thus, the plan is done so that due to an abrupt shift of livestock, if the vessel lists to one end rapidly, the righting lever must be large enough to create an equivalently large restoring moment to bring the vessel back upright. Also, the vessel must neither be too stiff nor too tender.

The other stability requirements, as per weather and external heeling moments, must also be met.

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Subhodeep is a Naval Architecture and Ocean Engineering graduate. Interested in the intricacies of marine structures and goal-based design aspects, he is dedicated to sharing and propagation of common technical knowledge within this sector, which, at this very moment, requires a turnabout to flourish back to its old glory.