and particularly its practical application, comes from the work of Temple Grandin in North America (Grandin, 1991). An excellent series of papers covering various aspects of the handling of livestock both during transport and in slaughter plants is given in Grandin (1993).
The harvesting of poultry consists of catching the birds and placing them in transport crates (cooping). Broiler chickens are mostly reared on litter such as wood shavings in sheds housing many thousands of birds. Hens are often housed in battery cages and removal from these at the end of their laying life is more difficult than catching broilers. Older designs of battery cage do not allow easy access. Catching hens from
‘alternative’ systems, such as percheries, which give the birds more choice of movement, is also difficult because of the large amount of furniture, perches and nest boxes which restrict access.
Birds are picked up manually by teams of catchers or by mechanical
‘harvesters’ in which rotating rubber fingers collect and encourage the birds onto moving conveyors (Berry et al., 1990). There is considerable economic pressure to harvest birds quickly so that it is difficult to accord to each individual the care that is desirable to prevent physical damage. Mechanical harvesters may help to reduce damage although little information is available on the extent of the improvement.
The crates may be loose or form the drawers of ‘modules’. A module is a metal framework that can be handled and loaded onto a flat bed lorry by a forklift truck. The crates are of different heights for the different species, for example they are taller for turkeys. A module might carry 12 drawers each holding 20–25 broilers. A single vehicle might transport 6000 birds. The closely stacked crates restrict airflow and ventilation may be poor. Birds on the inside of a load may suffer hyperthermia while those on the outside may become very cold. In cold weather, side curtains may be used to protect these birds. However, there is a high probability of thermal stress being suffered by at least some birds in transit (Webster et al., 1993; Kettlewell et al., 1993).
Animals may be sent directly from the farm or production unit to the slaughter plant, or may be sold via collecting stations or live auction markets. The latter options increase the time between leaving the farm and slaughter, and the chances of different groups of animals being mixed together. The introduction of computer auctions, where animals are sold based on a description, and without the need to take them to central collection points, may be beneficial if the duration of handling is thereby reduced.
Times spent between leaving the farm and slaughter
Animals can spend considerable times in transit. Total marketing times of over 12 h have been recorded for poultry, and times over 30 h for
pigs and sheep in the UK (Warriss, 1992). Marketing times for cattle reared extensively under ‘range’ conditions can be very long. In Australia, such animals may travel for up to 2 weeks. Pigs have been exported from The Netherlands in northern Europe to southern Europe, journeys of 1500 km that can take up to 40 h. As the slaughter- ing industry in many countries becomes centralized into fewer, larger plants, marketing times and the distances animals must travel to slaughter are likely on average to increase and will tend to continue to do so.
On arrival at the plant, animals are held for various lengths of time before slaughter in a lairage or stockyard. They need to be supplied with water and, if appropriate, bedding and food. Generally, the conditions in the lairage need to be conducive to the animals resting so that ideally they recover from the rigours of transport. Most animals spend between 1 and 24 h in lairage. In some countries a minimum period – often 24 h – is prescribed, in others a maximum. In the UK the maximum time is 72 h.
The stresses associated with marketing
Even when carried out with care and consideration the marketing process is inherently stressful to animals in that it involves removal from their home environment, loading and unloading onto vehicles, often long journeys and holding in unfamiliar surroundings. This results in their being potentially exposed to physical stresses such as extremes of temperature, vibration and changes in acceleration, noise, confinement and crowding. There are also psychological stresses such as the breakdown of social groups and mixing with unfamiliar animals, unfamiliar or noxious smells and novel environments. Because animals are not usually fed before and during transport, and because water may not be available all the time, they may suffer from hunger, thirst and fatigue.
The effects on carcass and meat quality
The way the animal responds to these stresses, and the effects associated with them, can influence carcass and meat quality. In many cases, carcass quality equates to carcass yield and is therefore relatively easy to relate to economic loss. For example, total loss results if an animal dies during transport. Losses of variable size may occur if the carcass is damaged through bruising, haemorrhage, fighting or other trauma necessitating removal of the damaged tissue. Smaller, but economically significant losses occur if animals are subjected to a
period of food or water deprivation and the stresses associated with transport. The most commonly recognized consequences of poor pre- slaughter handling on lean meat quality are pale, soft, exudative (PSE) meat in pigs and dark, firm, dry (DFD) meat in pigs and cattle. The full economic consequences of lean meat quality defects are difficult to quantify accurately.