02/12/2012 13:07 GMT | Updated 30/01/2013 05:12 GMT

Humane Slaughter: A Contradiction in Terms? A Case for the Vegan Option Continued

Every day, all over the world, animals arrive at slaughterhouses by the truck, train and ship load - around 65 billion every year. That number is predicted to double by 2050.

Larger animals - cattle, sheep and pigs - are first driven into a 'stun box' to be rendered unconscious so that they remain unaware from then onwards. For cattle 'captive bolt ' pistols are fired at the centre of the head. They are stunned by the damage to the brain. Sheep, pigs and calves are usually stunned by placing electric tongs just below their ears. The electric charge drives through the brain and knocks them unconscious.

After they fall the animals are shackled by their legs and hung, heads down, from an overhead conveyor that carries them to the slaughtermen who cut their throats. To make sure the killing process is complete they are bled for 2 minutes before they are butchered.

That is the theory. In practice the stunning process often goes wrong. Alarmed by the shouts of workers and terrified by a raft of unfamiliar sights and sounds, animals panic. And in their panic they struggle. The vast number of animals that have to be processed means that the stunning is often botched. When this happens the animals regain consciousness as they hang suspended from the shackles on the way to the killing area.

Poultry (chickens, ducks, quail, turkey and geese) are rendered unconscious in a different way. The birds are hung on shackles first - also by their legs with heads down - and stunned afterwards. (Hanging like this must be painful, particularly for those that are lame, have broken bones or are heavy - think of butterball turkeys). The conveyor belt takes the birds over an electrically charged water bath so that their heads make contact with the water and they are stunned. Undercover observers (sent in by welfare organisations) have reported terrified birds lifting their heads as they pass over the electrified bath. Failing to make contact with the water means they remain fully aware as they are passed on to the rotating blades that slice off their heads.

But even the theory of electric stunning is flawed. Some animals need a higher voltage to stun them than others - ducks need more than chickens or turkeys for instance. The time that animals remain unconscious also varies. Studies show that calves that have been electrically stunned remain unconscious for less time than any other farmed animal - about 18 seconds. That means, since they take up to 2 minutes to bleed to death, many are likely to show signs of recovery while they are being bled.

Most animal welfare organisations have video footage of animals clearly conscious and struggling violently as they hang from shackles. Some studies suggest one fifth of animals might be fully conscious when they reach the knives.

But is there a way that animals could be despatched humanely? Could they be slaughtered without being panicked and improperly stunned as they hang painfully on shackles with the smell of blood and death all around them?

Organic certifiers have strict standards that are designed to minimize stress. For example transport to the abattoir must not take more than 8 hours and handlers are trained to deal with animals calmly and competently. Electric goads can only be used with special permission, and then only when required for human safety. On arrival at slaughterhouses waiting is kept to a minimum. Organic animals are always killed before their non-organic counterparts. Nevertheless the reality is that organic animals must also at some point sense what is going to happen to them.

Some small specialist producers have a licence to kill animals on the farm. These animals do not have to suffer the stress of being loaded onto transporters; they are not mixed with other panic-stricken animals; or driven long distances; or have to wait at the slaughterhouse. In the best case scenario, killing is instant. But when jobs are seasonal - like killing turkeys for Christmas for instance - and since training is not compulsory, killing (usually neck dislocation) might be done with little skill.

A great deal of research is in progress to make slaughter more efficient and less stressful for animals - in other words, more humane. Using carbon dioxide to stun pigs is one example (see ). Perhaps this CO2 method reduces the time that the animals have to suffer. But as they gasp for air it cannot be stress-free.

To be humane means to be kind, merciful and sympathetic. Is humane slaughter a realistic expectation?