15/11/2012 09:37 GMT | Updated 15/01/2013 05:12 GMT

Farm Animals Have Become Grotesque Parodies of their natural selves. A case for the Vegan Option Continued

When factory farming first began at the beginning of the 1900s keeping large numbers of livestock in close confinement hugely increased the risk of disease. But in the 1940s the advent of antibiotics and pesticides made it possible to keep farm animals in vast numbers, densely packed together.

From then on animals were bred to grow ever faster and larger and ever more productive: more flesh, more eggs, more milk, larger litters. All that mattered was that they could survive long enough to reach their slaughter date - which is now 6 weeks for chickens, 7 weeks for ducks and between 4 and 9 months for pigs and lambs.

So changed are these animals that they have become aberrations of their natural selves. Pigs that have been bred to tolerate factory farm conditions now lack fat and hair to protect them against cold and sun and as a result are unable to tolerate outdoor life in extremes of weather. Poultry, genetically selected for their voracious appetites, suffer digestive disorders and obesity-related diseases and grow so fast their weight becomes, literally, crippling. Atlantic salmon, bred for sea cages, often have skeletal deformities (like hunched backs) and bleeding eyes. Cows have udders that weigh 50 to 75 kilos - more than their legs can adequately carry and makes lameness the dairy industry's most widespread welfare problem.

Another innovation is double-muscling. Animals like Belgian Blue cattle and Beltex sheep carry a genetic mutation where muscle growth continues uncontrolled. Not only do their offspring tend to be abnormally large but the extra muscle makes the birth canal smaller than normal. Other abnormalities include joint problems and skeletal deformities. These together with their unnatural bulk cause sore, cracked feet and weak legs and the consequence is chronic pain. Scientists are hoping to pass the double-muscle gene on to pigs and chickens as well.

And then there is cloning. Only about 30 out of 1,000 clones survive and most die before birth. But those that do survive tend to be bigger than their natural counterparts. Known as Large Offspring Syndrome (LOS), animals with LOS are inclined to suffer from kidney and brain malformations and impaired immune systems. Organs (like lungs and hearts) also tend to be abnormally big and a cause of more complications - like problems with breathing and blood flow. Although cloning is still at a developmental stage this could be the way animals are bred in the future.

With bodies too heavy for their bone structures and lacking the energy reserves of their traditional counterparts all animals that have been bred for the intensive farming industry have been pushed beyond their adaptive capabilities, not just physically but also psychologically. Yet despite all their physical changes their instincts and feelings are little different from the wild animals from which they are descended. Like all animals - including humans - they need a place where they feel safe and comfortable; mothers to care for them; to sleep normal hours; to eat a natural diet; and live free from anxiety, pain and fear.

The evidence of their suffering is in their behaviour. Given the choice pigs choose straw to bed down in, hens dust to roll in and ducks water to swim in. But when animals are reared in densely crowded, barren and utterly unnatural conditions they behave in ways which would be quite unnatural in a normal environment. Without the space to work out a pecking order pigs bite; cows kick; birds pull at feathers (and they have no place to escape when others attack them). When sows chew the bars of their crates or chomp at the air or endlessly turn their heads from side to side they are showing stereotypical behaviour: a sign of severe stress that in a human would be seen as a nervous breakdown. The perpetual raucous squawk of layng hens in battery cages must be for the same reason.

Factory farming is all about maximising profit to produce cheap food - hence the breeding of animals that have become grotesque parodies of their natural selves: malformed mutants, pushed to the limits. This is farming on a vastly cruel scale, the profit motive overwhelming any meaningful consideration of animal welfare.