Tamed

by Alice Roberts

  The film goes on to describe the state contests, though it’s hard to take this seriously – the accompanying jaunty music, ‘The Liberty Bell’ march, was later hijacked by Monty Python, of course. Then we’re on to chick embryology, with footage of chicken embryos developing inside their eggs, a section of eggshell removed at each stage to provide a window on their development.

  Back to racks of untampered-with eggs, as we’re told that all entries in the national final were incubated, hatched and raised under identical conditions. We see five men in suits from the poultry industry inspecting the chicks, approvingly. Then a woman in a pretty white blouse and a string of pearls pops up. Her dark hair is pulled up at the sides, and she’s wearing bright red lipstick. She’s also cupping two chicks in her hands – and then she lifts the chicks to her cheek and smiles. ‘Pretty chicks? Yes, sir!’ the voiceover comments, enthusiastically, as the double entendre misses its mark. After that light relief, it’s back to the men for the ‘enormous task’ of wing-banding the chicks with their flock number.

  We follow the chickens through their short twelve-week lives, as they grow into big, handsome birds, some brown, some with grey stripes, some white as snow. They get put into crates for transport, transferred to cages … and suddenly they’re carcasses hanging from hooks, ready to be judged. ‘Twelve birds from each of the samples were packed for display purposes. Others,’ the voiceover explains, ‘went on the eviscerating line.’ Here are women again, pushing along chickens strung up from their feet on what look like coat-hangers. One man is in there, inspecting the birds. Then we see the final display – a few exemplary cockerels in cages, and boxed-up chicken carcasses draped with lametta. But outside, something extraordinary is approaching: a chariot, covered in white fur, and flanked by two American flags, carrying a woman in a white robe, wearing a crown. Nancy McGee, described as a ‘supplementary attraction to the programme’, is the Del Marva Chicken-of-Tomorrow Queen.

  Still, Nancy doesn’t detract attention from the real champions for long. They’re the small flock bred by Charles and Kenneth Vantress, who crossed Red Cornish cocks with New Hampshire hens. It proved to be a winning combination, securing the Vantress brothers first place for both weight of birds, and efficiency of feed conversion into live weight (translating into more food for your money). But this is a beginning, not an end. The film isn’t there just to announce results, but to launch another national contest, to take place in 1951. More men in suits are looking pleased about the prospect of future competitions. The voiceover wraps it up, ‘Even today, housewives are enjoying improved meat-type chickens’ – and there are all the housewives, in a line, eating fried chicken thighs and drumsticks with their greasy fingers and grinning.

  This film was clearly made in a very different world. A world where only men did serious work, while women either held fluffy chicks to their cheeks and looked decorative, or did the boring, mundane jobs. It’s also a world where chickens were skinny things, while the poultry industry dreamed of making them what they are today: fast-growing, plump, white-fleshed monsters. The thing that hasn’t changed is the approach. Right from its inception, the breeding of broiler chickens was clearly, already, an industry. How telling that chickens are referred to, in the opening sentence of the voiceover, as a ‘crop’. And the genes of the winning chickens from 1948 are scattered amongst our commercial flocks today.

  The victorious Red Cornish cross from the contest was bred together with a white-feathered Leghorn which had won in the purebred category. The result, the Arbor Acre breed, became immensely successful. What had been a small farm focusing on fruit and vegetables, with a sideline in chickens, became the major supplier of America’s broiler companies. In 1964, Arbor Acres was bought by Nelson Rockefeller and exploded on to the global stage. Half of the chickens in China are descended from Arbor Acres lineages – descendants of the competition chickens. It sounds astonishing, and it’s hard to imagine how breeding has changed chickens so quickly, and so completely.

  The transformation of chicken production into an enormous global industry involved not only selective breeding on an unprecedented scale, but also extremely tight regulation of breeding. Today, chicken breeding and chicken rearing by farmers are completely separated. The very fact that chickens are laid in eggs which can be incubated by machines rather than hens allows for this complete division. Chicken farmers rear chickens – often on a huge scale – but they’re not the ones breeding the chickens. That task is carried out by breeders – and just two, huge multinational companies that dominate the market: Aviagen and Cobb-Vantress.

  These companies keep a very tight rein on their pedigree breeding-bird populations. Three generations down the line from their protected pedigree flocks, they create ‘parent stock’ which is sold to broiler-breeder farms, where chickens from separate genetic lines are bred together to make the final mix. The resulting chicks are sent on to broiler ‘Grow-Out’ farms – even your free-range, organic birds can come from those industrial chicken breeders, though there are some smaller breeding firms that specialise in slow-growing chickens for the traditional and organic market. Most chickens, though, grow fast – and are slaughtered at just six weeks old. When we eat chickens, they’re really just overblown, overgrown, big chicks. The ends of their bones haven’t even begun to turn from cartilage to bone yet. A single great-grandmother hen, back in the pedigree flock, can have an astonishing 3 million broiler-chicken descendants – who never make it to adulthood.

  As well as carefully controlling the characteristics of their pedigree chickens from a phenotypic point of view – scrutinising their growth trajectories, their weight, their feed consumption – chicken breeders are now using genomics to hone their selective-breeding techniques. But advances in genetics also hold out the possibility, not just of genotyping chickens, and identifying advantageous genetic variants, but of genetically modifying the birds. No commercial chickens have been genetically modified – yet. But the techniques are being tested out in research institutes. The tools to edit the DNA of chickens and other livestock – to remove deleterious pieces of DNA and to insert advantageous genes – already exist. It’s been an arduous journey just to get to the point where the method works. Now the race is on to find ways of using that method to improve flocks. And just a seven-minute drive from the beautiful fifteenth-century Rosslyn Chapel in Scotland, mythologised in Dan Brown’s The Da Vinci Code, is the Roslin Institute – where they’re busy investigating a different kind of bloodline, a different kind of code. I travelled to Midlothian to meet these new code-breakers.

  The researchers of Roslin

  The Roslin Institute is a suite of state-of-the-art buildings, some designed to contain chickens, to get the best out of them, and others designed to hold scientists – to get the best out of them. The scientists here are focused on optimising their chickens – and not just through selective breeding. That’s worked wonders on chickens over the last millennia, and then in a truly extraordinary way over the last sixty or so years. But now we can interact directly with the genetic code of an organism, selective breeding looks positively archaic in comparison. Domestication is a continuing process – and this is where the forefront of domestication currently lies.

  New techniques in genetic modification promise the earth – literally. With their help, we could be farming in a much more efficient, sustainable, egalitarian way in the future. And yet we’re afraid. Selective breeding is one thing, but for many direct genetic manipulation – using enzymes to modify DNA – seems a step too far, a Rubicon we should not dare to cross.

  Instinctively, I feel there could be something wrong here. Science fiction has primed me – even me – to be wary of genetically altered organisms. Novelist and journalist Will Self is a master of writing about uncomfortable, unsettling otherness. In his Book of Dave, there are genetically modified pig-like animals called ‘motos’ which are both pets and livestock. They are intelligent; they talk – in toddler-ish broken phrases – but they w
ill be slaughtered and eaten. The motos challenge our perception of the animals that we deliberately breed for consumption. We deem our tastebuds more important than their lives. There was too much dissonance there for me – I was completely vegetarian for eighteen years. Now I eat a little fish, managing my guilt, but other flesh is still a step too far.

  We create a division in our minds between us and other animals – a necessary division if we are to eat them. You’d never consider eating another human (I imagine). But most people don’t have a problem with farming animals, slaughtering them, and eating them. So what about changing them? This seems to be acceptable – if achieved through selective breeding. When it comes to plants, it seems we’re comfortable with the idea of creating mutations using radiation or mutagenic chemicals, then selectively breeding these genetic changes into our crops. If that sounds novel and dangerous, it’s actually something we’ve been doing regularly since the 1930s. More than 3,200 types of mutagenic plant have been created and released since then. Some of them are now grown and promoted as organic products. The majority of groundnuts grown in Argentina are bred from irradiated mutants. The majority of rice grown in Australia is bred on from an irradiated mutant type. Mutant rice is grown in China, India and Pakistan. Mutant barley and oats are widely grown in Europe. In the UK, Golden Promise barley, a mutant created by zapping plants with gamma rays, is grown to make beer and whisky. There’s no danger at all from the radiation in the crops that are being grown – it’s already done its work, scrambling DNA in their ancestors, and producing useful variants.

  These plants are, quite clearly, all genetically modified. So why is it more acceptable to modify genes using an instrument as blunt as a beam of gamma radiation, whilst using an enzyme to do the same sort of thing – in a much more precise and controlled way – feels like it could be more dangerous? The International Atomic Energy Agency is keen to separate ‘radiation breeding’ from biological, genetic modification. Radiation breeding is described as being simply an accelerated version of the spontaneous mutation that occurs in organisms and which is the stuff of variation, the lifeblood of evolution itself. But if we’re already modifying DNA using radiation, and calling that ‘radiation breeding’, it strikes me that we should be calling the – more exact and directed – biological version ‘enzyme breeding’.

  So I was keen to get inside the Roslin Institute and talk to the researchers themselves about their own take on genetic engineering, and the newest tools for doing it. They are pioneers, operating right at the frontier. They understand the science, as well as the swirling vortex of perception and prejudice and valid concerns, better than perhaps anyone else. And they know the genes of the chicken – the first domesticated animal to have its full genomes sequenced, back in 2004 – very well indeed. Adam Balic explained the techniques and their potential uses; Helen Sang talked to me generally about this science and the politics around it; and Mike McGrew told me about the exciting new developments – and his vision for this technology as a force for good in the world.

  Adam met me and escorted me up to his light-filled office on the first floor of the steel, glass and copper-clad building that houses the scientists at Roslin. There were posters showing the stages of chick embryological development on the walls. We sat down and he pulled up images on the screens that took up most of the space on his desk. There were islands of bright green glowing against a black background. These were photographs, taken down a microscope, showing a developing chicken embryo. We were looking at its neck, and the patches of green were showing up a specific type of tissue – lymphoid tissue, the same sort of stuff that makes up our own lymph nodes. This tissue doesn’t usually glow green: Adam had engineered the chicken embryo, inserting a ‘reporter gene’ into the chick’s genome that would produce a green, fluorescent colour wherever lymphoid tissue developed.

  He’d made this change to the embryonic chick’s DNA using a traditional method, or at least, one that’s been used for around twelve years in chickens. He’d used viruses to do the work for him. Many viruses work by inserting DNA into a host’s genome, and so it’s possible to hijack this mechanism, getting the virus to insert the gene that you’re interested in, into the cell of another organism. These ‘viral vectors’ were originally developed for human gene therapy, but they work well for chickens, too. Although it’s not generally possible to direct the virus to a specific position in the new genome, they seem to be pretty good at finding places to insert genes where that gene will have a good chance of being read, or expressed, by the cell.

  Adam was using this tried and tested technique to illuminate lymphoid cells in his chick embryos. The way he’d done it was to identify a protein that was normally made in those cells, but not in others, and then to find the ‘on-switch’ – the regulatory sequence of code that sits just upstream of the code for the protein itself. Then he could construct a new length of DNA – combining that particular ‘on-switch’ with a gene for making a green fluorescent protein – originally isolated from a jellyfish. Using a viral vector, Adam could insert that whole new package – the switch plus the jellyfish gene – into the chicken embryo. Then, in any cell where the switch was thrown to make the normal lymphoid-cell protein, the gene for the glowing protein would also be switched on. The genetically modified embryo obligingly ‘stained itself’, revealing its lymphoid tissue with stunning clarity, when illuminated with UV light under the microscope.

  ‘These aren’t just pretty pictures. They will allow us to quantify things too,’ Adam explained. The images showed precisely where lymphoid tissue – associated with the immune system – was developing in the embryo. Adam was studying the development of the chick immune system and these striking images were crucial to working out how the relevant immune cells and tissues formed. We were looking at how the chick’s defences were being laid out, almost like mapping ancient fortifications and trying to understand how a battle was fought. Birds have a very different immune system from mammals, so unusual in comparison that it prompts us to question how they’ve managed to survive without the tools that mammals have developed?

  ‘Almost everything we’ve learnt from mammals tells us that birds shouldn’t exist,’ said Adam, ‘but they cope with the same environment, the same pathogens – coming up with different solutions.’ Noticing differences like this, and trying to understand why those differences exist – that’s often how science proceeds. Lymph nodes seem so critical to mammals, including us. Birds possess patches of lymphoid tissue, but nothing as discrete and definite as a lymph node – and they manage perfectly well without them. It’s an interesting conundrum. Lymph nodes seem like quite complex things to invent. Why do mammals need them while birds don’t? By default, we’ll understand a lot more about the human immune system if we find out how birds manage to fight off infections with their quite distinct immune systems.

  Genetic modification has enabled embryological development to be mapped more precisely than ever – it was clearly an important tool for fundamental scientific research like this. But what about the applications for genetic modification that could take it, out of the lab, into chickens bred for food? The Roslin researchers were looking at that angle too, using the combination of a quirk of embryological development together with an astonishingly precise new gene-editing technique.

  Spreading a particular version of a gene through a flock of chickens relies on getting that gene into the cells which produce gametes – the eggs and sperm. The gamete-producing cells in the gonads of chickens (and humans) are known as primordial germ cells. They are essentially immortal cells – they will divide and divide, with some progeny ‘growing up’ into eggs or sperm, depending on the sex of the animal, and some staying as germ cells, ready to divide again – to make more eggs and sperm, and to replace themselves. The conventional way of getting your gene of choice into those primordial germ cells is indirect and more than a little haphazard – by selective breeding. You identify chickens with a particular trait, and breed those
chickens together, hoping that the gene for the trait is there in some eggs and sperm, and will make it into some birds in the next generation. It takes generations to spread a trait through a flock. But imagine if you could short-circuit that process, by ensuring that all the eggs of a hen or the sperm of a cockerel contained the desired gene – then all their offspring will have that gene and exhibit that trait, straight away. This is precisely what the newest gene-editing tool allows the geneticists to do. And, serendipitously, it’s relatively easy to remove primordial germ cells from a chick embryo, in order to modify them.

  Chicks have fascinated embryologists ever since Aristotle followed the three-week development of hens’ eggs. It’s possible to raise a section of the eggshell and to observe the developing embryo – and even interact with it – without killing it. The embryo develops on one side of the ovum – and you’ll be familiar with what that ovum looks like. Before it gets covered in albumen, and a shell, it’s the yellow bit that is mostly a massive yolk.