A clarification on why animals fed GM are more likely to drop dead in the lab than in the field.
In August 2012 we reported that, during two livestock feeding trials of Syngenta's 'Bt176' GM maize, in America and Germany, some of the cows sickened and died; the illness was never identified (see DEAD COWS UNDER THE CARPET - August 2012).
These unexpected events during tests haven't translated into widespread deaths in the field when animals have been given feed containing Bt176 corn, or other GM crops with the same artificial gene (cry1Ab).
It's been drawn to our attention that our explanation of why the laboratory and field studies could give such different results was too concise. So, in the interests of clarity, here's a fuller description.
There's no information on the American study in which test-animals died, but the German cows were fed increasing rations of Bt176 until, by the 3rd year, they were getting only the GM corn in their feed. The problems started the following year, and got worse the year after. This suggests that consistent, prolonged feeding with a single GM crop, Bt176, may be linked to serious ill-health.
A typical commercial herd will be fed on various feed formulations made from whatever type, and in whatever proportions, of commodity corn happen to have rolled off the production line. The animals will rarely be given feed with completely identical ingredients for any length of time, and four years in a row would be very rare indeed.
To give some idea of the scale of the variety of corn strains which could go into the mix, the European Commission has authorised importation of twenty-seven different GM maize varieties, containing one or more of eight different Bt genes. Add to these, at least one strain containing a 'vip' insecticide-producing gene, a multitude of herbicide-tolerant versions, and the odd genetic marker (such as ampicillin resistance) as a production aid.
Bt176 and eight other Bt corn varieties imported into the EU contain cry1Ab genes. These eight other crops aren't directly related to Bt176: the DNA constructs are different and they're inserted in different places in the genome. Some of these might be safe, some might cause harm, they all might be safe, they all might be harmful. But, if you feed them to animals in varying quantities and varying combinations for varying lengths of time, and mix them with unknown proportions of eighteen other GM maize varieties plus the unknown proportions of unknown conventional maize (Bt crops are supposed to planted with a 20% 'refuge' of non-GM maize), it's unlikely you'll see a single, clear problem consistently enough to make a definite link to any one GM maize type.
And, there's another great unknown in GM animal feed: Bt176 (and possibly all GM maize) seems to be unstable.
Bt176 corn is supposed to contain a DNA construct with two copies of cry1Ab. In 2003, molecular studies of several GM crops in the EU found that the artificial DNA constructs had rearranged and in some cases altered the host plant's DNA. The putative cry1Ab gene in Bt 176 turns out to be more similar to cry1Ac. Cry1Ac is not authorised for use in Europe and the protein it generates has been identified as a potent systemic and mucosal immunogen, as potent as cholera toxin. It was also found that, whatever the Bt gene in Bt176 plants actually is, it seems to have expended itself to 4-5 copies. Bt 11 maize, which is still on the market and also contains a cry1Ab gene, was found on molecular analysis to have incorporated extra chunks of bacterial and maize DNA. Also, Bt11 seems to be contaminated with Bt 176.
The length of time it took for the German cows to sicken suggests some cumulative toxic effects may be present in Bt176. If the animals have been fed on ever-changing commodity corn, there would probably be little opportunity for accumulation.
However, the apparent harmful effects of Bt176 might not be directly due to any toxic qualities in the feed. Interference with the digestion or changes in gut microflora due to prolonged exposure to this maize are strong alternative candidates.
Besides providing a novel substrate for pathogenic microbes to feed on, horizontal gene transfer from Bt176 (especially in light of its instability) could generate novel bugs which don't support health. Such effects are less likely to become evident in herds fed on more varied maize-types, where the pressure on the gut flora to change will not be constant.
On the subject of gut microbes or nutritional interference, there's plenty of scope for undetected general weakening of the animals. While livestock aren't kept alive long enough to suffer much chronic disease as humans will, susceptibility to infection is a more likely symptom. Infections will be routinely treated with antibiotics or vaccines, or by killing any vectors identified: the connection with GM feed will not be made.
The trick to 'proving' safety is to create so much back-ground noise that any ill-effects will be drowned out.
The claim that GM food has been 'proven' safe because 300 million Americans have been eating it for decades without evidence of harm is as tenuous a proof of safety as the lack of deaths in GM-fed cattle. Just think what all those American guinea-pigs are actually eating: a vast variety of processed GM junk. Chronic disease has been rising for years: who could possibly pin any blame on GM food?
Back-ground noise can cover up a huge groundswell of disease and death.
Note. Colorado State University information on Bt176 corn tells us that it was withdrawn in America in 2001 ostensibly because it afforded poor protection against the European corn borer later in the season. This was also the year that Syngenta got their second hint that the corn killed cows.
- Transgenic crops discontinued, Colorado State University, December 2004 http://cls.casa.colostate.edu/transgeniccrops/defunct.html
- Unstable Transgenic Lines Illegal, Institute of Science in Society Report, 3.12.03
- EU register of genetically modified food and feed, EU Register of authorised GMOs, European Commission DG Health and Consumers