|Photo © Greenpeace / Christian Lehsten|
The odds seem to be on sumo-wrestler-style pigs, cows and sheep.
These unfortunates grow an awful lot of lean meat because the gene which tells their muscles when to stop growing has been damaged.
More meat per animal equals more profit, and more of the 'healthy choice' lean meat we're told is the means more market.
Unfortunately more meat means bigger piglets/calves/lambs and that means birthing difficulties.
Also, they don't seem too healthy: in tests on super-muscly GM pigs, only 13 out of 32 piglets survived as long as 8 months. Of the remaining two who (presumably) are being allowed to live out their life-span, only one is considered healthy.
Of course, such animals would, in any case, be too few and too expensive to eat. The grand plan is to create a male with a complementary pair of the desired defective genes. Mating such a male with normal females will produce offspring with a single copy of the non-functional gene, lots of extra muscle (but not as much as their dad), and hopefully 'healthy' long enough to make it to the abattoir.
South Korean scientists who have created sumo-pigs using gene-editing  argue that their GM swine could, at least in principle, occur through a more natural route. (Note, not 'in nature' because the birthing difficulties would quickly eliminate any such mutation).
While the regulatory jury is still out on whether gene-editing is the same as gene-modification, the researchers are hoping to have free reign to capitalise on their invention.
GM livestock have one parallel with conventional breeding: the drive to enhance commercially useful traits to a physical extreme at the expense of animal welfare.
You are what you eat. Do you want food of this wildly distorted quality? If not, demand genetic-editing is seen for what it is, an extension of old-fashioned GM: such meat should never be on sale.
 GM SALMON APPROVED - January 2016
 SMART BREEDING TOOLS - OR HIDDEN GM? - January 2016
· David Cyranoski, Super-muscly pigs created by small genetic tweak, Nature, 523, 2.07.15