Daisy chains and fluorescent pets
For better or worse, the genetic modification of animals is becoming easier and more precise. A suite of modified animals are making an appearance, from modified livestock to model organisms for scientists and unique pets for consumers.
Fluorescent fish have come a long way from their origin in a research laboratory. Modified zebrafish are available for sale in Asia and some parts of the US. These aquarium fish, dubbed the GloFish, glow in red, green and yellow — the result of inserted genes from corals and jellyfish. Not surprisingly, the fish are not approved for sale in Australia, Canada, California or Europe.
Genetic modification of livestock is one take on how to improve animal welfare and decrease suffering known to take place in large-scale industrial stockyards. Take the pre-plucked chicken:
“There’s interest in breeding this trait into fast-growing broiler chickens, to create birds that are less prone to heat stress and do not require plucking”.
While such a trait appears to offer an alternative to stressors of factory farming, breeding chickens for a single trait has been shown to cause a series of unexpected consequences. For example, chickens selectively bred for high egg production use much of their calcium to produce egg shells. The result are hens with weak skeletons, brittle bones and difficulty bearing their own weight. These hens often fracture bones during typical movements like standing, walking or hopping.
Approximately 35% of all mortalities among caged hens were attributable to bone fragility, known as cage layer osteoporosis (1).
And animals continue to be relied upon for scientific research. The diversity in research animals has boomed, with cats, marmosets and pigs replacing mice as model organisms in some studies. Pigs are particularly of interest in the study of human diseases like cystis fibrosis and high cholesterol. Because pig hearts and arteries are similar in size to those of humans, modified pigs are considered realistic “testbeds” for stents and other medical devices.
Pigs are also the focus of xenotransplant research, as they are considered to be the source of an unlimited supply of organs needed by humans awaiting transplants. Pig-to-human organ transplants have hitherto been unsuccessful because the human immune system recognizes the organs as foreign and rejects them. It is thought that humans may be more tolerant of transplants from modified organisms; silencing the expression of molecules in pigs may be the key. Interestingly, some xenotransplant research is being tested on monkeys. Organs are grown in a pig that is sacrificed, then transplanted into a monkey that will not survive more than 180 days after the operation. What a gruesome daisy chain of animal testing…that has yet to benefit humans.
1. McCoy. M.A., Reilly, G.A.C., and Kilpatrick. D.J. 1996. Density and breaking strength of bones of mortalities among caged layers. Research in Veterinary Science. 60: 185-6