New studies find the immune systems of young cloned pigs do not fight disease as effectively as those of regular pigs.
The research was conducted by the U.S. Department of Agriculture and the University of Missouri.
The scientists gave a naturally occurring toxin to seven young, cloned pigs and 11 genetically similar, non-cloned pigs. The cloned pigs' immune system did not produce sufficient quantities of natural proteins called cytokines, which fight infections.
As newborns, both the cloned and non-cloned pigs received some disease protection through their consumption of colostrum, a natural substance passed to a newborn pig via its mother's milk. The colostrum helps protect the young animal until its own immune system begins to function.
Cloned pigs, as well as cloned cows, have been known to have a higher-than-normal number of deaths around the time of birth. Many die from bacterial infections, the scientists said.
The cloned pigs are being used only for research purposes and won't be used for human consumption, the scientists noted.