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The word most commonly used to describe the current state of cat and dog cloning is "inefficient," which translates into the use of large number of animals to produce very few, if any, surviving offspring. In most cases, to clone an animal, eggs (oocytes) are surgically removed from female animals, manipulated in a lab to produce embryos, and surgically implanted into another group of female animals in the lab. Most will not develop pregnancies, and of those who do, few will give birth to offspring who survive.
The chart below illustrates all of the papers published worldwide that describe domestic cat and dog cloning experiments. Most of the experiments were conducted in South Korea and the rest were in the U.S.
Published Domestic Dog and Cat Cloning Experiments and Outcomes
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The public hardly hears about animal cloning failures. However, in discussions and papers published about cloning, it has become apparent that animals suffer a variety of consequences in cloning experiments.
One pet cloning firm claims that a new chromatin transfer (CT) technique is an improvement to nuclear transfer (NT) and claims that it has exclusively licensed the technique for cat and dog cloning. Citing a paper
on its website that discusses CT experiments and cattle cloning, the company states that CT will increase the survival of cloned pets. However, the study shows that CT resulted in no improvement
over nuclear transfer in pregnancy rates, embryo survival, or survival rates at birth. CT has also not been evaluated as improving physical or behavioral similarites between original and cloned animals or increased survival of cloned animals beyond one month of life.
A review of the success of CT in the cattle cloning article reveals that two groups of cattle were used: one group of 506 cows had multiple NT cloned embryos implanted into them, and a second group of 273 cows were implanted with multiple CT cloned embryos. Pregnancy rates and numbers of live calves at birth were the same for both groups. Forty-six calves (i.e., 9 percent survival of cloned embryos) were born alive through NT alone, and 27 (i.e., 10 percent survival of cloned embryos) calves were born through CT, indicating that there is no statistically significant improvement in fetal survival between the two groups. However, the authors report that at one month postpartum, 26 calves (i.e., 5.1 percent survival of cloned embryos) from the NT group and 23 calves (i.e., 8.4 percent survival of cloned embryos) from the CT group were still alive. Though it may appear that CT will facilitate, in the authors’ words, “a trend toward survival enhancement,” 8.4 percent is an extremely low survival rate. Thirty-two calves died at birth (15 of whom were from the CT group), and 24 calves died under the age of four weeks (four of whom were from the CT group). The fate of the calves living beyond four weeks is unknown.
Harm to Animals
Two well-known scientists in the animal cloning field are Ian Wilmut of the Roslin Institute in Scotland and Gerald Schatten of the Magee Women’s Hospital/University of Pittsburgh School of Medicine. Wilmut was credited with cloning Dolly the sheep. Schatten was credited with the first ever ‘successful’ genetic modification of a monkey, ANDi, and he is now actively trying to clone monkeys. Both men, along with other scientists, continue to remind the public and the scientific community of the common failures of animal cloning, particularly within the context of human cloning.
A published letter co-authored by Schatten and Wilmut in the journal Science
stated, “…animal cloning so far results in high rates of abortions and neonatal losses. Attempts to produce children…would be grossly irresponsible because the outcome would almost certainly include late abortions, stillbirths, and children with abnormalities that would prevent them from leading a normal life. Many cloned animals display birth defects, including respiratory failure, immune deficiency, and inadequate renal function—all leading to premature deaths.…”
Another paper published in Science
stated, “In all mammalian species where cloning has been successful, at best a few percent of nuclear transfer embryos develop to term, and of those, many die shortly after birth….Even apparently healthy survivors may suffer from immune dysfunction or kidney or brain malformation, perhaps contributing to their death at later stages. Most frequently cloned animals that have survived to term are overgrown, a condition referred to as "large offspring syndrome."
“Many cloned animals display birth defects, including respiratory failure, immune deficiency, and inadequate renal function—all leading to premature deaths…”
(Schatten, G., Prather, R., and Wilmut, I. Science, 1/17/03.)
A 2002 report from the National Academy of Sciences stated, “…[I]t is quite clear that across multiple species there are far more failures in the development of cloned fetuses than there are live normal births…The most notable defects are increased birth size, placental defects, and lung, kidney, and cardiovascular problems. Other problems have included liver, joint, and brain defects, immune dysfunction, and postnatal weight gain. Thus, a wide variety of tissues and organs can fail to develop properly in cloned animals…Animal cloning can also result in danger to the mother of any cloned offspring.”
A recently published paper on African wild cat cloning reported that 50 domestic cats were used in a cloning experiment that resulted in seven stillborn kittens, eight kittens who died before six weeks of age, and only two surviving kittens.
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See also: Animal Welfare
Sullivan, E.J., Kasinathan, S., Kasinathan, P., Robl, J., and Collas, P. 2004. Cloned calves from chromatin remodeled in vitro. Biology of Reproduction
Schatten, G., Prather, R., and Wilmut, I. 2003. Cloning Claim Is Science Fiction, Not Science Science
Rideout, W.M., Eggan, K., and Jaenisch, R. 2001. Nuclear Cloning and Epigenetic Reprogramming of the Genome Science
U.S. Committee on Science, Engineering, and Public Policy, et al. 2002. Scientific and Medical Aspects of Human Reproductive Cloning.
National Academy Press.
Gómez, M.C., Pope, C.E., Giraldo, A., Lyons, L.A., Harris, R.F., King, A.L., Cole, A., Godke, R.A., and Dresser, B.L. 2004. Birth of African Wildcat Cloned Kittens Born from Domestic Cats. Cloning and Stem Cells