Transgenic Pigs - The rate of transgenic production in pigs, sheep, cattle and goats is much lower (usually <1 %) than that in mice (usually between 3-6%). In addition, swine ova contain a large amount of lipids, which makes the visualization of male pronuclei very difficult. Centrifugation of pig ova facilitates visualization of the pronuclei, which enables, microinjection of DNA into the male pronuclei.

The objectives in transgenic swine production are
(1) increased growth and meat production, and
(2) to serve as bioreactors.
Transgenic pigs expressing human growth hormone do show improved growth and meat production, but they also show several health problems. Several human genes have been expressed in swine with a view to harvest their protein products; these proteins were either secreted in milk or in blood serum from where they are easily recoverable.