Despite this low frequency, transgenic pigs carrying growth hormone (GH) gene from bovine (of 'ox' origin) or human, and sheep globin gene have been produced (by V.G. Purse) at Agriculture Research Service, Beltsville; USA.

The pigs carrying hGH gene showed different levels of expression and only 66% of these animals showed detectable levels of hGH and bGH in their plasma. The animals grew a little faster but did not become large; similarly pigs with sheep globin gene did not show any expression of the transgene for unknown reasons.

In these transgenic pigs, however, a modest increase of 10-15% in daily weight and 16-18% in feed efficiency was observed, which is though lower to those in mice, but are comparable to those obtained due to daily injection with pig growth hormone.

It was also observed that there was a marked reduction in the subcutaneous fat in some of these transgenic pigs suggesting the possibility of producing leaner meat with lower fat content. These results may have a significant impact on the 9.5 billion dollar annual pig industry in U.S.A.