Transgenic Sheep - Transgenic sheep have been produced to achieve better growth and meat production as well as to serve as bioreactors. For example, human genes for blood clotting factor IX and for α1-antitryspin have been transferred in sheep and expressed in mammary tissue; this was achieved by fusing the genes with the mammary tissue specific promoter of the bovine β-lactoglobulin gene.

Human growth hormone gene has also been introduced in sheep in order to promote growth and meat production. The transgenic animals showed improvements in body weight gain, feed efficiency, lean meat/fat ratio, fat composition, etc.

However, they also showed several undesirable effects like joint pathology, skeletal defects, gastric ulcers, infertility, etc. These problems have been attributed to chronic over expression of the growth hormone transgene.