manufacturing cheese or other dairy products. However, the largest investments in the technology to date have been made by pharmaceutical companies interested in producing enzymes, clotting factors, and other bioactive proteins in milk.
Companies also are interested in farm animals as possible sources of replacement organs for humans. Transplantation is an accepted and successful treatment for organ failure, but there is an enormous shortage of available human organs. As there are ethical and practical concerns related to the use of donor organs from primates, the pig, in particular, is being considered as an alternative. Unfortunately, humans express antibodies to a carbohydrate epitope (terminal 1,3-galactose residues) that is present on the surface of pig cells (Sandrin et al., 1993). As a result, the xenograft immediately becomes a target for acute rejection. To remedy this situation, pigs will be produced that lack the 1,3 galactosyl transferase enzyme (Tearle et al., 1996; Dai et al., 2002; Lai et al., 2002).
Although the mouse, because of its small size, short generation times, fecundity, and well-studied genetics has become the animal of choice for providing models for human disease, farm species might provide alternatives where the mouse is inappropriate. One possible future scenario is the creation of specific gene knockouts in farm animals in order to mimic human disease in a large animal model. For example, McCreath et al. (2000), have generated genetically-engineered sheep carrying a mutated collagen gene, and have suggested that such animals could serve as models for the human connective tissue disease osteogenesis imperfecta.
The development of such technologies and others yet to be conceived and their incorporation into agricultural and biomedical practice raises concerns about whether the end products can be consumed safely, whether there are likely to be unwanted effects on the environment, and whether animal welfare will be adversely affected. The goal of this report is to identify concerns that will aid the federal regulatory agencies in evaluating the possibility of such adverse outcomes. However, before proceeding further, it is perhaps helpful to understand what is meant by biotechnology and to appreciate how far such biotechnology already has been incorporated into current agricultural and biomedical practice. It also is clear that the concerns of the public are focused on some of the more recent technologic advances relating to gene transfer between organisms that would not normally interbreed and to assisted reproductive procedures, such as somatic nuclear cell transfer to create so-called clones (Eyestone and Campbell, 1999; Box 1.1). Many of these recent advances have not yet left the experimental stage, but it is clear that several, including transgenic finfish, which are soon likely to be commercialized, are likely to assume importance both in agriculture and medicine.