Transgenesis may affect farm animal welfare: A case for systematic risk assessment

This paper considers (potentially) harmful consequences of transgenesis for farm animal welfare and examines the strategy of studying health and welfa re of transgenic farm animals. Evidence is discussed showing that treatment s imposed in the context of farm animal transgenesis are by no means biolog ically neutral and may compromise animal health and welfare. Factors posing a risk for the welfare of transgenic farm animals include integration of a transgene within an endogenous gene with possible loss of host gene functi on (insertional mutations), inappropriate transgene expression and exposure of the host to biologically active transgene-derived proteins, and in vitr o reproductive technologies employed in the process of generating transgeni c farm animals that may result in an increased incidence of difficult partu rition and fetal and neonatal losses and the development of unusually large or otherwise abnormal offspring (large offspring syndrome). Critical compo nents of a scheme for evaluating welfare of transgenic farm animals are ide ntified, related to specific characteristics of transgenic animals and to f actors that may interact with the effects of transgenesis. The feasibility of an evaluation of welfare of transgenic farm animals in practice is addre ssed against the background of the objectives and conditions of three succe ssive stages in a long-term transgenic program. Concrete steps with regard to breeding and testing of transgenic farm animals are presented, consideri ng three technologies to generate transgenic founders: microinjection, elec troporation and nuclear transfer, and gene targeting including gene knockou t. The proposed steps allow for unbiased estimations of the essential treat ment effects, including hemi- and homozygous transgene effects as well as e ffects of in vitro reproductive technologies. It is suggested that the impl ementation of appropriate breeding and testing procedures should be accompa nied by the use of a comprehensive welfare protocol, specifying which param eters to monitor, at which stages of the life of a farm animal, and in how many animals. Some prerequisites and ideas for such a protocol are given. I t is anticipated that systematic research into the welfare of farm animals involved in transgenesis will facilitate the use of the safest experimental protocols as well as the selection and propagation of the healthiest anima ls and, thereby, enable technological progress that could be ethically just ified.