and the surrogate dam carrying the pregnancy. Emphasis was placed on the clones' development and probability of normal development, compared with other ARTs such as artificial insemination (AI), in vitro fertilization (IVF), and blastomere nuclear transfer (BNT). In our assessment of animal health, we considered a wide range of hazards, ranging from macroscopic to biochemical changes (e.g., changes in gene expression, differences in enzyme activity) that might affect the well-being of animal clones. For food consumption risks, animal clones bearing gross anomalies were excluded from the analysis, and emphasis was placed on identifying unique subtle hazards that could have arisen as the result of the SCNT process. The rationale for this approach is found in Chapter IV, and provides the molecular evidence for the role of epigenetic reprogramming as the source of these subtle hazards. Because of the assumption that hazards would be subtle, datasets were evaluated on as fine a level of resolution as possible, including individual animals or even individual analytes per animal in order to have as sensitive a screen as possible for adverse outcomes (and thus potential food consumption risks). In this risk assessment, the most detailed level of resolution used for evaluating animal health has been physiological and biochemical measures of individual animals. It is likely, as technologies mature, that molecular techniques such as genomics, proteomics, and their integrated metabolomic measures will assist in such determinations (NAS 2004).
Compositional Analysis: To reach conclusions about the risks of consuming food produced by animal clones, findings regarding animal health (derived from the CBSA) were considered in conjunction with results of the Compositional Analysis approach. In an attempt to find potential subtle hazards, the data considered in this part of the risk assessment included measurements of gross composition (e.g., carcass composition, percent fat and protein) as well as detailed analyses of vitamins and minerals, fatty acid profiles, and protein characterization of meat and milk produced by clones. The composition of foods produced by clones was compared to the composition of foods produced by comparator animals, and also to published reference ranges for meat and milk. These comparisons formed the basis of our determination of whether meat or milk from clones differs materially from meat or milk from conventional animals, and thus contributed to the overall conclusions regarding food consumption risks.
Weight of evidence: Weight of evidence evaluations do not rely on a single study or even a subset of studies. Instead, they are based on expert judgments on all of the information gathered in the course of a risk assessment. This allows for variability in the amount of information on any particular aspect of the evaluation, as well as inconsistency in endpoints evaluated. Chapters IV, V, and VI contain detailed descriptions of studies that were considered relevant to the hazard identification and characterization, and subsequent risk evaluation. For each adverse outcome identified, the empirical evidence for the causal association of cloning with that outcome was weighed against the empirical evidence indicating that there were associations with other causal agents or processes.
Animal Cloning: A Risk Assessment
