Animal Cloning: A Risk Assessment

by the U.S. Food and Drug Administration

Animal Cloning:
A Risk Assessment

 

Center for Veterinary Medicine
U. S. Food and Drug Administration
Department of Health and Human Services
7500 Standish Place
Rockville, MD 20855

1/8/2008

 

Table of Contents

Preface		i
Chapter I: Executive Summary		3
A.	Overview	3
B.	Technology Overview (Chapter II)	4
C.	Risk Assessment Methodology (Chapter III)	5
D.	The Implications of Epigenetic Reprogramming for Clones and their Progeny (Chapter IV)	8
E.	Risks to Animals Involved in Cloning (Chapter V)	9
F.	Food Consumption Risks (Chapter VI)	11
	1. Two-Pronged Approach to Identifying and Characterizing Food Consumption Risks	11
	2. Conclusions Regarding Potential Food Consumption Risks	11
	a. Cattle Clones	11
	b. Swine Clones	13
	c. Sheep Clones	14
	d. Goat Clones	14
	e. Clone Progeny	14
G.	Concluding Statements (Chapter VII)	15
Chapter II: Technology Overview: Somatic Cell Nuclear Transfer and Other Assisted Reproductive Technologies		19
A.	What is Cloning?	20
B.	Continuum of Reproductive Technologies	21
	1. Natural Service	21
	2. Artificial Insemination and Synchronized Estrus	22
	3. Embryo Transfer	25
	4. In vitro Fertilization	26
	5. Embryo splitting	27
	6. Blastomere Nuclear Transfer	28
	7. Somatic Cell Nuclear Transfer (SCNT)	29
	a. Donor cell	30
	b. Oöcyte	31
	c. Fusion	31
	d. Transfer to recipient	32
C.	Critical Biological Events in SCNT	33
D.	Outcomes Observed in ARTs	35
E.	Future of Reproductive Technologies in Modern Agricultural Practice	36
Chapter III: Developing the Risk Assessment Methodology		41
A.	Charge	41
B.	General Discussion of Risk/Safety Analyses	41
	1. Risk and Safety	41
	2. Risk Assessment vs. Risk Management	42
C.	Risk/Safety Assessment of Cloning	42
D.	Transgenic Animal Clones	44
E.	Methodology Development	45
	1. Hazard Characterization	46
	2. Potential Risks	47
	3. Proposed Approaches	48
	a. Animal Health Risks	48
	b. Food Consumption Risks	49
F.	Two-Pronged Approach to Assessing Food Consumption Risks	50
	1. Critical Biological Systems Approach	51
	a. Overview	51
	b. Evaluation Nodes	52
G.	The Weight of Evidence Approach	54
H.	Limitations of the Risk Assessment	55
Chapter IV: Epigenetic Reprogramming: Implications for Clones and their Progeny		59
A.	Overview of Epigenetic Reprogramming in Early Embryonic Development	61
	1. Preimplantation Reprogramming	63
	a. Fusion and Cleavage	63
	b. Demethylation and Remethylation in Early Embryos	66
	c. Epigenetic Reprogramming in Later Development	70
	d. Studies of Gene Expression and Development in Clones and Animals Produced by Other ARTs	73
	e. Studies of Technical Contributions to Epigenetic Variability in Clones and Other ARTs	78
	2. Gametogenic Reprogramming	79
	3. Mitochondrial Heteroplasmy	81
	4. Conclusions from Studies of Epigenetic Reprogramming	82
B.	Phenotypic Evidence for Gametogenic Reprogramming	83
	1. Phenotypic Anomalies Observed in Mouse Clones	83
	a. Utility of Mouse Model	83
	b. Pregnancy (Developmental Node 1)	84
	c. Perinatal Period (Developmental Node 2)	86
	d. Juvenile Period to Reproductive Maturity (Developmental Nodes 3 and 4)	86
	e. Maturity and Aging (Developmental Node 5)	88
	2. Conclusions from Phenotypic Studies of Gametogenic Reprogramming in Mouse Clones and their Progeny for Reprogramming in Domestic Livestock Clones and their Progeny	90
C.	Implications of Epigenetic Reprogramming for Animal Health and Food Consumption Risks	91
Chapter V: Animal Health Risks		95
A.	Potential Hazards and Risks to Animals Involved in Cloning	95
B.	The Critical Biological Systems Approach to the Analysis of Clone Animal Health: Cattle, Swine, Sheep, and Goats	96
	1. Pregnancy and Parturition (Developmental Node 1)	96
	2. Perinatal Period (Developmental Node 2)	98
	3. Juvenile Developmental Node (Developmental Node 3)	99
	4. Reproductive Development and Function Node (Developmental Node 4)	100
	5. Post-Pubertal Maturation and Aging (Developmental Node 5)	101
	a. Telomere Length as an Indicator of Aging	101
C.	Data on Animal Health by Species	105
	1. Cattle	105
	a. Developmental Node 1: Pregnancy and Parturition	109
	b. Developmental Node 2: Perinatal Period	123
	c. Developmental Node 3: Juvenile Development	135
	d. Developmental Node 4: Reproductive Development and Function	145
	e. Developmental Node 5: Post-Pubertal Maturation and Aging	150
	f. Progeny of Bovine Clones	153
	g. Summary for Health of Bovine Clones and Their Progeny	156
	2. Swine	157
	a. Developmental Node 1: Pregnancy and Parturition	158
	b. Developmental Node 2: Perinatal Period	159
	c. Developmental Node 3: Juvenile Development	163
	d. Developmental Node 4: Reproductive Development and Function	165
	e. Developmental Node 5: Post-Pubertal Maturation and Aging	166
	f. Progeny of Swine Clones	166
	g. Summary for Health of Swine Clones and Their Progeny	167
	3. Sheep	168
	a. Developmental Node 1: Pregnancy and Parturition	169
	b. Developmental Node 2: Perinatal Period	172
	c. Developmental Node 3: Juvenile Development	174
	d. Developmental Node 4: Reproductive Development and Function	175
	e. Developmental Node 5: Post-Pubertal Maturation and Aging	175
	f. Progeny of Sheep Clones	176
	g. Summary for Health of Sheep Clones	176
	4. Goats	176
	a. Developmental Node 1: Pregnancy and Parturition	177
	b. Developmental Node 2: Perinatal Period	178
	c. Developmental Node 3: Juvenile Development	179
	d. Development Node 4: Reproductive Development and Function	180
	e. Developmental Node 5: Post-Pubertal Maturation and Aging	180
	f. Progeny of Goat Clones	180
	g. Summary for Health of Goat Clones	181
D.	Conclusions	181
Chapter VI: Food Consumption Risks		187
A.	Potential Hazards and Food Consumption Risks Associated with Food Products from Animal Clones and their Progeny	187
	1. Assumptions	187
	2. Critical Biological Systems Approach to Clones of Cattle, Swine, Sheep, and Goats	188
	a. Bovine Clones	188
	b. Swine Clones	243
	c. Sheep Clones	260
	d. Goat Clones	264
	3. Compositional Analysis Method	268
	a. Overview	268
	b. Nutritional Risk	269
	c. Characterization of Milk from Cow Clones	278
	d. Characterization of Meat from Clones and Their Progeny	288
B.	Drawing Conclusions Regarding Risks Associated with Consumption of Food Products from Animal Clones	309
	1. Approaches for Decreasing Uncertainties	309
	2. Bounding the Risk Space	310
	3. Developing Conclusions Regarding Food Consumption Risks	310
	4. Weight of Evidence Conclusions Regarding Food Consumption Risks for Clones and their Progeny	312
	a. Cattle Clones	312
	b. Swine Clones	316
	c. Sheep Clones	317
	d. Goat Clones	318
	e. Clone Progeny	319
	5. Summary of Risk Hypotheses	319
	a. Additional Issues	320
	6. How Much (Information) Is Enough?	323
Chapter VII Summary and Conclusions		327
A.	Methodology	327
B.	Conclusions Regarding Risks to Animal Health	328
C.	Conclusions Regarding Food Consumption Risks	329
D.	Conclusions Regarding Food Consumption Risks from Clone Progeny	330
E.	Weight of Evidence Evaluations	330
Glossary		333
References		349
Appendices
Appendix A: Risk and Safety Assessment Primer for Animal Cloning		425
A.	How has Risk Assessment Evolved?	425
B.	Thinking About Risk	426
C.	How Do We Think About Safety?	428
Appendix B: Overall Reproductive Efficiency and Health Statistics for US Animal Agriculture		431
A.	Dairy cattle	431
B.	Beef Cattle	433
C.	Swine	436
D.	Sheep	437
D.	Goats	439
Appendix C: Comparisons of Outcomes Among Assisted Reproductive Technologies (ARTs)		443
A.	Successes and Failures of AI, IVP, and ET	449
B.	Outcomes for BNT, Fetal- and Adult-Cell SCNT	453
C.	Conclusions regarding outcomes for ARTs	454
Appendix D Transgenic Clones		457
A.	Issues	457
B.	Cattle	458
C.	Swine	460
D.	Sheep	462
E.	Goats	463
F.	Conclusions Regarding Transgenic Clones	466
Appendix E: The Cyagra Dataset		471
A.	Response to CVM Data Requests	471
B.	Cyagra Dataset	472
	1. Description of Clones	474
	2. Evaluations Performed	476
	3. CVM's Analysis of Cyagra Data: Method	477
	4. CVM's Analysis of Cyagra Data: Results	479
	a. Comprehensive Veterinary Examinations	479
	b. Conclusions from Veterinary Examinations	480
	c. Laboratory Values: Selection of Most Appropriate Comparator	481
	d. Conclusions Regarding Clone and Comparator Population Cohorts in Aggregate	482
	e. Animal and Analyte Specific Analyses	484
	f. Animals with Measurements at Different Developmental Nodes	487
	5. Charts and Tables	500
Cyagra Data Chart Interpretations		501
Cyagra Raw Data		523
Appendix F: The ViaGen Dataset		571
A.	Background	571
B.	Experimental Design	571
	1. Study 1: Clones vs. Comparators	573
	a. Animal Health, Hematology, Clinical Chemistry, and Urinalysis	574
	b. Boar Semen Evaluation	574
	c. Farrowing Rate	574
	2. Study 2: Progeny of Clone Boars vs. Progeny of Conventional Boars	575
	a. Statistical Analysis	575
	b. Specific Methods for the Analysis of Animal Health, Hematology, Clinical Chemistry, and Urinalysis Data	578
	c. Meat Composition, Carcass Characteristics, and Meat Quality Assessments for Clones, Comparators, and Progeny	578
C.	Results	579
	1. Study 1	579
	a. Survival	579
	b. Animal Health, Growth, Blood Clinical Chemistry, Hematology, and Urinalysis	580
	c. Carcass Characteristics	588
	d. Meat Composition Analysis for Clones and Comparators	589
	e. Semen and Breeding Evaluation	591
	f. Farrowing Rate	592
	2. Study 2: Progeny of Clones vs. Comparators	594
	a. Survival	594
	b. Growth, Hematology, Clinical Chemistry, and Urinalysis	600
	c. Carcass Characteristics	608
	d. Meat Composition from the Progeny of Clones and Comparators	609
D.	Conclusions from the ViaGen Dataset	614
	1. Study 1: Clones vs. Comparators	614
	a. Animal Health	614
	b. Food Safety	615
	2. Progeny of Clone Boars vs. Progeny of Comparator Boars	615
	a. Animal Health	615
	b. Food Safety	616
E.	Addendum	617
ViaGen Data Chart Interpretations		621
ViaGen Raw Data		695
Appendix G: Unpublished Data		857
A.	Perinatal Development in Cattle Clones (Node 2)	857
B.	Juvenile Development in Cattle Clones (Node 3)	859
C.	Reproductive Development and Function in Cattle Clones (Node 4)	865
D.	Post-pubertal Maturation in Cattle Clones (Node 5)	867
E.	Summary of Cloning Studies at University of Tennessee	868
	1. Developmental Node 1: Pregnancy and Parturition	868
	2. Developmental Node 2: Perinatal Period	869
	3. Developmental Node 3: Juvenile Period	869
	4. Developmental Node 4: Reproductive Development and Function	869
	5. Developmental Node 5: .Post-pubertal Maturation and Aging	870
F.	Perinatal Development in Swine Clones (Node 2)	870
G.	Conclusions for unpublished data	872
Appendix H: The Comprehensive Veterinary Examination		877
A.	Introduction to the Comprehensive Veterinary Examination	877
B.	The Importance of Species-Specific Standards	878
C.	How a Veterinarian Performs a Comprehensive Veterinary Examination	878
	1. Specific Considerations for Neonatal CVEs	880
	2. Specific Considerations for Juvenile CVEs	881
	3. Specific Considerations for Mature Animal CVEs	881
	4. Specific Consideration for Reproductive Stage Examinations	881
	a. Males	881
	b. Females	882
D.	Interpreting the Comprehensive Veterinary Examination for Animal Clones	883
E.	Parameters Evaluated in the Comprehensive Veterinary Exam for a Risk Assessment	883
Appendix I: Investigation on the Attributes of Cloned Bovine Products		895