My name is Diane Wray-Cahen. I am a science advisor for animal biotechnologies at the U.S. Department of Agriculture. I am an animal scientist and for my PhD research, I studied the metabolic effects of growth hormone (somatotropin) in pigs. I have been following this conference with interest as an observer.

This is in response to Tim Schwab's Message nr. 88. The focus of my comment is on the biology of growth hormone, rather than transgenic fish. Some of Tim Schwab's comments seem to imply that the effects of growth hormone are uncertain and there has been insufficient research to determine its effects. This is definitely not the case. 

The effects of elevated blood levels of growth hormone, whether due to gene engineering or exogenous administration, are well established and are not in dispute. Quite simply, in animals fed adequate nutrition, elevated growth hormone results in enhanced growth rates and improved feed efficiency or feed conversion rates (reference 1). The effect is dose-dependent.

This is extremely well documented in a large number of species, including fish. In fact, trout were used to determine the efficacy of some of the recombinant porcine growth hormone that we used in our studies in the 1980s. This is not a new technology and growth hormone was one of the first genes introduced into mice (2), livestock (3), and fish (4) in the 1980s. Augmentation of the growth hormone/insulin-like growth factor (IGF) axis was a target of many early genetic engineering efforts, for example with pigs (3, 5), precisely because of the well-documented effects of growth hormone on animal growth and feed conversion rates and the impact this could have on animal production.

The AquaAdvantage Salmon is not the only GE fish with a gene for growth hormone. For example, a highly respected research group in China at the Institute of Hydrobiology, Chinese Academy of Sciences (http://english.ihb.cas.cn/rh/rd/center3/201204/t20120409_83602.html) has a GE carp with a growth hormone gene (6). Research demonstrating that inserting a gene for growth hormone (as well as giving exogenous growth hormone) results in faster growing fish with enhanced feed conversion rates is not limited to studies done by Aqua Bounty nor is it limited to salmon. Thirty years of research drawing the same conclusions is not "speculation", but demonstrates an excellent body of evidence, at least in terms of animal growth and efficiency.

Diane Wray-Cahen, Ph.D.
Science Advisor for Animal Biotechnologies
New Technologies and Production Methods Division
Office of Agreements and Scientific Affairs, room 5949
Foreign Agricultural Service, USDA
1400 Independence Ave. SW, Rm 5949-S
Washington, DC 20250
USA 
tel: (202) 690-3324; fax (202) 690-3316
email: diane.wray-cahen (at) fas.usda.gov

References:
(1) Etherton TD. 2004. Somatotropic function: the somatomedin hypothesis revisited. J Anim Sci. 82 E-Suppl:E239-244. 
(2) Palmiter RD, Norstedt G, Gelinas RE, Hammer RE, Brinster RL. 1983. Metallothionein-human GH fusion genes stimulate growth of mice. Science. Nov 18;222(4625):809-14.
(3) Hammer RE, Pursel VG, Rexroad CE Jr, Wall RJ, Bolt DJ, Ebert KM, Palmiter RD, Brinster RL. 1985. Production of transgenic rabbits, sheep and pigs by microinjection. Nature. Jun 20-26;315(6021):680-3. 
(4) Zhu Z, Li G, He L, Chen S. Novel gene transfer into the fertilized eggs of goldfish (Carassius auratus L. 1758). Z Angew Ichthyol 1985; 1:31-4. 
(5) Pursel VG, Bolt DJ, Miller KF, Pinkert CA, Hammer RE, Palmiter RD, Brinster RL. 1990. Expression and performance in transgenic pigs. J Reprod Fertil Suppl. 40:235-45.
(6) Wu G, Sun Y, Zhu Z.  2003. Growth hormone gene transfer in common carp. Aquat. Living Resour. 16: 416-420.

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