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October 28, 2014
President, Genetic Computation, Ltd.
Retired Professor, Dalhousie University (Canada)
Founding Director, Marine Gene Probe Laboratory, Dalhousie University
Former President, International Association for Aquaculture Genetics
Former Director, Aquaculture Genetic Network in Asia (IDRC, Canada)
Dr. Roger Doyle (email@example.com) reports:
In this note, I will briefly describe the current status of the CP Food’s broodstock, as I understand it. I shall also try to eliminate some misunderstandings concerning the cause of the inbreeding that may be increasing production losses from EMS, other diseases and environmental stressors.
1) Firstly, the source of the inbreeding is not CP or any other large breeding company or supplier of postlarvae (PLs). In the case of CP, I have helped guide the Penaeus vannamei and P. monodon broodstock development programs from inception and can state from my own knowledge and intention that the programs are not based on deliberate inbreeding. Just the opposite, they are based on retaining as much diversity as possible and minimizing inbreeding. Here are some facts about CP’s broodstock:
2) CP’s broodstock has not yet, after more than twelve generations, reached an inbreeding level of 5%.
3) In response to EMS, CP has been selecting hard for EMS tolerance and does not select solely for growth. It also selects for survival and other important farm/hatchery performance traits. The breeding design puts 50% weight on maintaining genetic diversity and minimizing the accumulation of inbreeding and 50% on all other traits put together.
4) Survival, growth rate, disease resistance and fecundity have all been increasing generation after generation in the CP lines. Feed and other resources are not limiting in the farming systems recommended by CP, and the increasing adaptation to the farm environment has, so far, benefitted all production traits. There is no trade-off so far.
5) The exact values of production traits are proprietary information, but CP will, on request, provide arbitrarily scaled data so that the time trends and positive genetic correlation among traits can be verified in reference to the pedigree. CP will also provide, on request, summary statistics derived from the pedigrees, like effective population size, founder equivalent diversity and other technical measures of inbreeding and genetic diversity in its stocks.
6) CP sells PLs to farmers for growout, not for use as breeders. Its PLs are produced in a way (the “breeder lock”) that guarantees that their inbreeding is zero – yes, zero – in the farm ponds where they are grown. The breeder lock is the universal practice of large breeding companies and is recommended by Worldfish, the Food and Agriculture Organization of the United Nations and other organizations. The benefit to the farmers using locked stocks is that their animals have zero inbreeding when they meet the challenge of the environment.
7) The widespread inbreeding at the farm level that is amplifying the EMS crisis is caused by small hatcheries that breed PLs obtained directly or indirectly from large broodstock companies such as CP.
8) There is no technical mechanism that a large breeding company can use to prevent inbreeding at small hatcheries that breed its PLs. The inbreeding generated by small hatcheries is inherent in their smallness and will occur with whatever broodstock they use. Large companies cannot solve the problems created by small hatcheries. No doubt they wish they could because an epidemic spreads to all producers and ruins the environment for everyone.
9) As I have emphasized in recent lectures and publications, the cause of the inbreeding crisis is that 70% or more of farmed PLs come from small hatcheries that cannot avoid inbreeding. I have also pointed to some current national and international policies – and lack thereof – that may be making this percentage grow larger and the consequences worse. A number of general, policy-level solutions could be considered, and I would love to see them discussed more widely.
Source: Email to Shrimp News International. Subject: Genetic Characteristics of CPF Broodstock in Thailand. Roger Doyle. October 28, 2014.
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