Methodological and Ideological OptionsRationalizing ex situ collection of reproductive materials for endangered livestock breed conservation
Introduction
Globally, commercial livestock production is dominated by a limited number of specialized breeds, displacing many local breeds, which are at risk of extinction (Hopkin 2007; Tisdell 2003). This concentration potentially forecloses future breeding options and the adaptability to changing market, and production environments (Hoffmann 2010). Improvements in ex situ storage of germplasm (cryoconserved semen, ova, embryos or any cell with reproductive potential), are a complementary (to in situ) approach for conserving genetic diversity between and within breeds and maintaining breed and trait restoration options open to countries (Delgado Bermejo et al. 2019). Due to their economic and socio-cultural significance, commercial livestock breeds are at the forefront of ex situ conservation efforts undertaken in many countries and regions in both public and privately funded collections (Leroy et al. 2019). While there has been considerable attention on the technical feasibility of storage and use of materials (Morrell and Mayer 2017), breed prioritization algorithms (Simianer et al. 2003) and to some extent the ethical and governance implications (Farhadinia et al. 2020), there has been less discussion about the need to rationalize collections, using criteria that might be expected to guide efficient investment decisions (Tisdell 2015). This entails clear articulation of the relevant cost-effectiveness criteria, including the configuration of national and international collections to avoid redundancy, and accounting for evolving in situ conditions.
Addressing this problem, De Oliveira Silva et al. (2018) explored mathematical optimization as an approach to illustrate how rationalization criteria applied at a European scale might entail fewer or even a single collection. Focussing mainly on variation in collection costs, the analysis did not account for specific national objectives and obvious institutional constraints that might drive ex situ priorities according to sub-national in situ breed risk status. To develop this idea with a specific national case study, this paper develops a stochastic chance-constrained linear programming (SCLP) model to rationalize collections under projected risks of in situ extinction. The model is a novel approach to rationalize collections by determining the optimal collection location, timing and quantity of material (semen doses). Using Spanish breed status data, the model introduces an exogenous decision constraint, an ‘acceptable level of risk’, allowing planners to determine national inter-temporal ex situ investment decisions using information on subnational in situ breed status and accounting for uncertainty within in situ populations.
This paper is structured as follows. Section 2 considers drivers of endangerment the current status of Spanish livestock breed conservation and stated policy objectives. Section 3 presents methods details the modelling approach to address policy, and outlines the data used in the analysis. Section 4 presents extinction risk scenarios and the cost-analysis results. Finally, Section 5 discusses results and policy implications and Section 6 offers conclusions.
Section snippets
Spanish conservation efforts
As in many countries, a combination of market and policy failures has inadvertently driven diversity out of Spanish agricultural production (Perea et al. 2018). Market failure implies that a limited number of genetic traits have typically been favoured by producers responding to market signals, leading to concentrated breeding effort focused on high performing breeds containing these traits (Tisdell 2003). The same signals tend not to reward traits associated with cultural or other non-market
Collection criteria
The analysis considers collection of doses of frozen semen, the most abundant material in gene banks, a dose being the unit used for a single insemination. Following collection of semen doses, cryopreservation involves dilution in so-called extenders (containing nutrients and protectants), packaging (typically in individually identified plastic straws of in 0.25- or 0.5-mL), cooling and freezing, and subsequent storage in liquid nitrogen, at −196 Celsius (Sieme and Oldenhof 2015).
Semen
Results
The results involve three parts; uncertainty analysis of the in situ data and projections, least cost collection strategies and allocation of genetic materials in the gene banks, and sensitivity analysis of “acceptable level of risk” versus total collection costs.
Discussion
The uncertainly analysis suggests worrying extinction risks for both CTC and EDG scenarios. However, it suggests that cost-effective planning of future collections means extinction risks can be minimized by using existing local gene banks in coordinated collection efforts, including a national backup collection. The analysis shows how costs are sensitive to in situ projections and the “acceptable level of risk”, a decision constraint we introduce to inform future ex situ collections investments.
Conclusion
The evolution of cryoconservation methods is increasing the options for ex situ conservation as a complement to in situ efforts. The overall status of endangered livestock breeds can be enhanced by rationalization to avoid redundancy in ex situ resources, and systematic assessment of acceptable in situ extinction risks.
This country case study is an example of a modelling framework that can be replicated in other situations and regions with different breeding and conservation objectives. The
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
We acknowledge the participating institutions that provided cost data for this work and to the Spanish Ministry of Agriculture, Fisheries and Food. This work received funding from the European Union's Horizon 2020 Research and Innovation Programme under the grant agreement n° 677353 for the IMAGE project (Innovative Management of Animal Genetic Resources). Rafael Silva acknowledges The University of Edinburgh's Data-Driven Innovation Chancellors fellowship.
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