The potential of embryo transfer in a German horse-breeding programme.

This research examines the impact of using embryo transfer and a more stringent selection process for mares on the genetic gains achieved in a German horse breeding programme.

Introduction

The paper investigates the use of embryo transfer (ET) and a more rigorous selection of mares in a German horse breeding programme to maximise genetic gain. In this programme, a simulation of 13500 foals generated each year was created using ZPLAN+, a software for the optimisation of breeding programmes.

Scenarios and Selection

Two different scenarios were created. In scenario I, selection was based solely on a mare performance test. The second scenario, scenario II, selection was more rigorous, including additional information from 20 competitions over two years. Based on these selection criteria, mares were chosen to use for ET. Some were also used for multiple ovulation and embryo transfer (MOET).

Variables and Variations

Several variables were tested, including the selection intensity and the number of foals produced from ET or MOET. Assumptions included that 250, 500, or 1000 mares were available for selection to yield 20, 50, 100 or 200 donor mares each year. It was also varied how many foals each donor mare could produce, from one to six per year, over 4 years.

Genetic Gain

The research found that with high intensity in selecting mares and a high reproduction rate, the yearly genetic gain could significantly increase. In scenario II, where additional information was used for selection, the accuracy of the selection index grew to 0.85. With optimal parameters (200 selected donor mares out of 1000 potential mares, and six foals produced per year), the genetic gain could almost double compared to the reference scenario.

Costs and Drawbacks

However, these gains come at a cost, both literally and genetically. The implementation of ET increases the cost of the breeding program and reduces genetic diversity. In the most extreme MOET scenario, the effective population size was reduced by 19% as compared to the reference scenario.

Conclusion

The paper concludes that the use of ET and MOET in horse breeding programs is only a practical and sensible option if the increased genetic gain leads to higher returns for breeders to offset the costs and diversity loss.