Males obviously cannot be bred for a higher fertility

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Dummerstorf Scientists on the Trail of an Exceptional Scientific Phenomenon

Infertility is a relevant medical problem worldwide. Previous studies on the causes of male infertility are usually limited to the analysis of individual genetic defects. Molecular biologists and biochemists at the Leibniz Institute for Farm Animal Biology in Dummerstorf (FBN) have investigated a scientific question that has hardly or not at all been asked: are highly fertile males bred "automatically" when highly fertile females are selected? An affirmation of this question, which would solve many fertility problems in livestock husbandry, has not yet been given.

Research on a mouse model, which has been underway in Dummerstorf since 2013, has clearly shown that male animals cannot be adapted to this typical female breeding characteristic. The studies, which are funded by the German Research Foundation (DFG) with around 250 000 euros, are now to be continued in a larger research project. The findings are also of great interest to human medicine and were published last November in two prestigious English scientific journals*.

Time-lapse research on the mouse model
When breeding for certain physiological traits, e. g. female animals with a high body height and weight or a changed coat colour, male animals of this population also adopt the desired traits. Dr. Joachim M. Weitzel from the Institute of Reproductive Biology at the FBN said:"We were now concerned with the question of what happens when animals are selected for large litters and thus for high fertility. This is a primarily female selection criterion and has no significant consequences in male offspring. In contrast to female animals, male animals show a normal but no increased fertility in breeding. So far only females can be bred for high litter sizes."

The internationally renowned Dummerstorf mouse lines served as a basis for the molecular biological and hormonal analyses of male animals, especially on the basis of modern gene expression analyses. These are the only ones worldwide that have already been bred for increased fertility. The mouse of the Dummerstorf fertility line gives birth to an average of 20 offspring per litter, up to four times a year. Compared to a normal control line, these mice have almost doubled not only the number of offspring, but also the total birth weight of a litter.
“We were able to work in two ways at the same time,"Weitzel continued.” On the one hand, our mouse lines have been selected for the characteristic of high fertility for 180 generations, and on the other hand, mice are particularly suitable for such complex scientific questions due to their rapid reproduction and thus extremely short generation cycles”.

Research on male fertility continues
The Dummerstorf scientists were also able to show that two mouse lines selected for high fertility have developed different strategies for this task that are of concrete importance for pig breeding. Such data are also interesting with regard to the biodiversity of animal populations, since the same phenotypic characteristic, in this case high fertility, can obviously be implemented in different molecular pathways.
The work took place in the laboratory of the Department of Biochemistry at the Institute for Reproductive Biology of the FBN in cooperation with the Institute for Genetics and Biometry as well as the service group Model Animal Laboratory and the University Medicine Rostock.

“As part of a larger project, the investigations can now be continued and the experience gained so far can be deepened”, the scientist announced. “We suspect that genes and signalling pathways whose alteration is accompanied by a strong increase in fertility also play a role in reduced fertility. Thus, we hope that this project may provide an important basis for new insights into the treatment of male infertility”.

*Current scientific publications
„BMC Genomics“ - November 2017
Selection for female traits of high fertility affects male reproductive performance and alters the testicular transcriptional profile;
doi: 10.1186/s12864-017-4288-z

„Reproduction“ - November 2017
Testicular transcriptional signatures associated with high-fertility
doi: 10.1530/REP-17-0392 (not yet online)

Photos: FBN
Portrait: PD Dr. Joachim Weitzel
In the service of science - the Dummerstorf Mice

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Leibniz Institute for Farm Animal Biology (FBN)
Wilhelm-Stahl-Allee 2, 18196 Dummerstorf
Director: Prof. Dr. Klaus Wimmers
T +49 38208-68 600
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Institute of Reproductive Biology
Head: PD Dr. Jens Vanselow
PD Dr. Joachim Weitzel

T +49 38208-68 788
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Scientific Organisation: Dr. Norbert K. Borowy
Wilhelm-Stahl-Allee 2, 18196 Dummerstorf
T +49 38208-68 605
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