Breeding bulls: Genetic test highlights infertility
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- This proud Simmental – going by the name of Steinadler (Golden Eagle) – bears all the magnificent qualities of an ideal breeding bull. Animal geneticists in Munich have developed a new kind of genetic test that can assist in the selection of fertile breeding bulls. Source: Bayern-Genetik GmbH
20.01.2014 -
The majority of Simmental cattle appear the very picture of strength and good health. But there are some that carry a tiny alteration in the genetic material that lowers the possibility of producing offspring to almost zero. Researchers in Bavaria have found a genetic defect on chromosome 19 that affects the quality of sperm to such an extent that the bull becomes infertile. The researchers at the Technical University of Munich used the most up-to-date sequencing techniques to detect the mutation. Using a genetic check, it will now be possible to determine which cattle are suitable as breeding animals. The work has been published in PLOS Genetics (2014, online) The BMBF has funded the work from 2009 to 2014 as part of the SYNBREED research cluster.
Simmental cattle originate from the Alpine region. Today, this robust breed is at home on all continents – it is estimated that there are about 40 million of the animals worldwide. In Germany, there are around one million Simmental dairy cows. “Their genomes can be traced back to just a few ancestors, so-called key ancestors,” says Ruedi Fries, head of the Department of Animal Breeding at the Technical University of Munich (TUM). “Using artificial insemination, male breeding animals can produce over a hundred thousand offspring.”
Mutation on chromosome 19 causes infertility
| SYNBREED research network |
The BMBF is investing up to €12 million in the research network SYNBREED up to 2015. Here, the partners are researching advanced methods for animal and plant breeding. The network is coordinated by the Technical University of Munich.More information can be found here. |
Nevertheless, this approach does carry some risks: If there is an undetected genetic defect in the genome of the cattle, this characteristic will be propagated in later generations. Scientists at the TUM have now discovered that a mutation in the gene TMEM95 on the bovine chromosome 19 renders the bulls almost infertile – not even two percent of all inseminations are ultimately successful. “The animals otherwise appear entirely healthy and ordinary,” says Hubert Pausch, first author of the study. “The characteristic will only develop, however, when cows inherit the mutation from both the father and mother, i.e. homozygous for the defective gene. Only in this case should the animals be excluded from breeding.” Since August 2012, all breeding bulls are examined with a genetic test as a matter of routine.
Protein molecule on sperm surface
The research has been funded by the Federal Ministry of Education and Research as part of the SYNBREED agricultural research cluster. In the study, the scientists compared the genome of 40 sub-fertile cattle with 8,000 normal fertile breeding bulls. This led them to the discovery that the genetic defect can be traced back to a Simmental ancestor born in 1966. The TMEM95 gene codes for a protein found on the surface of the sperm heads. This protein mediates the binding between the sperm cell and the egg cell. If it is lacking, fertilisation cannot take place. “Our work provides evidence that genetic defects in TMEM95 could also lead to infertility in men,” explains Pausch. In the study of the sperm of infertile breeding bulls, the TUM scientists worked together with Sabine Kölle and Matthias Trottmann from the Grosshadern clinic site at the LMU Munich. Trottmann offers guidance to couples wishing to conceive.
Genetic analyses for improved animal health
Since 2009, the genomes of cattle are systematically examined. Unlike in humans, relatively few gene loci can explain a large proportion of characteristics. “This allows the genetic profile of breeding bulls to be characterised extremely precisely. Individual weaknesses can then be taken into account in breeding,” says Pausch. Fries adds: “Genetic analyses show the desirable features but also the diseases that the animals will inherit. This brings about improvements in yield and quality, and also encourages animal health by locating disease-causing gene variants, ensuring that they are not passed on.” In 2012, the SYNBREED researchers also demonstrated the existence of a hereditary pattern that results in Simmental offspring with brown fur rings around the eyes (more...).
