Jan. 9, 2014 The Fleckvieh is a breed of cattle that originated in the Alpine region. A robust animal, it is now found on every continent, with an estimated worldwide population of around 40 million.

In Germany, there are approximately 1 million Fleckvieh dairy cows: "Their genomes can be traced back to a small number of key ancestors," explains Prof. Ruedi Fries, Chair of Animal Breeding at TUM. "With artificial insemination, male breeding animals can produce more than one hundred thousand offspring."

Infertility caused by a single gene

This practice is fraught with risk, however: If the genetic make-up of any animal contains an unidentified defect, this characteristic will be passed on to future generations. TUM researchers have now discovered that a mutation in the TMEM95 gene on cattle chromosome 19 makes bulls effectively infertile, with a success rate for insemination of less than 2 percent.

"Otherwise, the animals are perfectly healthy and normal," points out Dr. Hubert Pausch, lead author of the study. "The characteristic only manifests itself if bulls inherit the mutation from both the male and female side, i.e. they are homozygous for the defective gene. It is only in this case that the animals should be excluded from breeding." Routine genetic testing for all breeding bulls has been underway since August 2012.

Findings of interest for human medicine

As part of their study, the researchers compared the genome of 40 subfertile animals with 8,000 breeding bulls with normal fertility levels. They discovered that the genetic defect can be traced back to one Fleckvieh animal born in 1966.

The TMEM95 gene encodes a protein on the surface of the sperm heads. The protein probably mediates the binding process between the sperm and egg cells. If it is missing, fertilization will not occur.

"Our findings indicate that genetic defects in TMEM95 could also cause infertility in men," elaborates Pausch. During their investigation of the sperm of infertile breeding bulls, the TUM scientists collaborated with Prof. Sabine Klle and Dr. Matthias Trottmann from Munich's Ludwig Maximilian University. Trottmann helps couples with infertility problems.

Genetic analysis for healthier animals

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Genetic testing to produce more offspring