How can one bull have such a big impact? A genetic mutation traced back to one of the most prolific bulls in history is thought to be responsible for an estimated 500,000 spontaneous abortions in Holstein cattle worldwide. Now that this mutation has been identified it can be tested for, allowing the problematic mutation to be avoided in future generations by using breeding technologies.

Image: Holstein cattle at the UC Davis Dairy Facility (Gregory Urquiaga/UC Davis)

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The potential of the genetic tools available to the modern producer continue to reveal themselves in new and powerful ways. Indeed, one recent study has discovered the gene responsible for reduced fertility that affects the modern Holstein population. A mutation was found in a gene called APAF1 (apoptosis peptide activating factor 1). If the APAF1 mutation is inherited from one parent, the offspring becomes a carrier. But when copies of the mutation are inherited from both parents, the combination is fatal.

This mutation has now been traced back to a single bull. The bull in question – Pawnee Farm Arlinda Chief – produced 16,000 daughters, 500,000 granddaughters, and more than 2 million great-granddaughters, as well as sons who were popular sires too. Chief’s popularity has led to his chromosomes accounting for almost 14% of the genome in the current Holstein population in the United States, and has consequently produced an estimated half a million spontaneous abortions. Luckily, the identification of the problem mutation now allows diagnostics tests to be used to avoid mating two APAF1 carriers, while still imparting the beneficial genetic contributions that led to Chief’s popularity.

Read the full story on the UC Davis website