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  • Megan Silveira, associate editor

Fertility in the Future

Understanding and predicting fertility in bulls is helping achieve reproductive efficiency.

In the discussion of fertility, the cow often takes precedent. Francisco Peñagaricano, assistant professor of qualitative genetics at the University of Wisconsin, said the bull rather than the cow should be at the forefront of these conversations.

“A single bull will have a larger impact than a single cow on genomics,” Peñagaricano said during his presentation, “Genomic Discussion and Prediction of Bull Fertility,” at the 2021 Beef Improvement Federation (BIF) Research Symposium & Convention hosted June 22-25 in Des Moines, Iowa.

Peñagaricano reminded producers a cow typically can only produce one calf each breeding season, whereas a bull can sire numerous calves. A vast majority of beef producers share the goal of improving reproductive efficiency, so, Peñagaricano said, it’s important for members of the beef industry to understand fertility in bulls.

With past research on data of dairy bulls, Peñagaricano said genetic factors do explain part of the variation in bull fertility.

Francisco Peñagaricano described genomic prediction as a black-box tool and said it has great potential to be applied to the subject of fertility.

However, he explained, genes with the ability to influence fertility do so with miniscule effects. Often, it’s novel regions, genes or variants in genetic data that Peñagaricano finds have large nonadditive effects on the next generation of livestock. For this reason, pathways, rather than single genes, are often the primary targets of selection for fertility.

Homozygous bulls are also often seen to possess lower genetic diversity, Peñagaricano said, warning producers that homozygosity might be an important risk factor for bull fertility.

With all this in mind, Peñagaricano said, the next question producers have is, “Can fertility in a bull actually be predicted?” His answer: Yes.

“Genomic prediction works,” he said. “It is outstanding. There is no discussion.”

In fact, genomic prediction is so strong that for smaller breeds of cattle, Peñagaricano said, it will even be able to be used to produce across-country evaluations.

Peñagaricano described genomic prediction as a black-box tool and said it has great potential to be applied to the subject of fertility. With Peñagaricano’s research focusing on dairy bulls, he encouraged future research and evaluation to focus on calves from beef-on-dairy crosses to help researchers continue to better understand the fertility of beef bulls.

As technology continues to advance and producers push the industry forward, Peñagaricano said, research on both genomics and bull fertility will continue to be at the forefront of producers’ minds.

Eventually, the focus of the fertility conversation might start to naturally shift to center on the bulls rather than just the cows.

Find more coverage of the 2021 BIF Symposium in the Newsroom and on the Awards page at


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