Breeding for bigger cattle may come with hidden fertility trade-offs

A University of Queensland analysis of genetic data from northern Australian cattle has identified key regions of the genome that influence traits like fertility, growth and body condition, sometimes all at the same time.

Queensland Alliance for Agriculture and Food Innovation researcher Dr Mehrnush Forutan said the study helps explain why some cattle grow faster, reach puberty earlier and maintain better body condition than others. 

“We used sequence, gene expression and performance records from 28,000 multi-breed cattle,” Dr Forutan said. 

“Our goal was to understand how traits like height, weight, body condition score and puberty are genetically connected.”

The team found that some genetic variants create clear trade-offs.

“In some cases, the same variant that increases height is associated with delayed puberty and we also see the reverse, where variants linked to earlier puberty can reduce height.”

-Dr Forutan

Dr Forutan said trade-offs can make it difficult to balance breeding objectives, especially because fertility is typically harder to improve through selection.

“Fertility has lower heritability than growth traits, so progress can be slower,” she said. 

“Historically, strong selection for growth and size can also make it harder to pinpoint the causal variants that specifically affect fertility.”

Despite the challenges, Dr Forutan said the research highlights new opportunities to improve fertility without sacrificing performance.

“Importantly, several of the fertility variants we identified are already represented on commercial SNP genotyping panels,” she said. 

“Breeders can start using this information within existing genomic selection programs to better manage trade-offs.”

The team is now investigating whether AI can further improve the discovery of causal variants and their impacts across multiple traits.

“The ambition is to identify the variants that truly drive economically important traits and quantify their trade-offs more precisely,” Dr Forutan said. 

“Ultimately, this is about selecting animals able to get in-calf earlier and perform well rather than improving one trait at the expense of another.”

The research was published in Genetics Selection Evolution.

Collaboration and acknowledgements