“Phenotypes for bull fertility may be laboratory measurements centered around sperm quality, breeding soundness exams and scrotal circumference, but these are really indicator traits, and the ideal phenotype is a sire conception rate,” said Francisco Peсagaricano, Ph.D., University of Wisconsin assistant professor of quantitative genetics.
Peсagaricano gave his presentation, titled “Genomic Dissection and Prediction of Bull Fertility,” during the Beef Improvement Federation (BIF) Symposium June 23 in Des Moines, IA.
Peсagaricano discussed his study of predicting bull fertility, research findings and opportunities for bull fertility selection.
A study of bull fertility
Peсagaricano’s research focused on bull fertility, whether genetics influence bull fertility, relevance of non-additive effects, looking for major causal variants of bull fertility and, lastly, examining models for bull fertility prediction.
According to Peсagaricano, fertility is an extremely important economic trait, and genetic prediction of bull fertility is nonexistent in most genetic evaluations. Fertility predictions usually focus on the female, while bull fertility predictions have received less attention. The research centers on using sire conception rate with the records adjusted for variables related to cow fertility like lactation, age of the cow and days in milk.
“The sire conception rate was normally distributed with more than 10 percent difference in conception rate from high fertility bulls to low fertility bulls, even though all passed semen quality tests and adjusting for cow fertility effects,” Peсagaricano explained.
Research findings
After conducting research supporting typical polygenic control of sire conception rate in both Holstein and Jersey populations, Manhattan plots showing genetic variation explained by different regions across the genome looked like a typical polygenic trait, with many genes/regions across the genome having small effects on the trait, and no region explaining more than 1 percent of the genotypic variance.
While the peaks/regions were distinctly different in the Holstein and Jersey population, many of the pathways/biological mechanisms affected by those genes were common between the two populations, suggesting evidence that pathways for molecular mechanisms, rather than by single genes, are primary targets of selection. These pathways include spermatogenesis, sperm motility, fertilization and testis development.
“My colleagues and I asked if we could use SNPs (single nucleotide polymorphisms) to predict bull fertility. We found a predictive correlation of 0.34 and prediction accuracy of 0.62,” Peсagaricano summarized.
Peсagaricano’s presentation offers paths toward selecting for improved bull fertility or at minimum, screening for subfertile bulls. The selection tools for beef bull fertility don’t exist outside of simply passing a bull soundness exam or minimum semen standards. The research from Peсagaricano is promising for the genetic improvement of beef bull fertility.
To watch Peсagaricano’s full presentation, visit https://youtu.be/v_lOz62E0fI. For more information about this year’s symposium and the BIF, including additional presentations and award winners, visit BIFSymposium.com. — BIF
