Boar semen biomarkers
predict litter size

pig litter

Pig business is big business. In 2012 alone, China, the world’s largest producer of pork, produced 50 million tons of the meat. Getting pigs to produce large litters reliably is of great economic importance in places like China, the United States and the European Union. In a recent study published in Molecular & Cellular Proteomics, researchers describe biomarkers on boar sperm that can predict the animal’s fertility.

Myung-Geol Pang at Chung-Ang University in South Korea led the MCP study. He says one challenge the pork industry faces is the reliance on “inefficient methods to evaluate semen quality that could directly affect litter size.” Pang explains that current semen analyses look at some quantitative aspects of the sperm, “but the sensitivity of such analyses remains a subject of debate.”

So Pang and his colleagues wanted to come up with a different way to determine boar semen quality. Pang notes that pigs are a good model system in biomedical research, so work in pigs could have applications in human fertility.

In particular, because Pang and colleagues wanted to find protein biomarkers that would predict litter size, the investigators undertook a proteomic analysis of boar semen. They collected semen from 18 stud boars at a Korean pig farm. Using methods like gel electrophoresis and mass spectrometry, Pang and colleagues analyzed all the proteins in the samples. They then matched their data to the number of pups sired by each stud boar.

Based on that information, the investigators grouped biomarkers that predicted whether a boar would sire a large number of pups (about 12) or a small number (10 or fewer). L-amino-acid oxidase, mitochondrial malate dehydrogenase 2 and calmodulin were among the proteins notably expressed in semen that gave large litters. Proteins such as Ras-related protein Rab-2A, spermadhesin AQN-3 and NADH dehydrogenase were abundant in semen that produced small litters. In total, the investigators found 11 protein biomarkers that predicted litter size. “These biomarkers may be particularly important in the animal industry for the prediction and selection of better litter sizes,” says Pang. “Also, we cannot ignore their possible application to humans.”

Pang says to further improve their analyses, they now need to do large-scale mining of the mRNA markers to make sure that the mRNA expression levels correlate with the expression levels of the protein biomarkers they found. He says, “We believe that this next study will provide valuable biomarkers of male fertility and contraception” that accurately predict fertility.

Rajendrani Mukhopadhyay Rajendrani Mukhopadhyay is the senior science writer and blogger for ASBMB. Follow her on Twitter, and read her ASBMB Today blog, Wild Types.