PULLMAN, Wash. — For 30 years, dairy producers around the world have watched milk production soar while the fertility of their herds has plummeted.
It’s a multi-billion-dollar-a year problem for the U.S. dairy industry alone, according to the National Dairy Herd Improvement Association.
“They wanted milk, so that’s what breeding programs were selecting for,” said Matt Garcia, a post-doctoral associate in Washington State University’s School of Molecular Biosciences. “Dairy producers have been losing money because they have been forced to spend a lot on getting their cows pregnant and culling cows that were not getting pregnant, thus not calving and producing milk.
Reproduction is a lowly heritable trait and difficult to improve with traditional methods of selection.
“Between zero and 10 percent of differences we see in reproductive ability is attributable to genetics,” said Charles Gaskins, a geneticist and chair of WSU’s animal sciences department. “The rest is attributable to environment. Environment includes many things that we can’t directly identify, such as sub-clinical infection, nutrition and microclimate.”
As it turns out, it’s not as much a matter of cows looking for love in all the wrong places as a genetic mutation, according to Garcia, who discovered a cause of the problem while earning a doctorate in WSU’s animal sciences department under the direction of Zhihua Jiang, assistant professor of animal sciences.
“We had some idea of specific genes that might be affecting this trait based on other traits they appear to be associated with,” Garcia said. “We wanted to see if there were any mutations that might be coding for high or low fertility. After we scanned through the genes, we wanted to look at the whole genome because we had a very fertile group of cows and a group with very low fertility.”
Garcia did a complete genome scan of the DNA of the 60 most fertile and 60 lowest fertility cows from a population of 1,500 semen samples provided by the USDA Agricultural Research Service Animal Improvement Programs Laboratory in Beltsville, Md.
“We wanted to see what the difference was across the whole genome between those two groups,” Garcia said. “We found a significant candidate gene, the Calpistatin or CAST gene, and four regions in the bovine genome that could potentially be associated with increased fertility.”
The CAST gene is typically associated with meat tenderness. Further research found that the CAST gene is expressed in reproductive tissues, such as the ovaries and testes.
Jiang, Garcia and Washington State University have applied for a patent on the finding, which someday may help dairy producers use genetic markers to select for lowly heritable traits, such as reproduction. “If we can select for these mutations, we could dramatically increase fertility.”
He said the research could possibly benefit humans.
“We looked through human data in real detail,” Garcia said. “The region of mutation is present in humans, and the human genome project had not yet quantified this region on the CAST gene.
“If we can identify those markers within people, we can improve the success of in vitro fertilization procedures,” Garcia said. “Every person has different physiology and different genetic background. If we can treat the them specifically, we can probably increase in vitro fertilization results.”
The research was funded in part by WSU’s Agricultural Research Center.
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