Holstein genes hold clues to cause of twinning

Narrowing down the locations of genes that cause twin births in Holstein cattle is possible through use of DNA sequencing technology, according to a report published online in March, 2010 by the Journal of Animal Science. Researchers at the University of Wisconsin and Iowa State University analyzed gene markers and associations between genes to refine the locations of three genes responsible for twinning (Bierman et al. 2010).

Twinning in cattle is a problem for the dairy and beef industries. Cows pregnant with twins are more likely to have infertile young, difficulty giving birth, reduced milk production, or longer return-to-estrus periods. Complications due to twins have been shown to result in a $110 loss per cow in the dairy industry. “Milk is their product. Anything that has a negative impact on the cow is a problem,” said Dr. Brian Kirkpatrick, co-author of the paper and professor at the University of Wisconsin – Madison. Locating the genetic markers for twinning will help cattle breeders select cows that are less likely to have twins.

The researchers used a gene-mapping system called linkage disequilibrium analysis, which determines the associations between traits at different locations on a chromosome, specifically on bovine chromosome 14 in this report. The data from the linkage disequilibrium tests agreed with reports from previous studies using similar methods and cattle populations. The team also reanalyzed significant gene markers from previous studies. By comparing their data with existing data, they determined that three genes that lead to twinning are located in a 21-megabase region on Holstein chromosome number 14. A fourth gene is probably nearby on chromosome 14, and a fifth may lie just outside this 21-megabase region. The true number of genes that cause twinning is still unknown. “There are a number of different genes that lead to twinning,” said Kirkpatrick. “This study gives us better information on the genetic markers.”

Kirkpatrick indicated that future results could be more definite as scientists amass a larger dataset. He said gene-mapping technology to improve the data is out there, and once the data are compiled, scientists can compare studies and better pinpoint the locations of specific genes. Until then, managers in the dairy and beef industries can use broader gene maps to determine which cattle have a greater propensity for producing twins.

While most Holstein breeders want to select against twinning in their herds, some would like to use gene markers to select cattle likely to produce twins. Kirkpatrick said the production of twin calves is valued among some breeders in the beef industry.

The report by Bierman et al. is entitled “Fine-mapping quantitative trait loci for twinning rate on BTA14 in North American Holsteins.” It was first published online by the Journal of Animals Science in March, 2010. Read it in full at journalofanimalscience.org.

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