New Bison Calf at Bronx Zoo Produced Through Embryo Transfer

The Wildlife Conservation Society has announced the birth of the first genetically pure bison calf ever produced by embryo transfer through a program aimed to establish a breeding herd of non-introgressed bison (without cattle genes) for restoration projects and zoos. Using female bison from the American Prairie Reserve herd, a healthy calf was born this summer to a happy and protective mother.

From the Wildlife Conservation Society:

The Wildlife Conservation Society’s Bronx Zoo has announced the birth of the first ever genetically pure American bison calf produced by embryo transfer.

The success is the result of collaboration between Colorado State University, USDA-Animal and Plant Health Inspection Service, the American Prairie Reserve, and the Wildlife Conservation Society.

In the fall of 2011 WCS arranged for a group of female bison originating from the American Prairie Reserve to be sent to the CSU’s Animal Reproduction and Biotechnology Laboratory facility in Fort Collins, Colo. to serve as recipients for fertilized embryos from a herd of genetically pure bison managed by USDA-APHIS. Dr. Jennifer Barfield, a CSU reproductive physiologist, and her team collected the embryos non-surgically and implanted them into the surrogate bison.

An ultrasound exam performed two months after the embryo transfers confirmed that one animal was pregnant. “This science illustrates that we can engineer breeding of pure-bred bison so that their valuable genetics can be incorporated into other herds or used to create new herds,” said Dr. Barfield, CSU Assistant Professor. “We are able to produce bison that have pure genetics and are also free of any diseases that can afflict the bison population at Yellowstone.”

The pregnant bison and her herdmates were moved to the Bronx Zoo in early April and the calf was born on June 20. The mother, calf, and herd continue to do well and are maintained in a section of the zoo that is not open to the public. Although this group and the calf will not go on exhibit, zoo visitors can see American bison on the Bronx Zoo’s bison range.

A second round of embryo transfer will be attempted with the herd of surrogate females in the fall, with the goal of eventually establishing a breeding herd of genetically pure bison.

“The Bronx Zoo played an important historical role in the recovery of the American bison, and by establishing a pure herd, the zoo will be, in essence, returning to its roots,” said Dr. Pat Thomas, WCS Vice President/Bronx Zoo General Curator and Associate Director. “The offspring of these bison will be used in future restoration programs and to establish herds in other AZA-accredited zoos.”

The bison is an American conservation success story.  In the early 1900’s, the bison was on the verge of extinction – numbering less than 1,100 individuals after roaming North America in the tens of millions only a century earlier. In 1907 and 1913, the Bronx Zoo sent two herds of bison out west to re-establish the species. Today, bison number in the hundreds of thousands in the U.S. and are found in state and national parks, wildlife refuges, and on tribal and private lands.  However the vast majority of present-day bison have traces of domestic cattle genes, a reflection of past interbreeding efforts when western ranchers tried to create a hardier breed of cattle.


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