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Reseachers help preserve pedigree line
(April 26, 1999)
A two-week-old Shorthorn heifer at Smyth's Trinity Farm in Enfield is the latest poster-calf for the nation's dairy cattle breeding industry.
Sarah - whose mother Snowflake was a national champion of her breed but had to be euthanized last summer after breaking her leg - was literally salvaged by a team of UConn scientists who have pioneered state-of-the-art procedures for harvesting eggs from cow ovaries for in vitro production of embryos.
"This is an excellent example of genetic salvage from a terminally ill farm animal," says Xiangzhong (Jerry) Yang, associate professor and head of the Transgenic Animal Facility in the College of Agriculture and Natural Resources. "The mother was dying.
At stake was her line of genetics, which we have preserved for another generation."
Nationwide, millions of dollars are spent each year on breeding programs to improve the genetic pool of dairy livestock with the goal of reproducing animals highly valued for their production potential.
For example, the average milk production of most dairy herds in Connecticut is about 16,000 pounds per animal annually, notes Yang. "Yet there are cows that produce between 35,000 and 50,000 pounds a year," he adds. "The difference is in the genetic pedigree.
"Imagine if we could produce the same amount of milk with one-third of the animals we now have," Yang continues. "We could dramatically reduce the animal waste problem (which some environmentalists blame for temperature increases that have triggered the global warming crisis) and still meet consumption demand."
Cows are born with a lifetime supply of eggs in their ovaries, and Yang is a leading world expert in embryo transfer research. His lab at UConn's Transgenic Animal Facility is one of just two or three labs in the world that perform a complex breeding procedure known as transvaginal ultrasound-guided oocyte pickup, or OPU, for producing offspring from pre-pubertal heifers.
OPU uses ultrasonography to identify the follicles within an ovary. Each follicle contains fluid and an oocyte, or immature egg. A needle attached to a probe is used to aspirate the fluid and oocyte into a tube, which is returned to the lab for in vitro fertilization. The fertilized egg is then reintroduced into a cow for gestation.
In Sarah's case, Anne Smyth, the owner of the calf's mother Snowflake, was a student in the Department of Animal Science and familiar with Yang's bovine in vitro fertilization program. Smyth approached Yang for help after Snowflake, judged as 1996 All American Intermediate Heifer Calf at the Dairy Exposition in Wisconsin, the equivalent of the World Series of livestock shows, broke her right foreleg soon after giving birth to a healthy bull calf in the summer of 1998.
"I wanted to have a few more offspring from Snowflake to preserve her genetic line, especially a heifer calf," Smyth explained.
On June 24, 1998, Snowflake was euthanized and her ovaries immediately brought to Yang's laboratory where Yang's colleague, post-doctoral research scientist Maneesh Taneja, using OPU technology, removed 18 eggs from Snowflake's ovaries, eight of which were classified as viable.
The eight oocytes were cultured in a laboratory incubator, followed by in vitro fertilization using frozen semen from a valuable Shorthorn bull named Pacesetter, which was provided by the Smyths. Three viable embryos were produced seven days later and were implanted into three Holstein recipient cows provided by Fairvue Farm in Woodstock, Conn. One cow became pregnant.
On April 3, the recipient cow bearing the pregnancy from Snowflake's ova gave birth to a healthy heifer calf - Sarah.
Asked whether she wanted to enter her new calf in state and national competition, Smyth noted that Sarah "sure looks as though she has the genetic makeup of her mother. If I show her and she wins, her value will increase a lot." She adds, "It's like raising thoroughbred horses."
From Yang's perspective, there is a sufficiently large commercial market interested in using OPU technology in breeding programs for domestic livestock. Sarah's birth is the second time that he and Taneja have given nature a hand by collecting eggs from the ovaries of dead or dying valuable livestock and successfully using "test tube" baby technology to preserve the genetic line. Their first success came in October 1997, when an in vitro bull calf was born from eggs obtained from the ova of a high-producing Holstein dam.
"We have demonstrated our capability to reproduce animals," Yang says. "There is a tremendous market in the dairy industry for successfully reproducing highly valued animals. This, along with recent breakthroughs in cloning, could become a profitable business."