Dr. Peter Hansen has been fascinated with dairy cattle since he was a young boy. Growing up, he spent time visiting his cousin’s small dairy farm in Ireland, helping work the dairy and breed cows. Hansen decided that he wanted to find a career path that could merge his interest in animals and science. Like many young animal enthusiasts, when Hansen began college at the University of Illinois, he believed that veterinary medicine was his future. However, in his first-class, Animal Science 101, Hansen discovered that he found the topics of animal genetics and reproduction far more interesting.
Today, Hansen is a Distinguished Professor in the UF/IFAS Department of Animal Sciences, where he conducts research in the fields of thermal biology and embryology, primarily focused on dairy cattle.
A dairy’s success is dependent upon their cows becoming pregnant each year and providing milk. Selecting which cows and bulls to breed can have a significant impact on the offspring’s milk production, health, and longevity. Genomics has helped producers be able to identify which cows carry the preferred genetic traits for high milk production. However, even if you know which cow is best, she can still only give birth to one calf a year. This means she would become old before you could significantly improve the genetic quality of your herd through breeding.
One solution for producers might be to use embryo transfer. The embryo transfer process allows producers to harvest oocytes, or eggs, from the best cow, and then transfer them to other cows in the herd. This means multiple cows could carry the genetic calves with the genes of the best cow. This process would theoretically allow a producer to improve the quality of their herd much more quickly.
There are two ways to make embryos. With superovulation, cows receive a stimulating hormone to grow multiple follicles rather than just one. This process might yield around 30 embryos a year, which is much more than just one. However, it is an expensive process and has diminishing returns. With time, cows become less responsive to the stimulating hormones. The second method is in vitro fertilization (IVF). With IVF you use ultrasound to see the follicles. Then extract out the eggs and fertilize them in vitro, or in a dish. The embryos grow in the dish for seven days and then are placed into recipient cows.
“The advantage of that (IVF) technique is that you can do it every two weeks, when she’s pregnant, or when she’s not even pubertal,” Hansen said. “So you can get a lot more embryos from a cow. But the embryos are abnormal. Not horribly abnormal, but they have a lower probability of establishing pregnancy than those embryos produced by superovulation.”
While embryo transfer is being utilized in elite dairy herds, the process is currently cost-prohibitive for smaller dairy farmers. One of Hansen’s research areas is to learn how to make embryo transfer a more viable option for dairy producers. Right now, one of the greatest disadvantages of embryo transfer, is that the rate of establishing pregnancy is only roughly the same as using artificial insemination (AI), which is much cheaper.
“Theoretically, the pregnancy rate to embryo transfer should be higher than a pregnancy rate to artificial insemination,” Hansen said. “With AI some cows don’t get pregnant because the semen is bad or the sperm get killed in the reproductive tract, or the oocyte is lost and doesn’t go into the oviduct or it dies in the first six days of pregnancy. So, all that gets bypassed with embryo transfer. I mean you put in a living, fertilized embryo. All that early pregnancy loss is eliminated, so you should get a lot higher pregnancy rate with embryo transfer, but you don’t, and we aren’t sure why.”
Hansen suspects some aspects of the technique need to be optimized. Or that the process of making the embryo through IVF alters its development, resulting in less ability to establish pregnancy.
Hansen and his graduate students are working to make in-vitro fertilization a more effective method of embryo transfer. They are working to identify what missing molecules produced by the cow’s uterus help the embryo grow. Hansen’s embryology lab is working on identifying these molecules so that they can add them to the IVF cultures to help improve the embryo’s pregnancy rate.
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