By: Katherine Unger Baillie | Kbaillie@Upenn.Edu Assisted reproduction has become an invaluable technique for horse owners hoping to pass on to another generation the characteristics of cherished and successful animals. But for decades, one of the most common methods used in assisted reproduction in humans and other animals—standard in vitro fertilization (IVF)—has been stubbornly difficult to achieve. “It’s a frustrating thing,” says Katrin Hinrichs, professor of reproduction at the University of Pennsylvania School of Veterinary Medicine, who, alongside her other research programs, has tried for more than three decades to tackle conventional equine IVF, in essence, convincing a sperm to fertilize an egg in a Petri dish. “When we put horse sperm with eggs, they…