To clone or not to clone – is that really the question?
With the advent of cloning polo ponies 15 years ago, the jury was out for some time on whether or not it would prove successful – and the debate continues.
“When Adolfo [Cambiaso] cloned his best horses he had a lot of success. But the reality is that not all horses have the predisposition to produce clones,” said Dr Scott Swerdlin, founder of Palm Beach Equine Clinic [PBEC] in Wellington, Florida. All-time great polo player Cambiaso famously won the Argentine Open Polo Championship – the most competitive tournament worldwide – in 2017, with six clones from one of his leading polo ponies – a mare – Dolfina Cuartatero, in his string.
“If Adolfo Cambiaso says clones are amazing and he rode six clones and he won the cup, that’s a really good marketing campaign,” said PBEC reproduction specialist Dr Justin McNaughten. “But what I say when I talk to breeders, is that you never know what you’re going to get. And I think there are some very good mares and there’s some very good bloodlines. So there are some horses that do a very good job of producing offspring for their sport. But I also think there are some very athletic, equine athletes that do not do a good job of becoming producers. And with cloning there is also the nature versus nurture aspect – you have to look at the whole picture.”
Prior to cloning, embryo transfer was the innovative method of reproducing from mares who were still actively competing. An embryo from an impregnated mare is extracted and relocated in a surrogate mare for the rest of the gestation period. But just as life evolves, so too does the science on reproduction. Being able to have a foal from a sport horse that is still in its prime, is highly desirable and PBEC are offering another approach to the solution.
Intracytoplasmic sperm injection or ICSI has been around since 1996. It is not cloning nor is it embryo transfer, but it does allow reproduction without interruption of a sport horse’s career. It is a service offered by PBEC where eggs are removed in a clinical setting from the mare in Wellington and sent on to University of California, Davis for the next stage where a single sperm is all that is required to fertilize the egg and produce an embryo.
“They grow the embryo for five days,” said Dr Swerdlin. “And then they can either freeze it or put it in a receptor mare. You get a much better result than when we try to harvest an embryo from a mare’s uterus.”
Early transfer success rate with ICSI was low at 35 percent. “That’s not very good for the matter of work, you have to put in,” said Dr Swerdlin. They discovered that this was a problem with the freezing process so they went back to the drawing board and came up with a procedure where they could go into the embryo itself and remove the cytoplasm – the water out of the embryo – and then freeze it. “When you have less water, it has less crystalline. ICSI embryo transfer pregnancy rate was up to 70 percent,” Dr Swerdlin said. At that stage some frozen embryos were created here in Wellington from the Valiente [polo operation] and Adolfo Cambiaso’s mares and sent to La Dolfina in Argentina. “That was a nice way to be successful,” Dr Swerdlin said.
Now ICSI pregnancies are up to 80 percent. An avid polo player, Dr Swerdlin has applied ICSI to some of his own string and he has used some prime genetic material in the process. “For stallions with limited semen reserves, there wasn’t much that could be done [in the past],” he explained. “However, ICSI has become an invaluable tool for preserving sperm from deceased stallions or stallions with limited semen availability as the procedure uses less sperm to fertilize an egg.”
Frozen semen from stallions that have died is priceless. Being able to use just one sperm in the fertilization process – as opposed to the several straws required in embryo transfer – is a game changer. Dr Swerdlin saw the potential in this aspect of ICSI and has two colts on the ground out of his favorite mare Dolfino Foxygen and sired by Cambiaso’s famed, but no longer living, stallion Dolfina Boeing. “I’ve got the most amazing two stallions in the world,” said Dr Swerdlin of his new protégés. “The foals are beautiful and I hope I’m still playing when they are ready to play.”
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