Why thoroughbred horse semen is the world's most expensive liquid

• Depending on the stallion, horse semen is one of the most expensive liquids on the planet.
• A gallon of gold-medal-winning Big Star's semen is worth $4.7 million.
• Wealthy investors are willing to pay high prices for a proven winner's semen.
• Visit Business Insider's homepage for more stories.

Following is a transcript of the video.

Narrator: Depending on the stallion, horse semen is one of the most expensive liquids on the planet.

Matson: So, we collected about 80 mils, and this is gonna be worth in excess of $100,000.

Narrator: That means that a gallon of this horse's semen is worth $4.7 million. And that's nowhere near the most expensive. Once it's collected, horse semen can be separated and sold in small tubes called straws.

Matson: One of these straws is worth about $1,200. We're putting about 150 million to 200 million sperm cells in each individual straw. Big Star's produced about 60 or 70 of them here.

Narrator: Super-fertile stallions like Big Star can ejaculate once a day. Theoretically, this means he could produce over $20 million worth of semen during an eight-month stud season. And if a stallion's semen is high quality, it can be frozen in straws for future use.

Matson: So, in this room is the heart of really Stallion AI Services. This room's built like actually a nuclear bunker in here. This is where all the semen is now kept. We've got hundreds and hundreds of thousands of straws in here. We've got over 1,200 different stallions. So, in here, stored at minus 196 degrees, is hundreds of millions of dollars' worth of semen ready to be used to inseminate mares.

Narrator: In the horse-breeding world, genetics is king. Wealthy investors are willing to pay high prices for proven winners' semen, hoping that the resulting foal provides a large return on investment.

Matson: Big Star is one of the most prolific show jumpers of all time. He's a double-gold-medal-winning stallion, which, there's very few of them out there. He's got the perfect genetics, really, to go on to show jumping. So you mix that with another genetic line on the female side and cross those two together. You can pay $1,200 for a single straw, you can have a foal, and maybe three or four years later, you can sell that foal for sometimes $100,000. In Big Star's case, he's hit those bells. He had the highest-price foal in the UK, and that sold for in excess of $100,000.

Narrator: Even though most stud farms offer guarantees on producing a live foal, commercial and competitive success is still a gamble, even with strong genetics. In fact, the bloodline of all stallion horses is closer than you might think. According to an international team of scientists who studied the Y chromosomes of 52 horses from 21 breeds, practically all modern horses descended from just a few original stallions, from carriage horses hauling tourists in the streets right through to champion racehorses like Galileo, the world's most expensive sire. Even more surprisingly, 95% of all thoroughbred racehorses, like him, can be traced back to just a handful of ancestors, who are all linked to one single superstud: the Darley Arabian, born in 1700. But the value of thoroughbred semen is a little harder to quantify, since breeding must occur naturally for racehorses.

Matson: In the sport-horse world, we're very lucky. We can use artificial insemination to breed our mares with, as opposed to the thoroughbred world, everything's got to be done naturally. They've got to literally cover the mare naturally. Their concern with their gene pool, if they would allow AI into the thoroughbred world, it would mean the gene pool would shrink because one horse could then cover thousands of mares.

Narrator: And anyone wishing to naturally cover their mare with Galileo needs serious financial backing. Even though his price is listed as private, it's widely reported that his stud fee sits at around $650,000, comfortably the world's highest. But because thoroughbred horses must be bred naturally, and therefore a collection of sperm cannot be purchased, equating the cost of Galileo's semen requires some extrapolation. Assuming that during the course of a natural covering, Galileo ejaculates the average of 50 mil of semen, and assuming that the semen is high-enough quality to impregnate a mare successfully, and assuming that a breeder paid $650,000 for that service, then we can deduce that a gallon of Galileo's semen could be worth a whopping $49 million, making it the most expensive liquid on earth. But is it worth it?

Matson: Like anything, there's a lot of work, there's a lot of luck in it. But you've got to make your luck, and you've gotta start off with the right genetics. The chances, obviously, you need to breed a lot to get that particular horse, but with the right genetics, you've got a much better chance.

Narrator: Galileo's position as the top sire is cemented by the achievements of his offspring. He has sired no less than 84 winners, including Frankel, who himself has now been put to stud, commanding the second-highest stud fee in the UK of around $220,000. In turn, he has sired a further 10 winners. Like father, like son.

Despite generally being safer for both stallion and mare, artificial insemination is criticized for its ethics around science and nature. But the analysis of thoroughbred-racehorse genetics has added to the controversy surrounding horse breeding. Roughly 10% experience orthopedic problems, and the majority suffer exercise-induced bleeding in the lungs. PETA investigators captured video from inside the breeding barns at Darley in Kentucky, one of the world's most expensive thoroughbred-breeding facilities, where stallions were goaded to cover more than 100 mares each in a breeding season. Some thoroughbreds were even sold for slaughter at a horse meat market.

With so much money to be made in racing, show jumping, dressage, and more, the price of horse semen will remain stable.