What Killed the Lechuza Polo Horses?

Polo is a demanding sport for both horses and riders, and the top international polo teams, sponsored by fabulously wealthy patrons, compete every year in South Florida. The culmination of the Palm Beach polo season is the US Open Championship, played at the International Polo Club grounds in Wellington. This year, a shocking tragedy unfolded Sunday as 21 horses from the Lechuza Caracas team collapsed and died, within hours after being unloaded from a trailer and groomed to play a match against Black Watch. These were undoubtedly the best horses in Lechuza’s string, in the prime of equine life, and at peak fitness and training. Many of the horses were owned by the team’s patron, Venezuelan businessman Victor Vargas, and each polo pony was valued at approximately US$100,000. However, it’s difficult to put a precise dollar value on all the training, conditioning, care, and breeding strategies that produced such elite equine athletes, and the Lechuza polo players have lost their trusted friends and talented teammates as well. Wellington veterinarians determined that the onset of illness was too sudden to be attributed to an infectious pathogen, but at this point the cause of death remains unknown, and is speculated to involve a toxin in the feed, water, injections, or supplements given to the horses.

Why is polo such an expensive sport, with international-level competition accessible only to the extremely wealthy? Obviously, the horses and their maintenance – feed, board, shoes, veterinary care, training- require a substantial amount of money. Unlike the related sport of polocrosse, which can be played competitively with just one horse, polo requires several horses for each player. A player at the level of low-goal “club” polo (which believe me, is sufficient adrenaline rush for most sane individuals) can compete with two to four horses in her string, which is manageable on an upper middle class income in some parts of the US. Mid- to high-goal polo, however, requires a string of at least six horses for each player on the team, i.e. one horse for each period, or chukker. And we haven’t even discussed club fees, tournament fees, grooms, or professional polo players who require payment.

Campeonata Mundial de Polo – photo by edcarsi under Creative Commons License

At this point I should explain some polo rules and terminology. First, “low-goal” vs. “high-goal” … what’s up with that? Well, every polo player has a numerical handicap, assigned by the club and the US Polo Association (or similar international organizations). A player starts at -2, and the highest possible handicap (for outdoor polo) is +10; realistically, you’re doing damn well to be rated at 0 or +1. In fact, I was over the moon for days every time someone told me I had made a “one-goaler play” in a polo match. There are only a handful of ten-goalers worldwide, and most of them are from Argentina. Polo leagues are set up according to the combined handicaps of the four players on each team. Typically, team handicaps for low-goal polo are between 4 and 8; for example, I (-1 at the time) once played on a team with another -1, a +1, and a +5, for a combined handicap of +4. In contrast, combined handicaps for teams competing in the US Open Polo Championship are as high as 26; with three players at 7 or 8 goals, and the patron at 1 goal, Lechuza Caracas has a team handicap of 23. The Black Watch team that Lechuza was to have played on Sunday has a handicap of 25, and the Crab Orchard team has a handicap of 26.

Polo in the Country – photo by Paul Keleher under Creative Commons license

OK, now that you have the goal thing sussed, why are so many horses required for each player? A polo field is 300 yards long and 160 yards wide, and the entire pitch (as well as bits at the ends and along the sides) is used again and again throughout the course of a chukker (thus the need for divot-stomping). Each chukker is 7 minutes long, with the clock stopped only for penalties, falls, and injuries. Any player on the team can score a goal, and no one is restricted to a particular section of the field, unless a penalty shot is being taken. The pace, at the very least, is a hand canter, and more often the gallop. Only the Thoroughbred horse has both the speed and the stamina for competitive polo, and each polo horse must be at its peak conditioning and aerobic capacity, to compete in a tournament like the US Open. A typical tournament match is six chukkers in length, and usually each horse plays only one chukker per game; in some cases, a player may switch horses mid-chukker, but the clock is not stopped for this substitution. Often the polo player will move from one horse to the other on the sideline, without ever dismounting, as the groom holds the two horses side-by-side. Broken mallets do not stop play either; the player must ride to the sidelines to retrieve a replacement, or if he is the better player, a teammate may quickly toss him a mallet. Polo horses must also be able to stop quickly, start quickly, turn, change direction mid-gallop, push opponent horses off the line of the ball, tolerate a mallet being swung under the neck and tail, and stand or walk forward reliably for the throw-ins. All of this is very physically demanding, and naturally, such ultra-buff and superbly conditioned animals require the best feed, vitamins, and supplements to stay at the top of their game.

NYC – AMNH: Horse-Polo – photo by wallyg under Creative Commons license

Which brings me, finally, to the science associated with performance horses, and the possible sources of toxins that may have caused the tragic deaths of the Lechuza polo horses. First, there are many plants, invasive or ornamental, present in the tropical environment of South Florida, which may be poisonous to horses. The needles and seeds of yews (Taxus species) contain toxic alkaloids, and half a pound of yew needles would be sufficient to kill a 1000-lb. horse (Wright et al. 2007). Creeping indigo (Indigofera spicata), which is planted for cover and erosion control, has invaded pastures in South Florida, and can cause a deadly central nervous system disease in horses that consume its leaves and seeds (Morton 1989). However, it seems unlikely that all 21 of the Lechuza horses would have consumed the same toxic plants -whether yew, creeping indigo, or another poisonous plant such as hemlock, oleander, or lantana – at the same time, and in amounts sufficient to cause death. Another possibility is that the feed or water for the Lechuza horses was contaminated … but then why did only some of the club’s horses fall ill and die, while others were spared? There have been incidents of numerous horse fatalities at a breeding facility or stables, following ingestion of feed contaminated with the antobiotic monensin (Doonan et al., 1989).

While contaminated feed remains a possibility, the question remains as to why only 21 of the horses in the barn died, and the answer is almost certainly related to the preparation of the affected horses for the tournament game. The involvement of anabolic steroids has been dismissed because such drugs are banned in some of the countries where the Lechuza team competes. However, it is not uncommon to inject performance horses with vitamins and antioxidant substances prior to a competitive event. Electrolyte and vitamin supplements may also be mixed with feed or in a bran mash, a treatment which is legal, innocuous, and potentially beneficial to the horse. White and colleagues (2001) reported that intervenous administration of the antioxidant ascorbate, prior to a race, can reduce the oxidative stress produced by intense exercise in Thoroughbred horses. The effects of vitamin E and ascorbate supplements on oxidative stress in Thoroughbred polo horses and in Arabian endurance horses have also been examined, with conflicting results (Williams et al. 2004).

Lipid peroxidation in mature (MAT) and older (OLD) Standardbred horses, before and after the 8-week training protocol. There were no significant effects of age or training on plasma lipid hydroperoxide (LPO) levels. From Williams et al. 2008

Recently, Williams and colleagues (2008) examined the relationship between aging and oxidative stress in the horse. In this study, two groups of Standardbred mares – eight mature (10-14 years) and 5 older (20-24 years) horses – were trained three to five days each week at a submaximal work intensity, and subjected to a graded exercise test before and after the 8-week training period. During the graded exercise test, the horses ran on a treadmill, at an incline of 6%, until they reached fatigue; heart rate was monitored at several different time points pre- and post-fatigue. Plasma lactate concentration, packed cell volume, total glutathione, cellular glutathione peroxidase, and lipid hydroperoxide were measured from blood samples. In addition, the researchers determined the apoptosis percentages in white blood cell samples, as an indicator of immune system function. Both mature and older horses responded to the training regime with physiological adaptations that helped them cope better with the oxidative stress induced by the second treadmill test. The older horses had a greater level of white blood cell apoptosis, which might be indicate that they could become immune-compromised under exercise, and could benefit from antioxidant supplements. However, unlike humans, older horses suffered no apparent decline in the ability to respond directly to oxidative stress, in the context of the treadmill fatigue test. The researchers speculated that a more intensely aerobic training protocol may be required to reveal significant differences between mature and older horses.

Toxic contaminants in feed and nutritional supplements are a concern for all horse owners, whether they are polo players, breeders, professional trainers, or amateur equestrians. Responsible horse owners and equestrian competitors want to keep their animals healthy and in top condition, and vitamin-mineral supplements are widely used. Let’s hope this sad incident was an isolated one.

UPDATE: The news from Wellington states that today’s semi-finals match has been postponed, as several inches of rain fell on the fields, making them unsafe for polo.

UPDATE 4/23: CNN is reporting that a veterinary supply company incorrectly prepared medications injected into the polo horses that died. Five horses that did not receive this series of injections did not become ill.

References:

Doonan GR, Brown CM, Mullaney TP et al. (1989) Monensin poisoning in horses – an international incident. Can. Vet. J. 30, 165-169.

Morton J (1989) Creeping indigo (Indigofera spicata Forsk.) (Fabaceae) – A hazard to herbivores in Florida. Economic Botany 43, 314-327.

White A, Estrada M, Walker K et al. (2001) Role of exercise and ascorbate on plasma antioxidant capacity in thoroughbred race horses. Comp. Biochem. Physiol. Part A 128, 99-104.

Williams CA, Kronfeld DS, Hess TM et al. (2004) Antioxidant supplementation and subsequent oxidative stress of horses during an 80-km endurance race. J. Anim. Sci. 82, 588-594.

Wright B, Jansen J, Leuty T (2007) Yew poisoning in horses and ruminants. Ontario Ministry of Agriculture, Food and Rural Affairs.

Williams, C., Gordon, M., Betros, C., & McKeever, K. (2007). Apoptosis and antioxidant status are influenced by age and exercise training in horses Journal of Animal Science, 86 (3), 576-583 DOI: 10.2527/jas.2007-0585