Nutrition-associated problems facing elite level three-day eventing horses
Reasons for performing study: The main goal of feeding elite 3-day event horses is to deliver nutrients in optimal amounts to allow the horse to maximize its health and performance. However, improper nutritional management and/or physiological stressors related to intense training and competition may increase the risk of nutrition-associated disorders in these horses. An understanding of the nutrition-associated problems contributing to poor performance is critical to the health and welfare of the horse.
Objectives: To characterize the nutrition-associated problems affecting top level 3-day event horses during 2008.
Methods: Contact information for riders competing in the 2 highest levels of 3-day eventing in 2008 was obtained from the United States Eventing Association. A survey containing 10 questions pertaining to participant demographics and nutrition-associated problems experienced by their horses was mailed and e-mailed to the 81 individuals fitting our criteria of living in USA and Canada. Data was collected in April and May 2009.
Results: Twenty-nine of 81 riders completed the survey (35.8%). Respondents rode a total of 45 horses in top level 3-day events in 2008. The top 5 nutrition-associated problems that horses faced at a significantly higher level than the other problems (P<0.0001) were gastric ulcers (42.2%), joint problems (37.7%), decreased appetite (31.1%), weight loss (31.1%) and hyperexcitability (22.2%). There was no significant difference in frequency of problems between home and competition (P = 0.22).
Conclusions: Horses competing at a high level of 3-day eventing in 2008 were at risk of reduced performance given the significant rate of gastric ulcers, decreased appetite and weight loss. Research addressing specific causes of and/or feeding management changes that would reduce the incidence of these problems in these horses is needed to ensure optimal health and performance.
The primary objective of feeding an elite-level 3-day event horse is to provide the appropriate amount of nutrients to maximise health and performance. According to the 2007 edition of the National Research Council's (NRC) Nutrient Requirement of Horses, the energy, protein, vitamin and mineral requirements of horses involved in elite 3-day eventing are 1.5–2.0 times that of a horse at maintenance. The highest nutritional requirement category includes equine athletes involved in elite level 3-day eventing, Quarter Horse/Thoroughbred/Standardbred racing and endurance riding (Anon 2007). Ideally, all diets fed to horses should be high in fibre from a roughage source such as pasture or hay, but the diet of the performance horse often must be supplemented with concentrate to meet the increased nutrient and energy demands. Unfortunately, feeding the equine athlete a diet high in concentrate may lead to one or more health problems that can reduce athletic performance (Clarke et al. 1990). While there may be many contributing factors to the multiple health problems observed within this study, the fact that these elite athletes have concentrate intakes of 1.5–2 times the amount fed to a horse at maintenance or in light work lends high potential for the underlying cause to be related to a high plane of nutrition.
The governing body for international 3-day eventing, The International Federation for Equestrian Sports (FEI), divides the sport into 4 levels of competition or difficulty. The highest or Olympic level is denoted as Concours Complet Internationale (International 3-day event) Four Star Event (CCI4*) followed by the CCI3*, CCI2* and CCI1* levels. The CIC (Concours International Combiné) or International one-day event uses the same star level system; however, the competition takes place over one or 2 days and features a shortened cross-country course. The purpose of this study was to characterise the nutrition-associated problems that plagued CCI/CIC3* or CCI/CIC4* level event horses during the 2008 competition season.
Materials and methods
A survey consisting of 10 questions was developed to gather information about rider demographics, number of horses they competed in CCI/CIC3* and CCI/CIC4* events in 2008, incidence of 18 nutrition-associated problems experienced at home or during competition by those horses in 2008 and rider perception of the importance of different feeding management goals. Prior to completion of the survey instrument, a list of problems both directly (such as weight loss or decreased appetite) and indirectly (such as joint and hoof problems) possibly related to nutrition was reviewed and revised by veterinarians specialising in equine sports medicine in order to ensure survey completeness. The survey concluded with a question asking if riders would be willing to participate in future research for the purpose of evaluating the effects of particular nutritional treatments on the performance of their 3-day event horse.
Mailing addresses of all 81 riders from the USA and Canada who competed at the CCI/CIC3* and CCI/CIC4* level in 2008 were obtained from the United States Eventing Association (USEA)1. Email addresses for 17 of the 81 CCI2*/CCI3*riders were obtained from a previous study conducted by the authors in 2007 for the purpose of sending electronic notices. All 81 riders were mailed the survey instrument following a modified multiple wave mailing technique outlined by Dillman (2000). In Week 1 of mailing, riders were mailed a postcard explaining the purpose of the survey. During the following week, all participants were mailed a cover letter, paper survey and a stamped return envelope addressed to the authors. Within the cover letter, riders were also given instructions on how they could complete an online version of the survey (SurveyMonkey.com)2 rather than submit a mailed paper copy. On Week 4, a postcard was mailed to all participants to remind them to return the survey. On Week 6, the data collection period ended. Data were collected during April and May 2009.
Data for the nutrition associated problems experienced and the location where they were experienced (at home or at competition) were analysed using the GENLIN procedure of PASW (previously known as SPSS) Statistics 173. The unit of analysis (the subject) is the rider since each respondent completed only one survey regardless of how many horses the rider owned or how many competitions the rider entered. Since these responses were frequency counts (the number of times a nutrition associated problem was experienced in each location), a Poisson distribution was assumed. Because responses to the nutrition-associated problems from the same respondent are not independent (the same rider responded to multiple questions regarding 18 problems at home and at competitions, resulting in correlated within-subjects data), a generalised estimating equations (GEE) approach was used to account for the correlated nature of the responses. The GEE model can be stated explicitly as:
where yijk is the frequency count of the ith problem in the jth location by the kth rider, µ is the overall mean, αi is the ith problem (i= 1 to 18), βj is the jth location (j= 1 to 2) (αβ)ij is the interaction between problem and location, and εijk is the residual error, assumed to follow a Poisson distribution.
In addition, since some respondents owned more than one horse and some entered their horse(s) in more than one competition, responses to the problems were inversely weighted by the number of horses owned and by the number of competitions entered. For example, a rider who owns 2 horses and entered them both in 5 competitions has a much greater chance of observing a nutrition associated problem than does the rider who owns one horse and entered only one competition. Weighting responses by the number of horses owned and number of competitions entered attempts to equalise the probability of observing a nutrition associated problem across riders. An alpha level of 0.05 was chosen for all statistical tests.
Twenty-nine of the 81 total riders (36%) completed the survey, with one completing the online version. Average age of riders was 35.3 years (Range: 21–59 years). Respondents competed a total of 45 horses in CCI/CIC3* and CCI/CIC4* events in 2008. The majority of riders (20) competed one horse, 6 riders competed 2 horses, 2 riders competed 4 horses and one rider competed 5 horses. The majority of riders (20) entered their horses in 3 or fewer competitions while one rider reported entering as many as 10 competitions. Riders indicated that they spent the majority of time training their horses in Florida (21%), California (14%), Pennsylvania (14%), Virginia (14%), South Carolina (10%), Alabama (3%), Arizona (3%), Louisiana (3%), Maine (3%), New Jersey (3%), New York (3%), North Carolina (3%) or Washington (3%). Sixty-five percent of the riders indicated that they were willing to participate in research at 3-day event competitions for the purpose of evaluating the effects of a particular nutritional treatment on their horse's eventing performance. Riders also indicated that their top nutritional goals when feeding their competition horses were meeting nutritional requirements, preventing a performance failure, and enhancing their horse's performance, while promoting weight loss was their least important goal (Table 1).
Table 1. Importance of feeding management goals when feeding CCI/CIC3* or CCI/CIC4* 3-day event horsesa
|Meet nutritional requirements||0||0||6.9%||89.7%||3.4%||2.93|
|Promote weight gain||14.3%||10.7%||39.3%||32.1%||6.8%||1.93|
|Promote weight loss||79.3%||3.4%||10.3%||3.4%||3.4%||0.36|
|Improve hair coat appearance||0||10.3%||51.7%||34.5%||3.4%||2.25|
|Prevent performance failure||0||0||10.3%||86.2%||3.4%||2.89|
In this study, 100% of horses experienced at least one nutrition-associated problem. The top 5 nutrition-associated problems experienced were gastric ulcers (44%), joint problems (38%), decreased appetite (33%), weight loss (31%) and hyperexcitability (22%; Table 2). Fewer than 10% of the horses in the survey experienced colic, diarrhoea, feed allergies, hoof problems, heat exhaustion, anhydrosis (lack of sweating), laminitis, long recovery time, fatigue, tying-up and weight gain. None of the respondents' horses experienced synchronous diaphragmatic flutter (Thumps) or toxic plant ingestion during the 2008 data collection period. Results from the statistical analysis found no significant difference between home and competition in the frequency of each nutrition associated problem i.e. the interaction of location and problem was not statistically significant and neither was the location main effect. The problem main effect was highly significant (P<0.001; Table 3), indicating that all problems were not reported at the same frequency.
Table 2. Percentage of horses competing in CCI/CIC3* or CCI/CIC4* events in 2008 that experienced a nutrition-associated problema
|Lack of sweating||93.1||6.9||0||0||0||0||4.4|
|Long recovery time||93.1||6.9||0||0||0||0||4.4|
|Synchronous diaphragmatic flutter (Thumps)||100.0||0||0||0||0||0||0|
|Toxic plant/weed consumption||100.0||0||0||0||0||0||0|
Table 3. Percentage of riders (n = 29) noting the number of times their CCI/CIC3* or CCI/CIC4* event horses experienced nutrition-associated problems while training at home or at competition in 2008a
|Lack of sweating||6||3|
|Long recovery time||3||2|
|Synchronous diaphragmatic flutter (Thumps)||0||0|
|Toxic plant/weed consumption||1||0|
The diet of the elite 3-day event horse must provide the nutrients required for performance and enable the horse to counteract the physical stress of training and competition (such as recovery and weight maintenance). There are many nutrition-associated factors that directly or indirectly contribute to the success or failure of equine athletic performance, including dietary components, gastrointestinal issues, weight maintenance, fluid and electrolyte balance and joint issues.
In a previous eventing study it was found that 76% of competing CCI3* riders interviewed stated that they fed a commercial feed product as well as a cereal grain, beet pulp, wheat bran or rice bran product to their horses at an average 13.7 ± 0.9 kg/day on an as fed basis (Burk and Williams 2008). The ratio of hay-to-concentrate fed during competition was 62:38. It is likely that this diet is very similar to the diets fed to the horses in the current study because a large percentage of the respondents in the current study had participated in the previous eventing study (Burk and Williams 2008). Providing a large amount of concentrate in the diet is necessary to meet the energy and nutrient requirements of the elite equine athlete (Anon 2007). Although this diet is nutrient rich, feeding it over a prolonged period of time (throughout a horse's eventing career) may lead to a variety of physiological issues that may result in decreased performance. Interestingly, 100% of horses in this study experienced at least one nutrition-associated problem.
Nutrition-associated problems of the gastrointestinal system
Given the high incidence of gastric ulcers, decreased appetite and weight loss experienced by the CCI/CIC3* and CCI/CIC4* event horses in this study, it is likely they were at an increased risk for reduced health and performance.
Gastric ulcers: Equine gastric ulcer syndrome (EGUS) is prevalent in performance horses due to many contributing factors such as exercise intensity, high concentrate diet, transportation, stress of competition, intermittent feeding and long-term use of nonsteroidal anti-inflammatory drugs (Reese and Andrews 2009; Videla and Andrews 2009). Rabuffo et al. (2009) found that 75% of 3-day event horses examined by gastric endoscopy had gastric ulcers. Our study found a relatively high percentage of riders reporting occurrence of gastric ulcers (almost half) in top level 3-day event horses. It is highly likely that the percentage of horses with gastric ulcers may have been higher in the present study if all horses had been examined via gastric endoscopy, although it is unclear what percentage of horses were actually diagnosed this way. In addition to veterinary diagnostics to confirm gastric ulcers, the riders often attribute observational criteria such as poor appetite, intermittent mild colic, and change in behaviour or poor performance to the incidence of gastric ulcers. Horses competing at elite level competitions may have EGUS but not show clear signs or they may display symptoms that can be attributed to other issues, such as a poor attitude, which was reported at least once in each of the survey questions asked (Tables 2, 3). Clinical signs of EGUS include acute and recurring colic, partial anorexia or poor appetite, poor endurance, inadequate energy and chronic diarrhoea (Videla and Andrews 2009). Many of these manifestations of EGUS were reported in the horses represented in this study.
Elite 3-day event horses are exercised intensely in order to stay fit for competition, and this may be another contributing factor to the high occurrence of gastric ulcers in horses reported in the current study. A study performed using a high-speed treadmill indicated that exercising horses experience a decrease in stomach volume due to an increase in abdominal pressure and this may cause the contents of the lower stomach to reflux towards the oesophagus, thus causing irritation and increased incidence of ulcers (Orsini et al. 2009).
Decreased appetite and weight loss: Over 30% of the horses in this study were reported to have decreased appetite while training at home and at competition, which may have resulted in weight loss. The probable cause of reduced appetite and subsequent weight loss in elite athletes is varied. Gastric ulcers are associated with poor appetite primarily due to the pain experienced by the horse in association with eating (Videla and Andrews 2009). Also, intense exercise is associated with increased production of hormones such as leptin and ghrelin that may lead to a decrease in appetite (Meier and Gressner 2004; Gordon et al. 2007). Hormone concentrations also change in response to feed (quantities, types and concentrations). Additionally, intense exercise coupled with adjusted concentrations may suppress appetite, but this has not been extensively investigated in the horse.
Fluid and electrolyte associated problems
Elite level 3-day event horses face a challenge of thermoregulation as well as restoring fluid and electrolyte balance, especially after the cross-country jumping phase of competition. There are many physiological issues that can arise that are directly related to heat accumulation and fluid/electrolyte imbalance (Kronfeld 2001a,b,c).
Heat exhaustion and long recovery time: Horses use evaporative cooling by means of sweating to thermoregulate (Hodgson et al. 1993). Excessive sweating can lead to dehydration and a decrease in circulating blood volume. Changes in electrolyte concentrations can lead to heat exhaustion (Kronfeld 2001a,b,c), as reported in a small percentage of the horses in the current study. Horses not adequately hydrated prior to exercise have a compromised thermoregulatory function. A decrease in plasma volume resulting from even minor dehydration can lead to hyperthermia and fatigue, since a smaller volume of blood comes in contact with the skin to dissipate heat (Kronfeld 2001a). Reduced blood volume can also diminish fluid supply available for sweating, which reduces the ability to dissipate heat (Hodgson et al. 1993). However, when horses are given water and supplemented with commercial electrolyte formulas or sodium chloride salt blocks, recovery is hastened (Kronfeld 2001b). In 2007, 92% of horses competing in a CCI3* level 3-day event were supplemented with electrolytes (Burk and Williams 2008). This practice may have contributed to the low incidence of both heat exhaustion and a long recovery time reported in the current study.
Exertional rhabdomyolysis: Rhabdomyolysis, or tying-up, is defined by severe damage to skeletal muscles and can be caused by intense exercise or genetic predisposition (Valentine 2005). Clinical signs of rhabdomyolysis usually present soon after the onset or immediately following the cessation of exercise. While not statistically different, cases of rhabdomyolysis reported in this study were 4 times more frequent at competition than at home. These findings coincide with the intense exercise associated with cross-country jumping and may be physiologically significant since it can result in elimination from competition. Rhabdomyolysis been linked to deficiencies of specific electrolytes, vitamins and minerals, as well as diets rich in grains (McKenzie and Firshman 2009).
Joint problems were reported in almost half of the horses represented in the current study. Elite 3-day event horses training intensely risk increased wear and tear on the joints and soft tissues. Additionally, very young horses put into training, such as those going into racing or eventing, are at risk of developmental orthopaedic disease due to the stress on the joints that are still growing (Lepeule et al. 2009), as well as nutrition and genetic predisposition. These injuries, when sustained early in life, could be contributing factors to the issues facing the horses in this study. Although many joint problems are not directly associated with underlying dietary causes, pain in the joints can be eased with the use of commercial oral joint supplements that contain some level of glucosamine and chondroitin sulphate or other anti-inflammatory or anti-arthritis compounds (Richardson and Loinaz 2007). Burk and Williams (2008) documented that joint supplements were the second most popular feed additive among competitors in a CCI3* 3-day event, with 43–60% of horses receiving supplementation. The statistically significant (P<0.0001) percentage of joint issues reported in our current study provides additional information to the broad picture of health concerns in elite event horses.
Home vs. competition
There were no differences observed between the number of times the nutrition-associated problems were experience at home or during competition. The problem main effect was highly significant, indicating that all problems were not reported at the same frequency. Joint problems, anhydrosis, fatigue and weight gain occurred numerically more frequently while training at home than at competition (1.6, 2, 2 and 9 times higher, respectively) and even though this difference was not statistically significant, it could be physiologically significant and therefore worth mentioning. Hyperexcitability, exertional rhabdomyolysis and decreased appetite occurred numerically more often at competition (2, 4 and 2.5 times higher, respectively). Again, these problems at competition could be extreme enough to prevent completion of the event, therefore are physiologically significant and need to be investigated for methods prevention or proper feeding management practices that could be implemented.
The most prevalent physiological problems were those relating directly to the gastrointestinal system. Gastric ulcers, as well as decreased appetite and resulting weight loss, were common among the elite 3-day event horses in this study. Other issues experienced frequently by these horses were associated with fluid and electrolyte balance, which can have a negative effect on performance and especially recovery after cross country. This survey study, while observational in nature, is important to statistically document the incidence of nutrition-associated problems experienced by top level 3-day event horses. However, additional research is needed to identify more specific risk factors, evaluate time at risk for each problem and determine more specific causes of the more prevalent problems in these horses. Nutritional evaluation of diets fed and how they affect performance should be investigated as well to identify potential solutions to nutrition-associated problems in elite event horses.
The authors would like to thank the riders who took the time to fill out the survey and the veterinarians who helped revise the survey. We also thank A. B. Howard, Statistical Software Support and Consulting Services, University of Vermont for assistance with the statistical analysis, as well as Mrs. E. Leahy and J. Willard for help with the final round of edits.
Conflicts of interest
The author has declared no potential conflicts.
1 USEA, Inc., Leesburg, Virginia, USA. http://www.useventing.com
2 Survey Monkey, Portland, Oregon, USA. http://www.surveymonkey.com
3 PASW, Chicago, Illinois, USA.