Saturday, May 28, 2011

EQUINE OBESITY: Can You Tell FAT from FIT?






These days, most of us don’t have to look too far to find someone whom we think could stand to lose a few pounds – often more than a few. We have no difficulty recognizing obesity in humans, and we generally understand that overeating and a lack of exercise are the major culprits in our growing propensity to pack on the pounds. In addition, we know that being overweight can have serious consequences for human health. When it comes to our horses, however, we are apparently failing to notice that there is a widespread and rapidly increasing problem with equine obesity, and many of us are not aware that overweight horses also face many health risks – some of which can be devastating.

A Bigger problem than most think (pun unavoidable!)

A recent study by a team of researchers at the Virginia-Maryland regional College of Veterinary Medicine and the College of Agriculture and Life Sciences at Virginia Tech is shedding new light on the prevalence of equine obesity, and the numbers are startling. While a 1998 owner-reported study conducted by the USDA’s National Animal Health Monitoring System (NAHMS) suggested that only 5% of horses were overweight, the Virginia study found that 51% of the 300 horses studied were overweight, and 19% were obese.  While it is possible that obesity (used here to mean any degree of excess fat) has increased dramatically in the last ten years, a more probable explanation is that horse owners tend to underestimate the degree of obesity in their own horses; therefore, any study relying on owner reporting is likely to be inaccurate.

Still, even the researchers were surprised by the scale of their findings. Says Dr. Craig Thatcher, a professor in the veterinary college’s Department of Large Animal Clinical Sciences and Diplomate of the American College of Veterinary Nutrition, “We thought it was at a level of at least 15 percent, higher than the NAHMS study, but we did not expect the numbers to be as high as they were.” One person who is not surprised by the Virginia team’s findings is Canadian scientist Shannon E. Pratt, PhD, PAS, an Assistant Professor in the Department of Animal Science at North Carolina State University. Explains Pratt, “We did a similar study and obtained remarkably similar results. In our study, two graduate students and I drove all over North Carolina to more than 50 different farms and took blood samples, body measurements, feed samples, weights, etcetera from 366 horses. We found that 48% of the horses had body condition scores greater to or equal to 6 on the 1-9 Henneke scale (5 is generally considered ideal; see sidebar) and 20% were considered “obese” (greater than or equal to 7). I’m sure if this was repeated in other states or in countries like Canada, we’d see similar results.

Evidence from England certainly suggests that the equine obesity problem is not just an American issue. The International League for the Protection of Horses (ILPH), based in Norfolk, UK, reports that in comparing 2006 to 2007, they had a 100% increase in the number of calls received from people concerned about overweight horses, and they also had a 1,000% increase in reports of laminitis – a serious health issue linked to equine obesity. These massive increases prompted the ILPH to launch a series of “Right Weight Road Shows” in which veterinarians and nutritionists travel to different locations to educate horse owners about obesity in horses. Their work is supported by the British Equine Veterinary Association, whose president, Dr. Josh Slater, believes that obesity in equines is under-recognized. “Obesity is certainly becoming more of a problem,” says Slater, “in part because people tend to see a fat horse as a healthy horse.”

Why Equine Obesity is on the Rise


As Slater suggests, misconceptions about what constitutes a healthy amount of fat on a horse are definitely a factor in the obesity equation – but just where do these misconceptions come from? The answer may lie in part in the influential realm of the show world. States Robert Eustace, FRCVS, founder of the UK’s Laminitis Trust, “The type of horse considered suitable to win a show class today is in fact obese. This ‘ideal’ then filters down the line.” Here in North America – particularly in Canada – we see a similar type of horse winning in certain classes. Says Amberlee Ficociello, a Quarter Horse breeder, competitor and owner of the Five Pine Ranch in Peachland, BC, “Obesity is rewarded in some aspects of the horse world.  In particular, the stock horse breeds are famous for their overweight halter horses.  These animals have been selectively bred for heavy muscling as well as certain conformation characteristics.  They are supposed to be representative of the ideal breed type, but in today's halter classes, weanlings on up to aged horses are fit up to body condition scores of  7 and up!  Heavy grain diets, limited outside turnout, and limited exercise all combine to create an overweight stock horse that is rewarded in the show pen for their size. The bigger the better, as they say.”

However, while some people point the finger squarely at the judges for pinning overweight horses, Ficociello says there is more to it than that. “It is the responsibility of the exhibitor, owner, breeder, trainer and judges to change this.  We are completely responsible for the choices we make, and for the goals we have for our animals.  The judges can certainly choose to not reward the heaviest horses but the most fit.  However, it is pretty difficult when five horses stand in a class and all five are overweight.  If each and every person involved in this aspect of the industry woke up tomorrow morning and decided to start their day with a more healthy and fit horse, we could change this.”

Some in the industry feel that change is already underway. Breeder and trainer Laurie Takoff, of Laurian Quarter Horses in Kelowna, BC says, “Years and years ago halter horses used to be very, very fat. Nowadays, leading trainers and judges want an extremely fit horse; however, in saying that, up here in Canada and the Pacific Northwest we are behind the times.  People are still trying to show these soggy, fat horses in hopes of doing well.  For myself, I want my halter horses to look beautifully fit with good flesh, but also able to move so well that the judge can't wait to see the horse move, or better yet ride. You can't have a Sumo wrestler move and look like a fit athlete or dancer!  Still, folks in the know are well experienced that fat can hide a lot of flaws.”
            
            While the tendency to reward fat horses in the halter ring – and in hunter shows, as well –  remains an issue in some places, there are clearly other factors at play. It is probably obvious that diet is a major contributor to equine obesity, yet many people don’t realize that the feeds and forage their horse is consuming may be far in excess of the horse’s actual caloric requirements. This is especially true when it comes to grass. Because horses are grazing animals, we generally believe that it is perfectly natural for them to be out in a field of grass, munching away to their heart’s content. This scenario, however, is far from natural, for several reasons. Firstly, the horse evolved in areas where forage was sparse. This had the effect of limiting the overall amount of forage consumed, but it also required the horse to walk many miles a day just to find enough to eat. Modern feral horses have been observed traveling up to 25 miles a day in their foraging efforts, and that kind of exercise, along with a more limited feed intake, keeps the metabolism of free-roaming horses revved up, and their weight down. By contrast, domestic horses on pasture often have as much as they can eat within easy reach, requiring very little expenditure of energy.

When you couple this easy access with the fact that today’s grasses are also anything but natural, you have a recipe for disaster. Explains Dr. Pratt, “Today’s grasses have been designed for cattle – not horses – so they are definitely richer than what a horse needs.” Specifically, the agricultural industry has created “improved” grass varieties that are significantly higher in sugar and protein than many native grasses. This is a great benefit if you are trying to put weight on beef cattle or get higher yields out of dairy cows. Unfortunately, that same benefit becomes a liability for horses, who are simply not equipped to deal with such nutrient-dense forage.

            High sugar grasses – and the high sugar hays produced from them – can be especially troublesome for some horses, causing them to pack on the pounds and putting their health at risk. Part of the problem is due to the fact that many horse owners simply have no idea that “plain old grass hay” can actually be up to 30% sugar. Even those who are aware of the harmful potential of high sugar hay may not realize that even coarse, first cut, or yellowed hay can still be high in sugar. Ken Wilkinson, nutritionist at the Otter Co-op in Aldergrove, BC, used to be comfortable simply recommending coarser, first cut hays to people with overweight horses or those prone to laminitis, but now he prefers to test it first. “We’ve done a lot of hay testing over the last few years,” he explains, “and I’ve been very surprised at some of the numbers that have come back on what I was pretty sure would be low sugar hay. The bottom line is that there is just no way to know by looking at a hay whether it is high or low sugar.”

            Wilkinson also points out that environmental variability and changes in farming practices can cause even hay from the same field to vary in its sugar level from year to year or cutting to cutting. This assertion is born out by hay grower Gordon McEachern of Chilliwack, B.C., who says, “I recently cut three fields of the same type of grass on three different days, and because the weather was cloudier one day and I cut at a different time of day on another, all three hays tested out differently. Not only did the sugar fluctuate, but even the protein and mineral content were different. I’ve also found that you can cut one field all on the same day, but if you leave some of it longer before you bale it, the sugar tends to go down a bit.”

            McEachern aims to produce hay that is more geared towards the needs of horses than cattle, and as a former dairy farmer, he knows the difference. “A lot of the hays you see out there are really not appropriate for horses and will definitely put too much weight on them,” he says. “It’s sad because people want to do the best for their horses, yet they are quite literally killing them, in some cases, with these rich hays.” McEachern explains that there are things you can do when growing and cutting hay to try to produce a lower sugar, more horse-friendly product. “You want to make sure you prevent stress from  drought or other factors, but you don’t want to over fertilize. You also get a lower sugar hay if you cut when it is cloudy or during the night due to the longer drying time, and I’ve found that it pulls down the protein and sugar some if you wait a little bit longer than usual between cuttings, say seven weeks instead of five.” Even so, he tests every cutting, as he knows that even a small difference in sugar can have a significant impact on some horses, especially those with metabolic disorders or those prone to laminitis.

As for grain, the Virginia study found that improved forages are likely a more significant contributor to equine obesity than grain, even though grain is what most often comes to mind when we think of overfeeding horses. In fact, the majority of the horses assessed in the study received little in the way of grain or concentrates, with the bulk of their diet consisting of pasture and hay.  Nonetheless, any horse that has even a slight tendency to put on fat should likely have the grain removed from its diet. Says Dr. Pratt, “I think most horse owners have been trained to feed grain, even if their horse doesn’t need it – and most don’t.  In general, a horse at maintenance can get all of his nutrient requirements from good quality hay, a salt source and water.”  Adds Wilkinson, “We’re using a lot less grain for horses now, as the hay analyses we are doing are giving us a more accurate picture of what is in the hay. With the richer hays, you just don’t need to supplement like that.”

Another reason why we are seeing so many fat horses these days is that many people don’t work their horses hard enough to burn up the calories they take in. As Dr. Pratt states, “People tend to overestimate how much feed horses need, and they often underestimate how much exercise they need.” The very light work load most horses are asked to do, coupled with the fact that many horses are kept in stalls or small enclosures for part or all of each day, has forced our horses to become the equine equivalent of couch potatoes. And, as in humans, the lack of exercise not only means that calories go unused, it also has a negative impact on the horse’s overall metabolism, making weight gain even easier.

Why it matters


Whatever the reasons for a horse’s weight gain, the consequences can be extremely serious. As Dr. Pratt explains, “Being overweight is definitely a big health risk for horses. First off – a horse is already carrying 1000 lbs, give or take, on four relatively small hooves. Any excess weight just adds more concussion to the joints and feet, which increases the risk of bone, tendon and joint injuries. But more importantly, adipose (fat) tissue is now known to be an endocrine organ – not just a storage place for energy – producing hormones and even inflammatory proteins. As such, obesity is considered an inflammatory state. Obesity is also associated with insulin resistance and laminitis, though research in this area is ongoing.”

It was, in fact, the recent increase in pasture-associated laminitis (commonly referred to as “grass founder”) that first inspired the Virginia study. Dr. Scott Pleasant, another member of the Virginia team, notes that “Laminitis is one of the most devastating and debilitating problems that we see with the horse. It occurs when there is a failure of the connective tissue bond between the horse’s hoof and the bone within the hoof – typically due to some form of inflammation. When that bond fails, and the hoof and bone start to separate, it is extremely painful to the horse.” The team theorized that overweight horses may have chronic inflammation, imbalances of insulin and glucose (sugar), as well as oxidative stress, which results from changes to metabolic processes that are related to the destruction and creation of new cells in the body. All of these are believed to be factors in laminitis, which is a leading cause of death among horses, second only to colic.

Unfortunately, the bad news doesn’t stop there. According to Les Burwash, Manager of Horse Programs for Alberta Agriculture in Airdrie, AB, “In addition to having an increased risk of injury, overweight horses tend to be less athletic and perform at a reduced level. They fatigue more easily and have increased sweating because the fat acts as a layer of insulation, reducing the body’s ability to cool down. This also makes them more susceptible to hyperthermia (overheating) during exercise than horses with body condition scores of less than 7.” Owners of young stock should also be aware that growing horses allowed to become overweight may be at increased risk for developmental orthopedic disease (DOD).

What you can do


            The first step in preventing your horse from falling victim to the health problems associated with obesity is making sure that you recognize what a healthy weight looks like. One of the best ways to do that is to get familiar with the Henneke scale, then assess your horses on a frequent basis to make sure they are staying within the desired range for their usage. Keep in mind that heavy winter coats and blankets can make it harder to assess the horse visually, so you may have to rely more on feel.

If you do have an overweight horse, it is important not to put the horse on a severe crash diet, as this can create problems too. “Overweight horses must have their weight reduced slowly and carefully,” states Dr. Pratt. “I would recommend that the owner work with a nutritionist to take a close look at the hay, weigh all of the feeds, figure out if any nutrients need to be included in a concentrate, and set up a plan to slowly reduce the energy intake to facilitate weight loss.” When working with a nutritionist, however, be sure to choose someone who is not obligated by their employer to push certain products which may not always be the most appropriate for your horse’s needs. Also make sure that any increase in exercise is introduced gradually, and consult with your veterinarian before encouraging any exercise with a horse that has acute or chronic laminitis.
            
            Obesity in horses is a preventable problem, but it requires both education and dedication. It might make you feel good to dole out great quantities of hay, grain and treats, and sure your horse will look content standing shoulder deep in rich green grass. But in the end, there is no getting around the fact that if you really love your horses, you will do what it takes to make sure they are maintained at a healthy – not hefty – weight.


Sidebar: The Henneke Scale

The Henneke Body Condition Score (BCS) system, developed as part of a research project at Texas A&M University in the early 80s, has become the most widely accepted method of evaluating the amount of fat a horse is carrying. Using both sight and touch, the evaluator assesses six specific areas on the horse. These areas were chosen because they are not places where one could confuse fat with muscle.  Each area is ranked on a scale of 1-9, then an overall score is assigned based on the number that appears most often in the six areas. In general, a score of 5 is considered ideal, but studies have shown that broodmares conceive and maintain a pregnancy more easily and have fewer post partum problems if they have a score no lower than 6 and up to 8. Breeding stallions also fare better if they start off the season at a 6-7. However, if the individual is at risk for laminitis or other weight-related problems, maintaining body condition above the 5-6 range may not be worth it. Note: Though not widely used, there are other BCS systems out there that have different ranges for assessment. The Carroll and Huntington version, for example, goes from 0-5. Be sure you know what scale is being used when discussing body condition scoring.

Below are the six areas used to assess a horse, along with a description of what you are looking and feeling for.

1. Neck                                                                                             
     a. Bone structure of the neck is easily noticeable (1-2)
     b. Bone structure of the neck is accentuated (3-4)
     c. The neck ties smoothly into the withers (5-6)
     d. Fat deposits are found along the neck (7)
     e. Neck thickened/bulging fat showing around the crest (8-9)         

2. Withers
     a. The withers are easily noticeable or discernable (1-2)
     b. Withers are accentuated (3-4)
     c. Withers appear rounded over spinous processes (5)
     d. Fat may be deposited along sides of withers (6-7)
     e. Areas along withers filled with fat (8-9)                                      

3. Crease down the back 
     a. Spinous processes projecting prominently (1-2)
     b. Spinous processes easily discernable or accentuated (3-4)
     c. Appears rounded over spinous processes/slight crease (5-6) 
     d. may have a crease showing down the back (7)
     e. Obvious crease showing down the back (8-9)

4. Ribs
     a. Ribs are prominent (1-2)      
     b. Slight fat over the ribs or discernable by faint outline (3-4)
     c. Ribs are not distinguishable by sight (5)
     d. Fat over ribs feels spongy (6-7)
     e. Difficult to feel ribs due to patchy fat (8-9)

5. Tailhead
     a. Tailhead projecting predominantly (1-2)
     b. Tailhead prominent but individual vertebrae not seen (3-4)
     c. Fat around tailhead is soft or spongy (5-6)
     d. Fat around tailhead is very soft (7-8)
     e. Bulging fat around tailhead (9)

6. Behind the shoulder
     a. Bone structure of the shoulder is easily noticeable (1-2)
     b. Shoulders are accentuated (3-4)
     c. Shoulders blend smoothly into body (5)
     d. Some fat is deposited around the shoulders (6-7)
     e. Fat is easily seen behind the shoulder (8-9)

To view example photos of horses that fall into the 1-9 assessments, go to:



Sidebar 2: Fat Horses and Insulin Resistance

(See complete article on Insulin Resistance on this blog)

In recent years there have been a spate of studies examining insulin resistance (IR) in horses, a condition in which the cells in the body become insensitive to the action of insulin. Horses with IR are extremely vulnerable to laminitis and must be treated accordingly. They are also usually extremely easy keepers and are very often overweight. 

While there appears to be a close link between obesity and IR, some people have mistakenly come to believe that virtually all fat horses must have IR. However, as Dr. Pratt points out, this is simply not the case. “I think the insulin resistance bandwagon is likely a bit overdone,”she says. “Not all obese horses are insulin resistant – and I think it is important for horse owners not to assume their overweight horse is IR, but rather to find out by working with their veterinarian. A vet can get a blood sample taken (the horse should have no grain/concentrate or exercise within 6 hours; hay is fine) to look at insulin and glucose concentrations. While not indicative of IR on their own, a single blood sample can usually pinpoint a problem if the numbers are off. Ideally, the vet will take a couple of samples under similar conditions over a few days). Then the vet can work to do more complicated tests to confirm IR if warranted.” 

It is worth noting that horses with IR often have abnormal fat distribution that shows up in the crest, which becomes thick and hard, and in extra “pads” of fat behind the shoulder, around the tailhead, in the sheath of males, or as a “fullness” above the eyes.  


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