What is an appropriate expectation for rate of weight loss in an obese horse? This week, I dig into what the research says and compare that to Wilma's weight loss journey as well a couple client's horses.
It's been over 60 days since Wilma arrived. She's had her teeth floated (they were pretty bad) and a fecal egg count done (also pretty bad) which resulted in a strong dewormer being administered. Extra large cinches have been acquired, and her new EasyBoots have been sprayed bright pink so that they can be found if lost during fall rides in the tall grass. I also have someone coming to ride her several days a week which is a big step in her weight loss journey too! All of this is to say, it's taken a couple months to get her adjusted to life at Sullivan Horse Farm. With every new horse, I'm reminded just how long it takes to get horses settled into a new routine, how much longer it takes to really get to know them, and how much longer past that it takes to gain their trust and build confidence. Really, it's a full year process.
But the rate of training progress is not why we are here reading/writing this article now is it? What I'm here to discuss is the rate of weight loss. To my simple brain that means measuring the average pounds lost per day. If we have two dates with an amount of weight change between those dates, what is normal and safe? What I mean by "SAFE" is that the forage and feed restriction is done is such a way that the horse does not develop colic, ulcers, or other negative behaviors. I've been in the equine nutrition business for over 20 years and have developed an intuitive expectation from experience for what is normal and safe. However, I wanted to challenge my assumptions by digging into equine weight loss research results. I came across a handful of peer-reviewed journal articles from the Journal of Equine Veterinary Science that offered me a range of "rates of weight loss". Luckily, I wasn't too far off...phew!
WHAT DOES THE RESEARCH TELL US?
Ok, so we're ready to compare Wilma's rate of weight loss to what the research tells us is to be expected.
Garland et. al., 2023 Study = 0.96 lbs lost per day
In this study, researchers at the University of Guelph, Ontario, Canada, compared the weight loss results of four obese equine groups over a ten week period; daily exercise only, feed restriction only, exercise plus feed restriction, and an unrestricted sedentary control. Feed restriction was defined as 85% of the horse's digestible energy requirements and exercise was defined as 20 minutes 5 times per week. As you would imagine, the horses with both feed restriction and exercise lost the most weight (36 kg = 79.2 lbs = 1.13 lbs per day) and the control horses lost the least weight (28 kg = 61.6 lbs = 0.88 lbs per day). What is very interesting about the results of this study is that the feed restriction only group lost nearly equal amount of weight to the control group, which is consistent with my experience with Wilma. She did not lose significant weight until she was in consistent work!
Dugdale et. al., 2010 = 1.98-2.04 lbs lost per day
If we use Wilma to duplicate the results of this study, we have to understand one very important thing; ponies in the UK were used in the study, so it could be inaccurate to extrapolate to a draft cross like Wilma (but we're going to anyway). So, if she were a participant in this study- though assuredly an unwilling one- she would have lost about 28 kg (61.6 lbs) in the first week and progressively another 4.35 kg (9.57 lbs) every week for another 11 weeks for a total of 167 lbs of weight loss. She would have started at 1,430 lbs and finished at 1,263 lbs after 12 weeks of being fed 1% of her original body mass (only 14.3 pounds of hay per day). Now, the feed restriction in this study was far more severe than the first study which is why these researchers achieved much greater weight loss with feed restriction alone. But that's a good lesson to learn!
Gill et. al., 2106 = 0.38-0.47 lbs lost per day
This study is interesting and unique, because researchers used horses in their home environments to describe equine weight loss management! Twenty four horses in North Carolina were tracked between September and May, but kept in their same management situations. Some of the horses had unlimited access to pasture, some had 1/2 pasture and 1/2 restriction, and the other group had no access to pasture. The majority had no change in exercise. Diets were evaluated at the beginning of the study and owners + horses were sent home with instructions how to decrease digestible energy intake by 10-20%. Across all three management types, horses lost about 31.48 kg (69.3 lbs) over 182 days which is an average of 0.38 lbs per day. This is a lot less than in the research managed studies above- that makes sense, because owner compliance is much lower than researcher compliance to weight loss protocols. Using Wilma again as an average participant in this study (she'd be in the 1/2 pasture and 1/2 restriction category), I applied the overall results of 6% decrease in body weight. She would have lost 85.8 pounds over 26 weeks while restricting forage to 1.25-1.5% of her body weight. That's an intake range that I shoot for when decreasing body condition scores, so I was happy to see that modest weight loss could be achieved over several months.
All of these studies support each other as well as my basic assumptions about the rate of weight loss in horses. Here are the three take-a-way assumptions...
A moderate, safe expectation for weight loss is about 1 pound per day. Now it's become more clear that either severe feed restriction OR feed restriction + increased activity level is needed for this rate of weight loss.
If you choose/or are only able to restrict feed to 1.2-1.5% of body weight without additional exercise, then we can expect a slower rate of loss- more like 0.4 to 0.5 pounds per day.
With severe feed restriction and additional exercise, we could expect horses to lose up to 2 pounds per day! That rate is safe and reasonable, but it requires strong determination. Usually, a deep fear of laminitis is involved!
Let's compare the research to a few real-life scenarios...
First off, Wilma's weight loss over the last 15 days was about 20 lbs with diet and additional exercise (mostly exercise). That means she averaged 1.33 lbs lost per day. This result is closest to the results of the Garland et. al. (2023) study using feed restriction and exercise.
Tango is an Appy mare in Pennsylvania that lost 1.42 lbs per day (100 lbs lost over 70 days) on her On Course Equine Nutrition Diet Plan. I was very happy with these results and so was the owner!
Champy is a 15 year old Arab Cross in Colorado that lost 1.83 lbs per day (55 lbs in 30 days) with two major changes; a) decreased intake to 1.7% of ideal body weight and b) decreased forage caloric density according to the On Course Equine Nutrition Diet Plan. These results are more similar to the Dugdale et. al. (2010) study, but substitute exercise with forage quality (Relative Feed Value).
We've got three very different set of conditions here which all illustrate safe and reasonable rate of weight loss over time. Each situation uses a different combination of feed restriction, forage quality, and exercise.
WILMA'S WEIGHT LOSS JOURNEY CONTINUES...
If you haven't read Parts 1, 2 or 3, I'm going to link them here...
I also want to link an article about The Equestrian App [LINK HERE] which I've been using to digitally and visually track Wilma's weight. I absolutely LOVE this app. It has a weight tracker function for subscribers- *see screenshot below. I've also used it to journal her farrier appointments, vaccinations, dewormings, tack changes, and all of the journal entries allow me to to add pictures too! I highly recommend this app to anyone.
Oh and sorry, but there's one more thing that I want to share with you! I've been using the updated Purina Weight tapes to estimate Wilma's weight each month. On October 22nd, this particular weight tape registered 1,430 lbs. Later that day, Wilma went to the vet office for a dental, and the scale registered 1,440 lbs- only 10 lbs off! The second horse that I had that day registered only a two pound difference between the weight tape and the scale. These Purina weight tapes are incredibly accurate for larger horses (>1,200 lbs), so if you have big horses and you can snag one of these at an event or from your local rep- DO IT! Unfortunately, they are not sold online. They are, however, included in the OCEN "Stop Guessing and Start Gloating" Care Package- *see image below.
REFERENCES
Dugdale, A.H.A., G.C. Curtis, P, Cripps, P.A. Harris, C. McG Argo. 2010. Effect of dietary restriction on body condition, composition, and welfare of overweight and obese pony mares. Equine Veterinary Journal. Volume 43(1):121-122.
Garland, A., D.A. Van Doorn, R. Van Den Boom, E. Roelfsema, P. McCrae, M. Boast, L. Jung, and W. Pearson. 2023. 32 Exercise versus feed restriction: What is the most efficient weight loss option for your fat horse? Journal of Equine Veterinary Science,
Volume 124.
Gill, J.C., S.E. Pratt-Phillips, R. Mansmann, and P.D. Siciliano. 2016. Weight Loss Management in Client-Owned Horses. Journal of Equine Veterinary Science,
Volume 39:80-89.
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