What steps can I take to deal with my overweight horse?

Hoof Nutrition Intelligence is a twice-a-month web segment that is designed to add to the education of footcare professionals when it comes to effectively feeding the hoof. The goal of this web-exclusive feature is to zero in on specific areas of hoof nutrition and avoid broad-based articles that simply look at the overall equine feeding situation.

Below you will find Part 2 of the latest question and answer installment that you can share with your footcare clients.

Q: What steps can I take to deal with my overweight horse?

By Juliet M. Getty, Ph.D.

A: Obesity is an epidemic problem with domesticated horses. Although we most easily attribute the problem to overfeeding concentrates combined with too little exercise, the underlying cause is much less apparent. It has to do with the horse’s brain and its response to stress, such as a chronic low-grade, inflammatory stress that tells the horse that it is not safe.

Discomfort, from any source, induces a biochemical response in the brain that triggers the horse to do whatever he can to survive. Research with a variety of species has repeatedly shown that stress tells the body to hold on to fat, as the chemical changes that occur are similar to those produced during a famine. This is based on a primitive need to feel safe. Therefore, stress “tricks” the horse’s body into gaining weight just to survive.

Stress can come from many sources, such as stall confinement, isolation from buddies, sleep deprivation, change in environment, travel to strange locations, excessive training and performing, pain and illness and exposure to toxins.

The most stressful of all is not being allowed to graze on forage at all times, which is incredibly stressful. Putting the horse on a “diet” by limiting the amount of hay he can have will create a chain of chemical reactions that prevent the very outcome the “diet” was meant to ensure.

The excess body fat of obese horses promotes inflammation through its secretion of substances known as cytokines, which can damage the areas within the hypothalamus that recognize leptin. When leptin levels are high, but the brain is not responding to it, the appetite does not decrease. Instead, the horse keeps on eating, getting more obese, producing more cytokines and increasing inflammatory damage to the hypothalamus, resulting in greater leptin resistance.  

Some horses have suffered from forage restriction for so many years that their metabolic rate has become severely impaired. For these, modest, short-term weight gain can be a consequence of free-choice feeding. Be patient, as the transition can take several months. 

Give your horse time to become accustomed, both physically and psychologically — to this new way of eating. Healthy weight loss takes time. When following the steps outlined here, the large majority of horses, even those grossly overweight, will adjust, lose weight and in time, arrive at a healthy body condition.

The leptin resistant horse will, first and foremost, have excess body fat. His appetite will seem insatiable and he will rarely lift his head from eating. His metabolic rate is sluggish, causing him to pack on the pounds very easily. He is reluctant to move and his energy level is low.  

To reduce inflammation, stress reduction will calm down the cascade of hormonal events that tell the body to hoard fat. Less body fat will create fewer inflammatory substances and insulin (an inflammatory hormone) will also decline. And less inflammation will help the hypothalamus return to a normal leptin response.

Once the horse loses body fat, the brain will initially remain leptin resistant, making the horse very hungry so he could gain back all the weight. Therefore, the approach must be to heal the inflammatory signaling in the hypothalamus. To do this:

1 Never let your horse run out of forage, not even for a few minutes. Not only is free-choice forage feeding critical to your horse’s overall health, but it increases the metabolic rate. Feed appropriate hay and/or pasture that is low in calories, sugar, and starch.

2 Add a comprehensive vitamin/mineral supplement to hay-based diets. It fills in nutritional gaps and reduces overeating to simply obtain enough nutrients.  

3 Avoid processed foods. These can contain inflammatory preservatives and omega 6 fatty acids, such as from soybean and corn oils.

4 Feed whole foods free of additives and toxins. Whole foods can include non-GMO beet pulp, alfalfa, hay pellets, copra meal, split peas, hemp seeds, ground flaxseeds, chia seeds, blue-green algae, and various fruits and vegetables. Limit soybean meal, as the long-term impact of isoflavones (the phytoestrogen found in soy) on the thyroid gland is controversial.

5 Feed a variety of protein sources by mixing grasses and adding whole foods. When only one or two sources of protein are fed, the excess amino acids can be converted to glucose, potentially increasing insulin.

6 Eliminate excess sugar and starch. These include sweetened feeds, cereal grains, wheat middlings and rice bran. They raise insulin as well as triglycerides. Triglycerides can bind to leptin in the blood stream and prevent it from signaling satiety to the brain.

7 Avoid high-omega 6 oils. They are highly inflammatory (e.g., soybean, vegetable, corn, wheat germ and safflower oils).

8 Increase omega 3s. Feed ground flaxseeds or chia seeds. Fish oils can be included in cases of high levels of inflammation.

9 Add antioxidants. These include vitamins E and C, beta carotene (vitamin A), lipoic acid, grapeseed extract, green tea extract, spirulina, as well as herbs including, turmeric, boswellia and ashwagandha (which is particularly useful in combatting stress).

10 Avoid prolonged use of H2 receptor blockers and proton pump inhibitors. They can interfere with the body’s ability to absorb nutrients and create rebound acid production upon removal.

11 Add a probiotic for digestive health. Horses who graze on pasture will naturally consume a variety of microbes. Hay-based diets, however, may not offer enough microbes for proper digestion of forage. Stress can also disrupt the horse’s normal microbial flora.

12 Exercise increases insulin sensitivity and lessens inflammatory cytokines It has also been shown to directly reduce hypothalamic inflammation.

13 Limit the use of grazing muzzles, as they can defeat the purpose if they cause stress. They should be limited to no more than 3 hours per day because the digestive tract needs more forage than they allow.

14 Not all horses require them, but some feeders are designed to initially to allow for slowing down intake.

15 Keep stall confinement to a minimum, as horses who have room to roam can be as fit as those who receive daily focused exercise, and are under far less stress.

Many barn owners are reluctant to feed hay free-choice because of the apparent additional expense. But in actuality, horses who are permitted to self-regulate hay intake will eat less. It’s only when several hours lapse between feeding that they eat very quickly and consume everything in sight. 

When they get the message that hay is always available, they can walk away from it and it will still be there when they return. Only then will they eat just what their bodies need to maintain a healthy weight and actually eat less than before.

A living, healthy grass is the best whole food and grazing is the best stress reducer your horse can experience. The amount of grazing depends on your horse’s condition. Pasture can be high in sugar and starch but it can vary depending on the month, the time of day, level of rainfall, sunlight, etc.

Turn off the body’s fat-hoarding response by taking measures to reduce stress. Combine this with an anti-inflammatory diet and increased movement, and your horse’s brain will regain its ability to respond properly to leptin. Taking off weight will become much easier.

Juliet M. Getty, PhD, is an independent equine nutritionist with a wide U.S. and international following. Located in Lewisville, Texas, her research-based approach optimizes equine health by aligning physiology and instincts with correct feeding and nutrition practices.

Click here to read part 1 of the April 15, 2021 installment of Hoof Nutrition Intelligence: Do the ridges seen in a horse’s hooves have anything to do with proper nutrition? Click here to read more installments of Hoof Nutrition Intelligence.