1. Nutritional Management of
Overweight, Pasture-Fed Horses
Jennifer C. Gill
B. A. Equine Science
PhD Graduate Research Asst.
Dept. of Animal Science
Polk Hall 209, NCSU
jcgill2@ncsu.edu
610-703-7861
2. • Dr. Shannon Pratt-Phillips
– Associate Professor
– Specialization: Equine Nutrition, Exercise Physiology
• Dr. Paul Siciliano
– Professor
– Equine Nutrition, Grazing Management
• Dr. Scott Whisnant,
– Professor
– Neuroendocrinology
• Dr. Richard Mansmann, DVM
– Equine Podiatry and Rehab.
Weight loss in twenty-
four overweight client-
owned horses
Funded by NC Horse
Council
AAVN Research
Conference
Nashville, TN 2014
3. • Digestible energy intakes of thirty-five horses over a 42-d
period
• Funded by Kemin® Industries Inc. (KemTRACE)
• 2015 Equine Science Society Research Symposium
• St. Petersburg Beach, FL
• Equine Research Unit NCSU (Spring 2015)
– Pasture digestible energy intakes
• GPS and heart-rate monitors to measure energy expenditure
4. Overview
• Identifying the Overweight Horse
• Feeding for Weight Loss
• Controlling Pasture Intake in
Overweight Horses
• Special Topic: Equine Metabolic
Syndrome
5. Research
• Prevalence of obesity
• Reasons:
– Overfeeding
• Choices
• Pasture?
– Recognition
• Incremental weight gain
– Weight reduction is difficult
6. Evaluation of Body Condition Score
• An ideal body weight is
different for every horse
• 1-9 point scale
• 1 = emaciated
• 9 = obese
• Evaluation of fat deposition Henneke, 1983
7. What is a Healthy Body Condition?
BCS = 5
BCS = 3
BCS = 8
11. Excess Fat – Why is it so bad?
• Similar risks seen in humans and small animals
• Adipose (fat) tissue is an endocrine organ that
produces and regulates hormones
• Pro-inflammatory cytokines
– “the bad cell signals that cause disease”
12. http://www.mdpi.com/ijms/ijms-15-06184/article_deploy/html/images/ijms-15-06184f2-1024.png; ;
• Heightened levels, especially in horses with a history of laminitis
• The degree to which an individual, overweight horse is affected varies
– Obesity-associated inflammation is likely age dependent
• Obesity may not cause immediate complications, but may cause a decline in
health as the horse ages
Vick et al. 2007; Suagee et al.
2011; Holbrook et al. 2012;
Goer 2015
Insulin
Cortisol
Glucose
13. Why Diet?
• Maintaining health
– A better quality of life as they age
• Disease prevention
– Laminitis
– Insulin Resistance
– Obesity-related colic (lipomas)
– Arthritis and musculoskeletal injuries
• Better performance and stamina
• Thermoregulation
14. Determining Body Weight
• Large animal scale
• Weight tape
• Body measurements
– Girth circumference
– Belly circumference
– Neck crest
15. Determining Body Weight
• By calculation (Hall)
– BW (kg) = girth circumference (cm)2
×
body length (cm)/11,880
– R2
= 0.42; underestimated BW
• http://www.thehorse.com/articles/31852/adult-horse-weight-calculator
– Martinson et al. (2014)
• BW (kg) was [girth (cm)1.486 × length
(cm)0.554 × height (cm)0.599 × neck
(cm)0.173]/3,596, 3,606, and 3,441 for
Arabians, ponies, and stock horses
– R2
= 0.92; more accurate
16. Energy (Calorie) Requirements
• Nutrient Requirements for Horses - NRC 2007
– based on weight, basal metabolism, and activity level
• Idle horse
– Maintenance ± 10% based on basal metabolism and
voluntary exercise
• Performance horse
– Light Work, Moderate Work, Heavy Work
• Growing horse (< 36 months)
17. Feeding for Weight Loss
1) Reduce Feed Intake
2) Increase Energy Expenditure
18. Energetics for Weight Loss
• A 500 kg (1,100 lb) horse requires 16.65 Mcal/d to maintain its
current body weight (NRC 2007)
– 1 unit change in BCS = 16-20 kg (35.2-44 lb) BW
– 1 kg gain/loss = ~20 Mcal above/below maintenance
• A decrease in BCS from 7 to 6 involves a difference of ~ 400
Mcal total
– Reducing intake by 4 Mcal/d will take 100 d
• 12.65 Mcal/d or less (500 kg horse)
• 76% DE/calorie restriction level Mcal: Mega calories; kg =
kilograms; DE = digestible
energy; NRC 2007
19. Reducing Feed Intake
• 70 - 90% of maintenance DE requirements (calories)
• 1.25 - 1.5% BW in total DMI
1) Body weight, requirements, and nutritional analysis
2) Weigh all feeds consumed per day
3) Maintain a balanced nutritional ration for vitamins/minerals
Van Weyenberg et al. 2008; Dugdale et al.
2010; Argo et al. 2012; McGowan et al.
2013; Gill et al. 2015 (unpublished)
http://nrc88.nas.edu/nrh/
DMI: dry matter intake; DE:
digestible energy
20.
21.
22. Calorie Restriction
• Reduce Concentrates
– Feed small meals
• Grass hay
• Extruded feeds
• High fiber/fat, low starch feeds
» Hoffman et al. 2003
• Ration balancer
• Vitamin/mineral supplement
• Hay pellets or cubes
• Reduce pasture intake
• Grazing muzzle
• Time at pasture
• Dry lot (12 m x 12 m or 24 m x 24 m)
23. Going “Grain-Free”
• Reducing grain and feeding hay
– Horses are hindgut fermenters
– Possible for idle horses
– A nutritional analysis is essential
– Weigh and feed hay at the proper amount
• > 1.0% BW in forages for healthy gut
24. Hay Quality
• Choosing a lower calorie dense hay means you can
feed the same amount and achieve calorie restriction
– 2.2 Mcal/kg hay = 0.015 X 500 kg = 7.5 kg x 2.2 Mcal/kg
= 16.50 Mcal/d
– 1.7 Mcal/kg hay = 0.015 X 500 kg = 7.5 kg x 1.7 Mcal/kg
= 12.75 Mcal/d
• 16.50 vs. 12.75 Mcal/day (78% DE restriction)
25. Controlling Pasture Intake in
Overweight Horses
• Pasture is a valuable resource
• 1.5 – 2 acres per horse
• 70% of the time grazing + voluntary
activity
• Some horses can maintain BW
on pasture alone
– Depends on many factors
– Lush pasture = Obesity?
26. CAUTIONS
• Modern pasture is high in sugars: glucose, fructose,
and fructan
– Spring and late fall
• Fructan cannot be digested in the SI
– Fermentation in the LI
– Decreased cecal pH
– Possibility for colic or laminitis
SI: small intestine; LI: large intestine
27. Pasture Dry Matter Intake (DMI)
Estimates
• Horses may consume a large amount of pasture if
given the opportunity
Marlow et al. 1983; Moffett et al. 1987; Fleurance et
al. 2001; Grace et al. 2002a,b; McMenimen et al.
2003; Edouard et al. 2009; Fleurance et al. 2009;
Glunk and Siciliano 2011; Longland et al. 2011
24 hour pasture intake estimates for MATURE, IDLE HORSES
1. 20.3 g/kg LW, 97g/LW^.75 = 2.0% BW
2. 21.9±2.4 kg/d,166.2 ± 20.8g/LW^.75/d = 3.2% BW
3. 98.6g DM/kg BW^.75 = 2.0% BW
4. 15-22 gDM/kg BW = 1.8% BW
5. 2.34 kg/100 kg BW and 56.2 g/100 g DMI = 2.3% BW
(1) Dulphy et al. 1997 (mature light horses), (2) Fleurance et al.
2001 (mature, 674 kg mares), (3) Chenost and Martin-Rosset
1985 (mature light horses), (4) Marlow et al. 1983 (mature
thoroughbreds), (5) Chavez et al. 2013 (mature light breed
geldings)
2.4% BW
2.3% BW
28. 24-h Pasture Intake (calories)
• Example:
– Two 500 kg BW mature idle horses
– 5 acres of pasture
– 1,300 kg DM/acre; 2.2 Mcal DE/kg)
– DMI ~ 2.3% BW
– DE intake 25.30 Mcals/d
• > NRC (16.65) by 8.65 Mcals/d
Dulphy et al. 1997; Fleurance et al.
2001; Chenost and Martin-Rosset 1985;
Marlow et al. 1983; Chavez et al. 2013Example by Siciliano, 2012
29. Controlling Pasture Intake:
DMI Rates
• Horses increase intake rate when time
at pasture is restricted
– DMI/ h of grazing is not linear
Dowler and Siciliano 2012
DMI: dry matter
intake; h:hour
Siciliano 2013
NRC 2.0%
BW/d in
DMI
30. Potential factors that may influence
pasture intake:
• Plant chemical composition
– NDF is inversely proportional to intake
• Plant species/variety
– Selective grazers/palatability
• Horse physiological class
• Gorging behavior?
NDF: neutral
detergent fiber
32. Grazing Muzzles
• Glunk et al. (2014)
• “Interaction of Grazing Muzzle Use and Grass Species on Forage
Intake of Horses”
• Different types of grasses and pasture intake efficiency
• 30% of non-muzzled intake
• Longland et al. (2012)
• “The effect of wearing a grazing muzzle vs. not wearing a grazing
muzzle on intakes of spring, summer and autumn pastures by
ponies”
• 0.047 % BW/h
33. Conclusions for feed restriction:
• Don’t feed free-choice, round barrel hay
to overweight horses
• Don’t feed a large amount of grain
• Don’t let obese horses have 24 h access
to lush pasture
• Do utilize dry lots and exercise paddocks
• Do consult with an equine nutritionist and
your veterinarian about restricting intake
• Do use a grazing muzzle Horse.com
34. Increase Exercise
• Encourage play
• Large enclosures
• Riding
• Walking, ponying, or lunging
https://www.facebook.com/video.php?
v=820226518039218&pnref=story
http://4legsandatail.org/the-art-of-ponying
37. Management of EMS
• Consult with your veterinarian and equine nutritionist
• Endocrine blood panel (elevated insulin/Cushing’s)
• Oral or intravenous glucose tolerance test
• Reduce body weight
• Exercise as much as possible
– Increases metabolic efficiency (improvement in insulin sensitivity)
• Powell et al., (2002) “Effect of short-term exercise training on insulin sensitivity in
obese and lean mares”
• Treiber et al., (2005) “Dietary energy sources affect insulin sensitivity and B-cell
responsiveness of trained Arabian geldings during endurance exercise”
NCS: non-structural
carbohydrates
I don’t oftentimes get the opportunity to thank the people who help me on a daily basis….
Research is no good unless the veterinarians and feed companies know about it, therefore publishing is essential for any researcher.
Variables that influence intake: enclosure size? Metabolic differences between horses?
A lot of research has gone into looking at overweight body condition in the horse population nationally and around the world. It seems that the number of overweight horses are on the incline, especially in pasture-fed horses. This may be partially due to owners perception of BC (recognizing obesity), and determining an ideal plan for reducing weight (which can be very difficult to do). It is much easier to put on pounds from an owner’s standpoint than to restrict them.
Evaluation of BCS is very important in horses as a method to determine the type of feeding program your horse should be on. Whether or not to implement a diet for weight loss or weight gain.
One horse is underweight, one overweight and one ideal weight horse.
As we increase in BCS, bone structure becomes increasingly harder to see and feel.
Neck has a crest which is a sign of metabolic imbalances.
Insulin Resistance (can occur in lean and overweight horses) - Normally when eating a meal containing glucose, glucose accumulates in the blood which stimulates the release of insulin from the pancreas to encourage the removal of glucose from the bloodstream into the tissues. Once inside the cells, glucose can be put to work producing metabolic energy. For horses with persistently high glucose levels, insulin is continually released by the pancreas leading to elevated concentrations of insulin in the bloodstream.
Because obese horses have more fat cells, they produce higher amounts of cortisol which interferes with insulin signaling; cortisol is a hormone that increases the release of glucose to the bloodstream. Such an increase in blood glucose concentration also triggers insulin release from the pancreas, to facilitate movement of glucose from the blood to the tissues.
Mortality vs. morbidity. We know our horses are going to die one day, but our goal as horse owners should be to keep them as healthy as possible for as long as possible. That’s were proper nutrition and diet come in.
You might need to separate your easy keeper from your other horses when feeding or feed a different ration to your easy-keeper.
Monitor improvement in weight management or determine a starting point.
To be able to determine a safe level of restriction, body weight needs to be estimated.
Hall; Owen et al. 10,800 denominator
Martinson et al, with height and neck measurements
Compared scale vs. body measurements in over 600 horses and ponies.
Figure 2 shows a comparison of original equations by Hall (1971) and Owen et al. (2008), the same equation but with new denominators based on breed type and the new equation using height, neck and girth circumferences, body length, and a denominator based on breed type.
Feed bags make recommendations on how much of their product to feed based on this.
When attempting to loose weight, the body becomes more efficient in using energy, therefore this makes it even harder to loose weight.
Require 1.25 – 1.5 kg BW in forage/d = 7.5 kg (16.5 lbs of hay and/or pasture) or greater in a 500 kg horse.
Between 70-90% reduction in calorie intake is acceptable, however, slower rates of weight loss are generally recommended for safety reasons, especially in ponies. Hyperlipemia is characterized by excess fat mobilization from the adipose tissue that results in a high lipid concentration in the blood and can cause serious liver and kidney damage. When reducing grain bellow product recommendation, ensure that vitamins and minerals are still being met. Vitamin and mineral supplementation may be necessary for easy keepers that require less than 3 lbs of grain per day. Hay and pasture should be evaluated for nutritional content and although requirements may be met through this source, supplementation may be necessary. This is especially important for young, growing horses.
Ca:P ratio is 1.88:1
Soaked beet pulp
Enrich plus (Purina), or equivalent
Even less calories per serving – prefer pellets over powder
Soak hay pellets and cubes to prevent choke
In addition to restricting pasture intake, reducing grain and feeding hay is your best option.
A normal functioning GI tract requires long stem, high fiber forage.
Supplement with a ration balancer or vitamin/mineral
78% DE restriction; keep in mind that this would be the only source of calories this horse would be getting.
This can be determined by a hay analysis test.
~1.5 – 2 acres per horse; Horses will spend 60-70% of their time grazing; walking activity, voluntary exercise; On adequate herbage availability, some horses can maintain health and body condition on pasture alone. However, age of horse, season, species of pasture grass, pasture management practices and time grazing all need to be taken into account before choosing to supplement.
Horses are selective grazers – they select forage based on palatability. Therefore it is recommended that pastures contain only 1 to 2 species of grass for better utilization and that practices including rotational grazing be utilized to allow pastures to rest and re-grow.
Horses are very poor at controlling intake when given continuous access to good quality pasture grass.
In addition to sugar intake being problematic, DMI in horses on pasture vary but mean estimates from many studies have found that horses can consume a large amount of pasture if given the opportunity.
DE from pasture range from 1.78 – 2.74 Mcal/kg DM (Dairy One 2011). Use 2.3% of 500 kg to estimate kg forage intake, then multiply by Mcal/kg (2.2) to get Mcal intake per day.
This amount of daily DE intake exceeds that for only idle horses and those in light work. However, pasture alone may not meet the requirements for horses in moderate or heavy activity, gestating mares, breeding stallions, and growing horses will require supplemental intake for this example.
There are may factors that may influence pasture intake….
Add photo of other dry lot
Some may feel that grazing muzzles are cruel, however, when the alternative is pasture-associated laminitis, the muzzle is the more humane alternative.
exercise and social play while reducing intake
Safely and effectively reduce intake without causing stress to your horse.
2) and activity with other horses through turnout
3) May promote more activity (how much??)
4) Even 15 minutes of walking or lunging 3-4 days a week will make a difference.
Exercise improves insulin sensitivity in horses and ponies.
Fasted blood sample taken
Give 70mg/1000 lbs Karo syrup given orally
Second blood sample taken 90 minutes later (in metabolic S. horse, blood glucose remains elevated at the 90 minute mark)
Dr. Walsh
