Equine Nutrition & Feeding
Peggy M. Auwerda
Time-Budgets
Feral Horses
Select highest fiber,
lowest protein content
70% of its day foraging
Stabled Horses
10% of their day feeding
Meal fed
Digestive Tract
The Mouth- first part
of digestive system.
Mouth has 2 main
functions- masticate
food and wet food
with saliva.
Mastication
•Jaw sweeps 60,000
times/day when grazing
•Saliva contains little, if
any amylase
Digestive Tract
Stomach –
9-15 liters
Trickle feeders
Transit time <2 hr
Cardiac sphincter
does not relax to
allow regurgitation
Digestive Tract
Small Intestine
30% of digestive tract
40-50 liters
Transit time – 45 min to 8 hrs
α-Amylase – low & varies widely
between horses
Starch digestion occurs in the
stomach and small intestines
Amino acids and fat digested
and absorbed in small intestine
Vitamins/minerals absorbed in
small intestine
Digestive Tract
Hindgut – 60% of digestive tract
capacity
Cecum –
25-35 liters
Transit time < 5 hr
Large Colon
50-60 liters
Small Colon
18-19 liters
Large & small colon transit
time 48-72 hours
Fiber digesters most active
pH of 6.2-6.8
Starch digesters prefer pH 5.2
– 6.0
Aspects of The Foal GI Tract
Small digestive tract
The small intestine does not
increase in length from 4
wks of age
Cecum not fully functional
until 15-24 mo of age
The large intestine
increases with age even up
to 20 yrs
Microbial Fermentation
Volatile
Fatty Acids
Microbe
Fibrous &
Non-Fibrous
Carbohydrate
Gas
Metabolized
For
Energy
Wasted
Energy
B-vitamins & Vit. K
Protein and Amino Acids?
Starch
Starch is an
important and
valuable
component of the
equine diet.
Equine athletes
need
carbohydrates for
efficient energy
use.
Mares need
carbohydrates
to help
produce
healthy foals.
Mares need
carbohydrates
for milk
production.
Comparison of Corn and Oats
%
90
80
70
60
50
40
30
20
10
0
Corn
Oats
Starch
Fats
Protein
Small
Large
Intestine Intestine
Digestion Digestion
Postprandial Cecal pH
Change
7.6
7.4
7.2
Oats
Corn
Hay
7
6.8
6.6
2
3
4
5
6
7
Starch Overload
Starch not digested in SI is delivered to hindgut
for bacterial fermentation. Too much starch may…
Cause radical changes to hindgut flora
Increase VFA & lactic acid concentrations – hindgut
acidosis
Cause laminitis, colic, endotoxemia, metabolic acidosis,
behavioral problems (wood chewing)
Critical capacity for hydrolysable
carbohydrate overload ~0.4% of BW
Cuddeford, D. 1999; Harris et al. 1999
How hindgut acidosis can occur in hindgut and how it can be attenuated
High Grain or
High Fructans
Increase in VFA&
Lactic Acid of
Hindgut
Time Released
Buffer
Minimal decrease
in pH
Optimal VFA
absorption
Optimal Energy for
Working & Breeding Horses
Significant decrease
In pH
Decrease in fiber fermenting Organisms
Increase in lactate producing organisms
Very low pH
Bacterial lyses
Release of
endotoxins
Laminitis
Subclinical
Acidosis
Irritation & damage
To intestinal mucosa
Inhibition of fiber fermenting
Organisms & lactate
Utilizing organisms
Off Feed
Decreased fiber
digestibility
Colic Symptoms
Stereotypic Behaviors
Pagan, J. 2007. Feedstuffs
Carbohydrates
Total CHO
Non-Fiber
Carbohydrates
Nonstructural
Carbohydrates
Neutral Detergent
Fiber
Neutral Detergent
Soluble Fiber
Hemicellulose
Acid Detergent
Fiber
Sugars
Pectins
Cellulose
Starches
Fructans
Lignin
β-Glucans
Starch Comparisons (what’s low, what’s high)
Ingredient
NSC
% DM
Sugar
Starch
Pectins
Beta-Glucans
-------------------------- % of NSC ---------------------
Alfalfa hay
23.0
0.0
40.9
33.0
Grass hay
17.2
35.4
15.2
49.4
Barley
61.8
9.1
81.7
9.2
Corn
71.4
20.0
80.0
0.0
Oats
42.4
4.4
95.6
0.0
Wheat
73.8
8.9
80.2
10.9
Distillers
10.3
0.0
100.0
0.0
Corn gluten feed
24.7
3.7
71.2
25.1
Corn gluten meal
17.3
0.0
69.4
30.6
Soyhulls
14.1
18.8
18.8
62.4
Soybean meal, 44%
34.4
25.0
25.0
50.0
Wheat midds
31.2
10.0
90.0
0.0
Methods Of Maximizing Starch
Digestion In Small Intestine
Properties of the starch granule
Grain processing
Plant cell walls
Transit time through the small
intestine
Availability & concentration of
enzymes
REMEMBER!
“The number one cause of deaths from
colic is from starch overload due to
feeding mismanagement.”
Dr. John Reagor, PhD
Chief of Toxicology
Texas Veterinary Medical
Diagnostic Laboratory
Glycemic Response
 Hyperglycemia occurs after
digestion of grain meals
 Affects substrates utilized
during exercise
 Glucose & insulin peak 60-90
min after a meal
 Insulin promotes fat storage
 Sugary meals before exercise
will  CHO to muscle & ↓ fat
oxidation
Feeding Horses
 Feed intake usually expressed as
 % of Body Weight
 Lbs feed/100 lbs body weight
 Free Choice
Forages – Maximize in the ration
Provide fiber & energy
Min. at least 1% of body weight (dm basis)
Concentrates
Provide energy
Supplements
Provide protein, minerals and vitamins
Estimating Weight (lbs)
Heartgirth (in) x Heartgirth (in) x Body Length (in)
330
Energy
Determines Weight & Condition Of Horse
Body Condition Score
Measures amount of
body fat (1-9 scale)
Determines balance
between energy intake
& expenditure
Simple, repeatable,
consistent method
Comparison between
animals
Body Condition Score
Fat laid down in
predictable patterns
Organs
Behind the shoulder
Ribs
Rump
Back
Withers
Head and Neck
Body Condition Score
Evaluation
Visual assessment and
actual touch
Palpate fat areas
Avoid mistaking longer
hair covering for fat
areas
Avoid being fooled by
conformation differences
Body Condition Scoring
1-3 Poor-Thin
4
Can see ribs,
vertebra ridge evident
5 Back flat, can’t see
ribs, but can feel them
6 Crease down back, fat
deposits
7-9 Fleshy - Extremely fat
Time & Additional Grain
Required To Improve
BCS by 1 level
Improving 1 Condition Score
Days Needed
Daily Gain
60
0.75 lbs/day
Additional Grain
Needed
4.5 lbs/day
90
0.50 lbs/day
3.0 lbs/day
120
0.40 lbs/day
2.3 lbs/day
Optimum Body Condition Score
Each horse has its own ideal condition
for the breed & use
Average horse
Broodmare
Breeding stallion
Performance horse
5-6
5-7
5-6
4-6
Building a Horse Ration
Start with horse needs
Maximize forage
Add energy if needed
Add protein & minerals if needed
Consider adding vitamins &
supplements
Consistency is key to good
feeding practices
Feed concentrate that makes-up the difference between nutrients
needed & nutrients in roughage
Forages are the Foundation
Pasture, Hay
Grass
Bromegrass
Orchardgrass
Tall Fescue
Timothy
Grain Hay
Oat Hay
Wheat hay
Straw
Legume
Alfalfa
Birds Foot trefoil
Clovers
Lespedeza
Ingredients Used In Place of Hay for
Roughage
Good Quality
Sources:
Beet Pulp
Soybean Hulls
Dried Citrus Pulp
Dried Apple Pectin
Pulp
Alfalfa Meal
Poor Quality
Sources:
Peanut Hulls
Oat Hulls
Ground Straw
Cottonseed Hulls
Rice Hulls
Rice Mill Feed
Forage Isn’t Everything
Most do not have all the minerals &/or
vitamins a horse requires. Four ways to
add these.
1. Add 1 to 4 oz mineral or mineral/vitamin
supplement per day or
2. Add 1 to 2 lbs ration balancer (mineral plus
protein) per day or
3. Feed 5 to 7 lbs fortified grain per day or
4. Feed 12 – 14 lbs complete feed (forage & grain)
Energy Sources - Grains
Oats
Barley
variable
crimped vs. whole
Corn
cracked, steam rolled
Sorghum & wheat
less than 30%
rolled, cracked, flaked,
Fat/Fatty Acids
• No gall bladder
Horses can be safely fed up
to 20% fat in the total diet
Energy from fat is 90%
utilizable
Often used to supplement
calories for hard-working
horses and hard keepers
 Reduction in DM intake &
bowel weight
 Calmer temperament
Protein
Muscle & bone growth,
milk production, fetal
growth, normal
metabolism
Most horses
requirements can be met
with good quality hay or
pasture forage
Protein
Quantity = amount
Quality = amino acid balance
Very important for young
horses
Lysine, methionine,
tryptophan most limiting
for growth & milk
production
Sources of Protein for Horses
Soybean Oil Meal
Flax - Linseed
Meal
Sunflower Meal
Cottonseed Meal
Peanut Meal
Corn Gluten Meal
Whey
Dried Skim Milk
Minerals
Content in the diet
Determined by soil & water
Quality of feed & proportion of grain to hay
Macro-minerals
Ca & P - quality forages usually provide adequate amount
This ratio is very important: 1.5:1 to 2:1
Grains are rich in P and low in Ca
NaCl (Salt)
Salt block will meet many horse’s needs
If horses sweat a lot - need salt in the ration
Trace Minerals
Look for iron, zinc, copper, selenium
Minerals
Macro-minerals
–
–
–
Ca & P - quality forages usually
provide adequate amount
This ratio is very important:
1.5:1 to 2:1
Grains are rich in P and low in
Ca
NaCl (Salt)
Salt block will meet many
horse’s needs
If horses sweat a lot - need
salt in the ration
Trace Minerals
Look for iron, zinc, copper,
selenium
A guide to the
recommended
concentrations of
trace elements in
the diet, mg/kg dry
matter. (Modified
from
the NRC 2007).
These will need to
be adjusted to suit
individual
circumstances,
growth rate and
appetite etc.
Vitamins
Fat soluble:
- stored in body - A, D, E, K
- Toxicity’s can occur if fed in excess
Water soluble:
- must be continuously supplied
- B-complex; niacin, thiamin, riboflavin
Vitamins
High quality fresh forages =
maintenance for mature horses
Hay is poor in Vitamin A
Supplement Vitamin A in the ration
Exposure to sunlight provides Vitamin D
Guide to recommended levels of Fat-soluble vitamins
(need to be adjusted according to individual
circumstances).
Nutrient Requirement Varies With
Class of Horse – NRC 2007
Adult (no work)
Working
Light exercise
Moderate exercise
Heavy exercise
Very heavy exercise
Stallions
Pregnant Mares
< 5 mo
5th, 6th, 7th, 8th, 9th, 10th,
11th mo
Lactation
1st, 2nd, 3rd, 4th, 5th, 6th mo
Growing
4, 6, 12 mo
18 mo
Light exercise
Moderate exercise
24 mo
Light exercise
Moderate exercise
Heavy exercise
Very heavy exercise
Water
Essential for all body functions
Temperature regulation
Feed digestion
Amount of water intake
Level of exercise
Ambient temperature
Quality of feeds in ration
Proportion of diet that is forage
Minimum 1 gallon/100 lbs BW/day
Maintenance
Size: body weight
Environment
Individual
differences
Dry matter intake:
1.5% of the BW
Most - energy
requirements are
met with forage
alone
Recommended Daily Feed Intakes as
% of Body Weights
Class
Forage
Concentrate
Total
Example
1,000 lb
horse
Mature (Idle)
1.5 - 2.0
0.0 - 0.5
1.5 - 2.0
15-20 lb
Geriatric
0.8 – 2.0
0.5 – 2.0
1.5 – 3.0
15-30 lb
Geriatric Horses
Nutrient Considerations
Reduced salivation
CF digestibility ↓
Total fiber < 30%
CP digestibility ↓
10-14% CP
Energy:
Increase soluble carbohydrates,
fats, & oils
Caloric Restrictions
Supplement minerals & vitamins including
vitamin C
28 yr old horse
Selection of Feed For the
Geriatric Horse
Highly palatable
Easy to chew & swallow
Forage - chopped, cubed,
pelletized, or in a wafer
Grains - rolled, crimped, or
flaked
32 yr old horse
Feeding The Athlete
Aerobic and Anaerobic Metabolism
During exercise, ATP is generated from
breakdown of:
Glucose
Fatty acids
Amino acids
ATP low in muscles; essentially no storage
Continuous ATP production vital for athletes
Simplified Energy for Muscle Contraction
Blood Glucose
Free Fatty Acids
Lipolysis
Muscle Glycogen
Lactate
Creatine
Phosphate
Pyruvate
ATP
Oxidative
Metabolism
CO2and
Water
O2
Work
ENERGY, ENERGY, ENERGY!
Levels of Performance/Work
 Light – Recreational riding, beginning of
training programs, Show horses
(occasional)
 Moderate – School horses, Recreational
riding, Show horses (frequent), Polo, Ranch
 Heavy– Ranch, Polo, Show horses
(frequent, strenuous events), Low-medium
eventing, Race training (middle stages)
 Very Heavy – Racing, Elite 3-day event
Performance/Work
Energy =
Activity
Maintenance
DE (Mcal/d)
16
Light
20.0
Moderate
23.3
Heavy
26.6
Very Heavy
34.5
Feeding Guidelines for
Performance Horses
Starch is necessary for replacing glycogen stores.
Hay
Feed at least 50% of total ration as forage (pasture &/or hay)
Preferably high quality grass hay or alfalfa/grass mix
Exercising horses do not need high levels of protein
More important – quality of protein
Horses should be fed to meet their immediate needs
Cut grain on rest days
FAT SUPPLEMENTATION
 Enhanced stamina
  capacity for uptake & oxidation
of fatty acids in muscle
 Concomitant decrease in use of
endogenous carbohydrate stores Muscle glycogen sparing
Add 6-10 weeks before performance
Feeding Guidelines for
Performance Horses
Hay requirement
Feed at least 50% of total ration
as forage (pasture &/or hay)
Preferably high quality grass hay
or alfalfa/grass mix
Exercising horses do not need high
levels of protein
More important – quality of
protein
Horses should be fed to meet their
immediate needs
Cut grain on rest days
Breeding Animals
Maiden mare
Barren mare
Flushing- Increasing
energy intake 2025% ~3 wks prior to
breeding.
Gestating mare
Lactating mare
Stallion
Gestating Mares
•Last 3 month of gestation: 60 % foals’ weight
•Mare needs to gain 0.3 – 0.8 lb/d
Lactating Mare
Lactating Mare
milk is 3 % BW
Month 4 – 6 =
milk is 2 % BW
Requirements of
energy, protein,
mineral, and vitamin
double vs.
maintenance
Daily Milk Production (lbs)
Month 1 – 3 =
28
27
26
25
24
23
22
21
15
30
45
60
Time (days)
90
120
150
Feed Consumption (% BW)
Mare status
Forage
Concentrate
Total
Early pregnancy
1.5-2.0
0-0.5
1.5-2.0
Late pregnancy
1.0-1.5
0.5-1.0
1.5-2.0
Early lactation
1.0-2.0
1.0-2.0
2.0-3.0
Late lactation
1.0-2.0
0.5-1.5
2.0-2.5
•Adding concentrate to late pregnancy mares accounts for limited energy & acclimates
microbes
•Allow 1 wk to 10 d for mares to adjust to intake changes
•Heavy milkers may require as much as 1.75-2.0% of BW in concentrate feed/day
Body Condition Score
Maximum Reproductive Efficiency
Moderately fleshy to fat mares can
be expected to
Cycle earlier in the year
Have fewer cycles per
conception
Have a higher pregnancy rate
Maintain pregnancy more easily
Mare prior to breeding should have
a BCS of 6 or greater and fed to
maintain weight.
BCS of 5.0 is marginal especially
for lactating mare.
Feeding The Growing Horse
Goals
Maximize genetic
potential for
growth
Sound
musculoskeletal
system
•Nutrient Balance is important
•Requires higher quality feeds
•Growth rate & age determines requirements
•Growing till reach 30 months
Average Daily Gain
3.5
3
2.5
2
1.5
1
0.5
0
0
2
4
6
8
10 12 14 16 18 20 22 24
Month of Age
Nutritional Strategies Aimed at Minimizing DOD
Rations
should be
balanced to
promote a
consistent
growth
curve
Requires
periodic
updating
of the
ration
www.Foalcare.com
Nutritional Strategies Aimed at Minimizing DOD
Feed selection
High quality forage is a must
Grain mix concentrates formulated specifically for growing
horses
Improper use of supplements
Feed amounts
Forage
Minimum of 1 lb / 100 lb BW / d
Fed to appetite is best
Concentrate
~ 1 lb / 100 lb BW / d
Max. 8 to 10 lbs /d
Monitor The Growth
Process
Daily Intakes
Body Weight
Average daily gain
Signs of Skeletal Abnormalities
Physitis
Joint effusion
Lameness
Feeding Guidelines & Strategies To Minimize
Risk Of Hind Gut Dysfunction
Know Your Horse
& Provide Feed Based on:
Class
Stage of production
Age
Activity level
Growth
Feeding Guidelines & Strategies To Minimize Risk
Of Hind Gut Dysfunction
Consider..
Quality of feeds
available
Body Condition
Feeding Guidelines & Strategies To
Minimize Risk Of Hind Gut Dysfunction



Check for Refusals
Change type &
amount of feed
gradually. 7-10 d
period
Provide Salt
Feeding Guidelines &
Strategies To Minimize Risk
Of Hind Gut Dysfunction
Control amount of NSC (sugar, starch & fructan) the horse
consumes.
Minimize the flow of fermentable polysaccharide to the
large intestine
Feed starch sources little and often i.e., less than 5g
oats/(2g starch)/kg body weight/meal
Pre-feed forages
Feeding Guidelines &
Strategies To Minimize Risk
Of Hind Gut Dysfunction
Minimize the flow of fermentable
polysaccharide to the large intestine
Limit rate of concentrate intake
through physical obstruction
Maximize substrate (glucose)
availability to the performance
horse
Ensure good occlusion of teeth
through regular dentistry
Feeding Guidelines & Strategies To Minimize
Risk Of Hind Gut Dysfunction


Group Feeding Should
Account for Dominance
Hierarchies
Recognize Feeding-Related
Behavior Problems
REINS
Relevant Equine Intensive
Nutrition Software
Peggy Auwerda & Garland Dahke
REINS
Total mixed ration (TMR)
program that allows for
evaluation and formulation of
protein, energy, vitamin and
mineral requirements of horse
rations across multiple stages
of production
Based off of the 2007 NRC
Nutrient Requirements of
Horses
Written in MS Visual Basic and
uses MS Excel as the user’s
interface to operate
REINS
Least cost formulator can
be used or rations can be
entered manually
Extensive feed library –
Up to 220 feeds
Multiple feed libraries can
be created which allows a
use to assign a feed
library to a farm
Comprehensive
appendixes