1. My Horse University and eXtension’s HorseQuest
welcome you to this live Webcast.
Digestive Anatomy:
Why We Feed Horses the
Way We Do
Dr. Carey Williams
Rutgers University

2. Meet our presenter:
Dr. Carey Williams
Rutgers University
Question facilitator: Danielle Smarsh, Doctoral Candidate
Rutgers University

4. FOREGUT:
• Mouth
• Stomach
• Esophagus
• Small Intestine
HINDGUT:
• Cecum
• Large Colon
• Small Colon
• Rectum

5. Mouth
• Function:
– Selection
– Chewing
– Saliva
– Swallowing
• Teeth:
– Incisors: shear forage
– Molars: grind food

6. Teeth Floating
(Hill, 1997. Horse Health Care)

7. Choke
Endoscopy of
an esophageal
obstruction

8. Stomach
• Small stomach capacity, only 2-4 gallons for a
1100 lb horse
– Secretes HCl and Pepsin to begin the breakdown
of food
– Unable to regurgitate food
• Sphincter between esophagus and stomach only allows
passage of food one way
• Horses Can’t Throw Up!

9. Small Intestine
• Small intestine is 50-70 ft long and holds 10-
23 gallons
– Most of the nutrients (protein, some CHO and fat)
are digested here
– Most of the vitamins and mineral are absorbed
here
– Water is not absorbed here but helps move the
food through

10. Accessory Organs
• Pancreas:
– Production/secretion of pancreatic juices for
protein, starch, fiber digestion
• Liver:
– Production of bile
– Emulsification of fat
– Bile secreted continuously by the liver
– NO GALL BLADDER!

11. Large Intestine
• Large Intestine:
• Cecum
• Large and Small colon
• Rectum
– Forage fermentation
– Water absorption

12. Cecum
• Liquids are passed to the cecum
– 3-4 ft long and holds 7-8 gallons
– No detoxification of toxic substances until they
reach the cecum
– Contains bacteria to
digest the fiber and some
carbohydrates

13. Cecum
• Functions:
– Microbial Fermentation:
• Volatile fatty acids: acetic, propionic, butyric
• B-Vitamins, Vitamin K, Gas
– Absorption:
• Protein and fermentation products
• Transit time:
– Slow- 38 to 48 h
– Liquids- 5 h

14. Microbial Digestion
Microbes
Fiber from
forage &
other
undigested
residuals
VFA’s, B-vitamins,
Vitamin K, Gas

15. Avoid Abrupt Changes

16. Large Colon
• Large colon is 10-12 ft. long and holds 14-16
gallons
– Four parts:
• right ventral colon
• sternal flexure to left ventral colon
• pelvic flexure to left dorsal colon
• diaphragmatic flexure to the right dorsal colon
– Sternal and diaphragmatic flexures are a common
place for impaction

17. Large Colon

18. Small Colon
• Small colon leads up to the rectum
– It is 10 ft long and only holds 5 gallons
– Smaller diameter than large colon
– Functions:
• Water absorption
• Formation of fecal balls
• Rectum 1 ft in length
– Function: Storage reservoir

19. Nutrients
Site of: Digestion Absorption
Water ------- Colon
Protein Stomach & SI SI
Lipid SI SI
CHO's
Simple SI SI
Complex
Starch SI SI
Structural LI LI

20. Monogastrics
Mouth
Stomach Protein digestion
SI Prot absorption, lipid dig/absorp,
Simple CHO dig/absorp
Cecum Complex CHO fermentation
Colon Complex CHO fermentation
Absorption of water

21. Grains and Forages for
Horses

22. Roughages vs. Concentrates
Roughage Concentrate
Fiber High Low
Energy Low High
Protein Variable Variable
Cost Lower Variable
Density Low (bulky) High

23. Roughage
• Pasture and Hay:
• Horses should consume AT LEAST 1 % of their
BW per day
– 1000 lb horse = 10 lb hay
• Nutrient intake depends on forage quality
• Feeding quality forage can reduce cost of
feeding grain

24. Pasture
• Grasses:
• Cool season:
– bluegrass
– orchardgrass
– timothy
– tall fescue Timothy Orchardgrass
• Warm season:
– bermuda
– bluestem
– sudan

25. Pasture
Legumes:
• Alfalfa
• Clover

26. Hay
• Hay:
• Grasses and legumes are
cut to make hay
• Orchardgrass/Alfalfa
• Legumes have higher:
• protein
• energy
• TDN
• COST!

27. Hay Quality
• Never feed dusty or moldy hay!
• Quality depends on:
– Plant Maturity
• No seed heads
– Leafiness
• Smaller stem size
– Smell
– Color
– Weeds/Debris

28. Hay Guidelines
• Hay requirement:
– Feed at least 50 % of the total ration as forage
(pasture and/or hay)
• E.g. 1000 lb horse will eat 15 to 30 lb of food
• If feeding 20 lb; at least 10 lb should be forage
– High quality grass hay or alfalfa/grass mix
– Caution with straight Alfalfa
• Creates Ca:P ratio imbalance
• Diet too high in protein

29. Concentrates
• Grains:
• Fiber - low (2 -10%)
• Energy - high
• Protein - low (8 to 10%)
• Cost - reasonable
– Examples
• Corn
• Oats
• Barley
• Sorghum

30. - most popular
OATS - lower energy value
CORN
- higher fiber
- more palatable and
digestible
- can be expensive
- palatable
- 2 x energy as oats
- low in fiber
- mostly for humans - small hard kernel - easy to over feed
- expensive - not palatable - moldy is lethal
- small hard kernels - used in grain
- high energy mixes - high energy - hard hulls
- low palatability - low fiber - medium fiber &
energy
WHEAT MILO BARLEY

31. - byproduct of grain processing
is oil
- 35 % protein
- 85 % is digestible
FLAXSEED
RYE
- high-energy ingredient
- usually as part of a mixture
- kernel has high nutritional
value
- the plant itself is a good
roughage source

32. Feeding Guidelines
• Forage is the base
– Always try to feed the most forage possible
• Feed about 2% of the horses BW
– 1000 lb horse = 20 lb
• Feeding a 1000 lb horse at maintenance:
– If 5-6 lbs grain;
– then no less than 15 lbs of hay

33. Feeding Guidelines
• Horses should be fed to meet their immediate
needs
– I.e. cut grain on rest days
• Horses’ stomachs are small so feed at least 2 x
a day
– More times a day the better

34. Feeding Guidelines
• Feed by weight not volume!
– 1 lb oats is not 1 lb of corn
• Monitor condition scores
– Score of 5 is appropriate

35. Feeding Guidelines
• Store feed properly, no mold or rodent
contamination
• Feed on a set schedule
– Horses are creatures of habit
– They easily upset by changes in routine
• Change feeds gradually
– Horses stomachs cannot cope with drastic change
– It upsets the microbes in the GI tract causing colic

36. Feeding Guidelines
• Be aware of the pecking order
– Are they getting their food?
• Regularly de-worm
– Most common cause of a thin horse
• Regularly examine teeth
– Can they chew food?
• Feed off the ground in hay racks or tubs
– Prevents dust inhalation

37. Thank You!
Carey Williams, Ph.D.
Equine Extension Specialist
cwilliams@aesop.rutgers.edu
www.esc.rutgers.edu
Equine Science Center
Better horse care through research & education

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39. Upcoming Webcasts
• Protein Requirements for Horses
October 23, 2012 | 7PM EDT
• Equine Energetics
November 27, 2012 | 7PM EDT

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