This document discusses equine nutrition and digestive physiology. Key points include: - Horses have delicate dietary needs as herbivores with specialized digestive systems. Proper management focuses on their grazing habits and prey instincts. - Their digestive tract includes adaptations for grazing like teeth for grinding and a hindgut cecum for microbial fermentation. Dietary changes must be gradual to avoid digestive issues. - Different classes of horses like performance and breeding horses have specific nutritional needs that change with life stage, activity level, and physiological state. Proper forage and concentrate ratios along with water intake are important. - Common digestive issues relate to dietary imbalances or changes and include colic, laminitis, and deficiencies

1. Equine Nutrition
 Very delicate dietary needs
 Management needs to focus on their
digestive tract and psychology of prey
animals

2. Horse and Donkeys
Mouth- lips, tongue and teeth
- Full set of teeth, flat for grinding
- Lips- very sensitive
- Use both teeth and lips to get food
Saliva
- Produce a lot
- Lube and buffer in proximal region of
stomach

3. Digestive tract
Non-ruminant herbivore
- Designed to eat plants, ( primarily grasses)
and graze over large distances, ingesting
a wide variety of forages in small amounts
- Confined horses with limited access to
pasture, who are fed two to three times a
day must be carefully maintained to
avoid digestive problems

4. Physiology of the Equine GI
tract
 Monogastric with a functioning cecum
 The cecum with its large amount of microbial
digestion is very similar to the rumen
 Proper dental care is essential for digestion in the
horse
 The muscles of the esophagus ( cardiac sphincter)
are so strong where they meet the stomach that
vomiting or belching is almost impossible for a
horse
 Horses will also overeat due to a poorly
functioning satiety center ( they do not feel full
and stop eating)

5. Stomach
 Small as they are grazers, should eat small amounts
throughout the day
 Cardiac sphincter- is so strong that it does not
allow vomiting
 Pyloric sphincter
- Rupture of the stomach is possible
- Stress >>> no eating>>>> then overeat
- Usually eat the wrong type of feed
- Fermenting in the stomach>> lactic acid which
impairs the relaxation of the pyloric sphincter and
emptying of the stomach ( can happen when
weaning foals)

6. Small Intestine
 Responsible for the digestion of
macromolecules
 Glycemic index: determined by composition
of the diet ( grain, forage and fat) affects
glucose levels in the body
 Pre-cecal digestion
- Depends on the type of grains and how they
are processed
- If pre-cecal digestion does not occur >>>
rapid fermentation of the contents of the
cecum can lead to colic

7. Cecum
 Large because these are hind gut fermenters
 Anatomical design leads to problems in
digestion
- A blind sac which has a very high entrance
and exit
- If there is not enough water in the diet, the
cecum will become impacted
The cecum requires a very slow transition is the
diet is being changed

8. Colon
 Finishes fermentation
 Absorbs water

9. Feeding Consumption and
Slowing Consumption
 Donkey
- Do not graze as often as horses
- Very easy keepers
- Don’t need to supplement
Horses
- Very selective grazers
- Very picky eaters
- Palatability and availability important

10. Grazers
 Spend approximately 50% of the day grazing,
mostly during the daylight hours
 Time spent grazing depends on pasture
quality and amount of forage available
Slow down the consumption of concentrates to
prevent GI disturbances:
- Spread grain thinly over a large surface
- Utilize compartments in the feed box to slow
consumption
- Feed small amounts often

11. Concentrates
 Better utilized when fed about 2 hours
after roughage is fed, due to slowing of
passage through GI tract
 The conventional procedure of feeding
the concentrate with or before the hay is
likely to depress the net value of the
dietary protein

12. Water
 Aids in digestion and elimination of wastes
 Must have fresh, clean drinking water
available at all times
 Drink 10-12 gallons a day which increases
with exercise and temperature
 Pregnant mares will also need more water

13. Energy
 Allows the horse to maintain optimum body
condition for performance, reproduction and
growth
 Body condition scores are assessed to estimate if
energy levels are adequate
1. Poor 7. Fleshy
2. Very thin 8. fat
3. Thin 9. extremely fat
4. Moderately thin
5. Moderate
6. Moderately fleshy

14. Feeding Different Classes of
Horses
 Daily rations depend on a horses lifestyle
 NRC’s 2007 Nutrient Requirement of
Horses is used by veterinarians and
technicians to make feeding
recommendations to owners

15. Forages
 Very important to provide pasture and hay
Grass forages
- Are low in Ca and high in P
Legumes
- Are high in Ca and low in P
• You want to feed a combination of grass and
legumes
• Lactating or growing foals will need
additional additives to meet their specific
dietary needs

16. Forages Continued
Tall Fescue can be infected with endophytes
- Not for use in pregnant mares
Alfalfa
- A very good choice if it is affordable
- High protein
- Feed in small amounts
- Inspect for blister beetles which will be very
irritable to the horses and can lead to colic
Timothy hay is another good choice

17. Feeds for Horses
Electrolytes and Minerals
- Especially important in endurance animals
- Necessary for bursts of energy, utilizing muscle
glycogen
- Needs vary by the animal and its use
Vitamins
Biotin
- Improves hoof condition
- Is very expensive to supplement in horses

18. Feeds for Horses ( cont)
Carbohydrates
- High grain diets can predispose them to
laminitis
Protein
- Quality is most important for young animals
- Lysine is the most limiting amino acid in horse
diets ( endurance horses are not fed high-
protein diets or alfalfa hay)
Minerals ( Ca, P, Se, Cu, Zn, Na, K and Cl)
- Adjusted when changes in hay or
training/exercise

19. Feeds for Horses ( cont)
Vitamins- not required if on good quality
hay or pasture
- Supplementation of A, E and D when
green forage is lacking in the diet
- Supplementation of animals kept in stalls
and during training
- Vitamin E reduces immunosuppression
- Horses have very low levels of calcidiol

20. Early pasture season problems
 Intake is too high when horses are first put
out to pasture in the spring or if pastures
are lush and growing rapidly
 Overeating at this time can cause
diarrhea, colic and laminitis

21. Managing pasture time in
horses
 Remove horses from pasture as soon as they
have eaten the available forage
 Horses prefer younger growth because they
digest forage less efficiently than cattle
 The horses small stomach means they need
short grazing sessions at frequent intervals
 Horses spend more time walking around and
eating then cows, especially if alone

22. Pre-cecal digestion and fat
use
Processing of corn
- Whole corn undergoes little pre-cecal
digestion so when it reaches the cecum,
unprocessed, it leads to rapid fermentation
which can lead to colic and other digestive
upsets
- Ground corn is best for digestion in the horse
- Corn is referred to as a “hot feed” because it
contains so much starch

23. Oats
 Whole grain
 Good pre-cecal digestion in horses
 Additional processing is usually not an
advantage
 Crimping or micronized can decrease
pre-cecal digestibility

24. Fats
 Horses do not have a gall bladder, bile is
released directly into the digestive tract
 Fats in the diet delay gastric emptying of
carbohydrates
 Supplement fats only if exercise increases
and intake is maximal

25. Carbohydrates
 Pre-cecal digestibility determines the proportion of
cereal carbohydrates absorbed as glucose and
that absorbed as Volatile Fatty Acids and the
potential for adverse hindgut fermentation
 Pre-cecal digestibility of oat starch exceed that of
corn, barley, and sorghum
 Grinding enhances pre-cecal digestibility but
reduces shelf life of cereals
 Small intestine carbohydrate digestibility is
influenced by the type of cereal, grain processing
and amount fed

26. Carbohydrates ( cont)
 High pre-cecal digestibility decreases the amount
of lactic acid and other organic acids in the large
intestine and the problems of grain overload
 When undigested starch reaches the ileum and
cecum, organic acid production is increased and
the Ph is decreased
 Feed modification is important in nutrient
utilization but more important in preventing
hindgut problems
 This is why most horse owners prefer to feed oats
instead of corn

27. Feeding Programs for Horses
 Maintenance
 Reproduction
 Growth
 Performance
 Aging
 foals

28. Maintenance Horses
 Mature, non working horses that are not
pregnant or nursing
 May need supplements depending on
pasture and forages in the diet
 Good quality pasture in summer and hay
in winter
 Adequate forages will deter many
abnormal behaviors

29. Reproduction
 Increased Calcium and Phosphorus
 Make sure they have an acceptable body
condition score
 Gradual increase in intake around 6 months
and by 8-10 months, 20% increase
 Maintain BCS 5-7, moderate, fleshy condition
but not obese
 Ca and P needs increase in last trimester and
during lactation
 Prenatal nutrition- Cu to foal in utero reduces
DOD

30. Development Orthopedic
Disease
 The term "DOD" describes a variety of
orthopedic disorders in growing horses.
Contracted tendons, wobbles, phystis,
osteochondritis, osteochondrosis
dissecans (OCD) and angular limb
deformities are all considered
Development Orthopedic Disease.

31. Growth
 Critical in avoiding DOD
 Use of creep feed
 Accelerated is bad for bone and joint
formation

32. Performance
 Anaerobic activity- build up reserves of
glycogen for easily accessible energy
 Aerobic- utilizes fatty acids and stores
glycogen
 Ergogenic aids
- Additives
- Metabolites
- Enhances performance
- Sodium bicarb milkshake prevents lactic acid
build up, given before the race BANNED

33. Aging Horses
 Small amounts at a time of a highly
digestible feed
 Teeth are extremely important, owner
must pay attention to them
 Senior pelleted diets are complete but for
optimum GI health, they need forages

34. Breeding Meet the requirement of the mare and the
foal
 Nutritional needs change during gestation
 Early gestation, late gestation or lactation
 Body condition scoring is essential
 First 8 months of gestation nutritional
requirements are similar to maintenance
 Last 3-4 months of pregnancy must increase
protein, energy, vitamins and minerals
 Foaling/lactation consume between 2-3 % of
body weight

35. Stallion Nutrition
 Maintenance until breeding season
( protein requirements are higher than
mare maintenance)
 Assess body condition prior to breeding
season
 Thin stallions can have reduced libido and
fertility

36. Aged Horse Nutrition
 Genetics and lifestyle determine when a
horse is classified as aged
 Many older horses have dental problems
which can lead to severe nutritional
problems
 Motility of the digestive tract can also
decrease with age
 Processed feeds may lead to better
absorption

37. Normal Foal Nutrition
 Must receive colostrum within the first 18 hours
of birth
 May need an enema to pass meconium
 The mares diet should provide all the required
nutrients so her milk will lead to optimal
growth in the foal
 Coprophagy will actually benefit the foal by
providing the GI tract with necessary
microbes
 Orphan foals need a nurse mare, nurse goat
or milk replacer

38. Coprophagy
 Normal foal behavior, possibly due to
pheromones, it should not be
discouraged
 Innoculates the GI tract with necessary
bacteria, and vitamins
 Starts as early as the first week of life,
especially during the first two months,
utilizing the feces of the mare

39. Nutritional supplements for
foals
 If foals are unable to feed, they must be
supported by enteral or parenteral feeding
 Delayed feeding of the foal can lead to
problems
- won’t get colostrum which is necessary for the
foals immune system
- Reduction in intestinal villi height
- Decreased weight of stomach, pancreas and
small intestine
- Increased risk of necrotizing entercolitis

40. DOD
 Alters growth rate
 Copper is involved in the cross linking of
matix
 Growth plate is a very active region
 Ca:P ratio needs to be correct

41. Donkey Feeding and Nutrition
 Higher forage digestibility
 Very adaptable, easy keeper
 Energy- low resting metabolism
 Can utilize straw
 Water- don’t need to drink as much because they
don’t waste as much energy, and don’t sweat as
much
 Major problems: over feeding leading to obesity
 Like short grass
 Utilize protein very efficiently

42. Laminitis Founder or lameness, especially of the forefeet
- Genetic differences in susceptibility
- Exposure to black walnut
• Inflammation of the sensitive laminae of hoof
• Nutritional etiology- carbohydrate overload of
hindgut
- Grain or lush pasture ( overloading)
- Grain with low pre-cecal digestibility
* Microbial growth increases lactate and microbial
toxins

43. Laminitis ( con’t)
 Preventative nutritional intervention includes:
- Avoid sudden exposure to lush pasture or
grain
- Maintain susceptible animals on dry feed
such as grass hay
- If grain mix is used, factor in pre-cecal
digestibility and glycemic index
- If grain is fed, feed using Virginiamycin as an
additive

44. Azoturia Characterized by dark, sweet-smelling urine,
myoglobinuria, severe muscle cramping
( tying up), animal is stiff and sore and in great
pain
 A genetic condition may predispose horses to
this condition ( improper use of glycogen)
 Associated with hard exercise and forced
immobility
 Vit E and Se deficiency and electrolyte
imbalance may predispose horses to it

45. Azoturia nutritional intervention
 Feed balanced ration in small meals to
avoid excess glycogen storage
 Feed a low – energy diet with added fat
and avoid grain
 Feed high-quality alfalfa hay but make
sure to balance for Ca and P

46. Starvation and Neglect
 Detrimental effects on the immune system,
digestive tract health, healing and body score
Feeding a starved, neglected horse ( Stull, 2003)
1. Days 1-3 one pound of leafy alfalfa every 4 hours
2. Days 4-10 increase amount of alfalfa to four
pounds every 8 hours by day 6
3. Day 10 to several months feed as much alfalfa as
the horse will eat twice a day. Provide a salt block.
Do not feed grains or supplements until the horse
maintains a normal body score

47. Colic
 Generic term for abdominal pain caused by
distension of the gastrointestinal tract
 Many causes of colic are related to the diet
 Impaction
- Due to reduced water intake
- Poorly digestible feeds
- Ingestion of sand
- Sudden diet changes
- Poisonous plants

48. Colic ( cont)
 Gas- from fermentation
- Consumption of lush green forage or grain
- Sudden change to a much lower nutritional
plane
• Irritation of gastrointestinal tract or alteration
of motility
- Poisonous plants
- Blister beetles in hay

49. Possible Causes of Colic
 Feeding unwholesome feeds
 Horses bolt their feed
 Overfeeding
 Irregular feeding schedule
 One large meal per day
 Diet changes without a transition period
 Inability to vomit

50. Vitamin deficiencies
 Se and Vit E
- White muscle disease and steatitis in foals
- Reproductive failure and azoturia in
adults
- Equine motor neuron disease due to low
plasma vit E
White Muscle Disease
- stiff, stilted gait, hopping in rear legs
- Necropsy shows mottled white patches of
gritty feeling muscle

51. Vitamin Def ( cont)
 Selenium deficiency
- In presence of adequate vitamin E
- Generalized steatitis
- Subcutaneaous fat is grossly tan and appears
necrotic
• Biotin deficiency
- Hoof wall problems
- Low in grains
- corn and soybean meal> oats> wheat, barley and
milo
- Bacteria in gut generates avidin which binds biotin

52. Horse Feeding Wrap up
 Keep feed boxes clean
 Make feed changes, especially
carbohydrates gradually
 Feed frequently
 Feed at the same time of day
 Feed by weight, not volume
 Slow horses that bolt food by spreading feed
out
 Check teeth regularly
 Have fresh water available at all times