This document discusses equine nutrition and digestive physiology. Key points include: - Horses are hindgut fermenters with a large cecum that requires a slow transition between diets. Improper feeding can cause digestive issues like colic. - Proper dental care, grazing time, and small frequent meals are important for digestion. Changes should be gradual to avoid problems. - Nutritional needs vary depending on a horse's life stage, from foals to aging horses. Macronutrients, vitamins, and minerals must be balanced accordingly. - Feeding management can help prevent conditions like laminitis, azoturia, and deficiencies. Sudden diet changes or neglect can compromise a horse's

1. Equine Nutrition

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