Equine Nutrition Very delicate dietary needs Management needs to focus on their

digestive tract and psychology of prey animals

Horse and DonkeysMouth- 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

Digestive tractNon-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

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)

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)

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

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 impactedThe cecum requires a very slow transition is

the diet is being changed

Colon Finishes fermentation Absorbs water

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

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

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

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

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. Fleshy2. Very thin 8. fat3. Thin 9. extremely fat4. Moderately thin5. Moderate6. Moderately fleshy

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

Forages Very important to provide pasture and hayGrass forages- Are low in Ca and high in PLegumes- 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

Forages ContinuedTall Fescue can be infected with endophytes- Not for use in pregnant maresAlfalfa- 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 colicTimothy hay is another good choice

Feeds for HorsesElectrolytes and Minerals- Especially important in endurance animals- Necessary for bursts of energy, utilizing

muscle glycogen- Needs vary by the animal and its useVitaminsBiotin- Improves hoof condition- Is very expensive to supplement in horses

Feeds for Horses ( cont)Carbohydrates- High grain diets can predispose them to

laminitisProtein- 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

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

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

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

Pre-cecal digestion and fat useProcessing 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

Oats Whole grain Good pre-cecal digestion in horses Additional processing is usually not an

advantage Crimping or micronized can decrease

pre-cecal digestibility

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

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

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

Feeding Programs for Horses Maintenance Reproduction Growth Performance Aging foals

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

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

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.

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

formation

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Starvation and Neglect Detrimental effects on the immune system,

digestive tract health, healing and body scoreFeeding a starved, neglected horse ( Stull, 2003)1. Days 1-3 one pound of leafy alfalfa every 4

hours2. Days 4-10 increase amount of alfalfa to four

pounds every 8 hours by day 63. 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

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

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

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

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 EWhite Muscle Disease- stiff, stilted gait, hopping in rear legs- Necropsy shows mottled white patches of

gritty feeling muscle

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

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