MHU/HQ September 2012: Digestive Anatomy

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 WilliamsRutgers University

Meet our presenter:

Dr. Carey WilliamsRutgers University

Danielle Smarsh, Doctoral CandidateRutgers University

Question facilitator:

FOREGUT:• Mouth• Stomach• Esophagus• Small Intestine

HINDGUT:• Cecum• Large Colon• Small Colon• Rectum

Mouth

• Function:– Selection– Chewing– Saliva– Swallowing

• Teeth:– Incisors: shear forage– Molars: grind food

(Hill, 1997. Horse Health Care)

Teeth Floating

Choke

Endoscopy of an esophageal

obstruction

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!

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

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!

Large Intestine

• Large Intestine: • Cecum• Large and Small colon• Rectum

– Forage fermentation– Water absorption

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

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

Microbial Digestion

Microbes

Fiber from forage & other undigested residuals

VFA’s, B-vitamins, Vitamin K, Gas

Avoid Abrupt Changes

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

Large Colon

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

NutrientsSite of: Digestion Absorption

Water ------- Colon

Protein Stomach & SI SI

Lipid SI SI

CHO's

Simple SI SI

Complex

Starch SI SI

Structural LI LI

MonogastricsMouth

Stomach

SI

Cecum

Colon

Prot absorption, lipid dig/absorp,Simple CHO dig/absorp

Complex CHO fermentation

Complex CHO fermentationAbsorption of water

Protein digestion

Grains and Forages for Horses

Roughages vs. ConcentratesRoughage Concentrate

Fiber High Low

Energy Low High

Protein Variable Variable

Cost Lower Variable

Density Low (bulky) High

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

Pasture

• Grasses:• Cool season: – bluegrass– orchardgrass– timothy– tall fescue

• Warm season:– bermuda– bluestem– sudan

OrchardgrassTimothy

Pasture

Legumes:• Alfalfa • Clover

Hay

• Hay:• Grasses and legumes are

cut to make hay• Orchardgrass/Alfalfa• Legumes have higher:

• protein• energy• TDN• COST!

Hay Quality• Never feed dusty or moldy hay!• Quality depends on:– Plant Maturity• No seed heads

– Leafiness• Smaller stem size

– Smell– Color– Weeds/Debris

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

Concentrates• Grains:• Fiber - low (2 -10%)• Energy - high• Protein - low (8 to 10%)• Cost - reasonable– Examples

• Corn• Oats• Barley• Sorghum

- most popular - lower energy value - higher fiber - more palatable and digestible- can be expensive

- palatable - 2 x energy as oats - low in fiber- easy to over feed- moldy is lethal

- small hard kernel - not palatable- used in grain mixes - high energy - low fiber

- mostly for humans- expensive- small hard kernels - high energy- low palatability

- hard hulls- medium fiber & energy

OATS CORN

WHEAT MILO BARLEY

- byproduct of grain processing is oil- 35 % protein- 85 % is digestible

FLAXSEED

- high-energy ingredient- usually as part of a mixture- kernel has high nutritional value- the plant itself is a good roughage source

RYE

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

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

Feeding Guidelines

• Feed by weight not volume! – 1 lb oats is not 1 lb of corn

• Monitor condition scores – Score of 5 is appropriate

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

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

Carey Williams, Ph.D.

Equine Extension Specialist

[email protected]

www.esc.rutgers.edu

Thank You!

Better horse care through research & education

Equine Science Center

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Upcoming Webcasts

• Protein Requirements for HorsesOctober 23, 2012 | 7PM EDT

• Equine EnergeticsNovember 27, 2012 | 7PM EDT

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