Equine G.I tract

key principles in horse digestion

• Hindgut-fermentative digestion

• Non-rumiannt herbivore

• Hindgut fermenter

• Foregut enzymatic digestion

Ruminant vs non-ruminant

Rumiannt: uses rumen for fermientation, usually less picky

non-ruminant: After small intenstine fermentation (horse uses cecum), moresentitive

Note about enzymatic digestion in horses

dosnt really begin until the small intestine

Laminitess

High grain diet leads to too much sugar and startch

Also common in dairy cattle

Importance of pelvic flexure

Big diameter to small diameter

Leads to bottle neck

connects the left ventral colon to the left dorsal colon

Development of Gi tract

• tract is small in neonatal foal

• tract increases in size while liver remains the same

• Small intestine increases until 4 weeks

• Large intestine keeps growing

Mouth characterisitics for horse

Mechanical breakdown of food, saliva production, and initial digestion occurs.

Prehensile lips

Ingestine - slower than rumiannts, they graze longer

Mastication (chewing) higher for roughages vs concentrates

Why is the TMJ important

Joint that opens the mouth

What kind of teeth do horses have

hyposodont - continuesly growing teeth

Teeth in horses

condition of teeth affects feed efficiency

they chew in a circular motion

Salivarary glands

Helps lubricate

Less enzymatic digestion b/c no salivary amalase

why is saliva important

bicarbonate → helps neutralize and helps with grain digestion

lubricates

Parotid, sublingual and mandibular glands

• 10 gallons saliva / day

• no enzymatic digestion

• buffering capacity & lubrication

  • buffers unprotected upper stomach

  • allows bacteria in stomach to survive

  • Bicarbonate; NaCl; other electrolytes

Cardiac sphinctor

prevents regurgitation in horses

Between the esophagus and stomach

Esophagus

Transports food from mouth to stomach

4-5 feet long

Peristalisis

VERY muscular

Left side of trachea

Problems with esophagus

They can choke

• eat to fast

• dont chew food well

• no salivia

• nasal discharge

Group fed isnt good for pelleted feed unless you soak them to prevent chokcing

Equine Stomach

Very acidic environment

10% of GI capacity

ROP is fast: No abosprtion

Should not be empty

• increase gas production → rupture

4 important parts of the stomach

Sphincters: cardiac + pyloric

Mucosal surfaces

Fundic region

Pyloric region

Mucosal surfaces

Squamous epithelial - non glandular - ½ of stomach

glandular epitheal - mucosal

• fundic & pyloric

Fundic region

Parietal cells -HCL: helps prepare carboyhydrates + proteins to be broken down

Cheif cells - Pepsin: enzyme that digests protein

• HCl activates zyomogen cells to secrete pepsin

Where does bile come from horses

Liver → they dont have a gallbladder

Pyloric region

Gastrin

Mucus

Extremely acidic

margo plicatus

a distinct dividing band inside a horse's stomach that separates the upper non-glandular region from the lower glandular region

• separates squamous from glandular epithelium

Where is the primary site of non-glanudlar ulcers?

near the esophagus

Where is the primary site of ulcers in stomach

*NEED TO DOUBLE CHECK

Near the pyloric gland region (pylorous spynctor)

Very acidic (PH of 2.5)

Fermentative digestion in stomach

**write after office hours

Enzymatic Digestion in stomach

**write after office hours

Fundus/Body region characterists

• PH decreases to 5.4 in distal end

• Decreased fermentation

• First site of enzymatic digestion of protein

Pyloric region characteristics

• PH decreases to 2.6

• Stops fermentation

• Secretion of HCl increases

Ulcers

Esophageal area where ulcers occur → around margo plicatus

Gastric secretions constant even if stomach is empty → leads to ulcers

Equine Gastric Ulcer Syndrome (EGUS) causes

Bile secretions continual —> fasting increases chances

High grain; less hay/grass

Stress/excerise: Sloshing of stomach acid, cortisol decreases prostagladin (protects against ulcers)

Medications such as NSAIDs

Constant secretions

How common are ulcers

90% of racehorses

60% of performance horses

25-50% shown in foals

EGUS symptoms

Attitude changes: nervous or more tired

Changes in performance

Lots of laying down

Colic

Poor appetitie

Teeth grinding

Poor hair coat

Diffrent ulcer grades

Grade 0: No evidence

Grade 1 Inflammating: areas of reddening and hyperkeratonis

Grade 2 Erosion: small single or multiple ulcers

Grade 3 Progressive ulceration: Large single or extensive superficial lesions

Grade 4 Full ulceration

Most difinitive diagnosistic tool for ulcers

Gastroscopy with endoscope

Gastroscopy metholodgy

Gastroscopy preparation

• Fasted - empty stomach. This alone can lead to ulcers

Measures severity and location

Examples of prescription medications for ulcers

Omeprazole

Sucralfate - bind to stomach ulcers

antacids - neutralize stomach PH

Other treatment alternatives for ulcers

• acupuncture

• herbals

• food therapy

• supplements

• dietary management

• decreasing grain

Ulcer prevention

Management

• decrease grain, decreases gastrin which decreases HCL=l

• increasing grazing time or hay, keeps gut full and increases salivia production

Oil supplmentation

Decrease workload

Known stressful situation - omeprazole (FDA, Gastrogard 28 day treatment)

Small intestine

30% of the tract

primary site of digestion and absorption

Fast ROP

No bacteria to detoxify

Small Intestine anatomy

Duodenum - Proximal

• Disaccharidases

• Bile duct

• Pancreative duct for enzymes

Jejunum

Illeum - Distal

Important components/jobs of small intestines

Lactate prodicted in stomach is absorbed and coverted to VFA in LI

Amylase in SI increases with startchy feeds

Enterocytes have microvilli which increase surface area and absortpion

4 important Pancreatic Enzymes

Carbohydrases: 50-70% dig/absopred from pancreatic activity

Lipase: break down fat

Proteases: break down protein, 100%, Trypsin, chymotryripsin

Bicarbonate: Buffers the low pH from the stomach

Bile

Continuously funneled into duodenum from liver

• fluxes into distal stomach for fat emulisification

Duodenum importance

Fat emulisification

Liver

Function → metabolism

• glycogen storage

• hormone production

• protein metabolism

Bile production

portal vien

breaks down hemoglobin

Cecum

Large in the horse

Significant fermentation

VFA production

Microbes specific to feedstuff

ROP slow

Microbes in Cecum

specific to feedstuff: takes 3 weeks to change gut microbe population

Microbes produce vitamin k, B complex, protein and VFA

Large intestine

very large capacity

slow passage

colic possible at flexures… such as pelvic flexure

abosorption of fermentation products

Protozoa

Larger than bacteria

role in fiber digestion

defaunation not harmful - digestion wont suffer

bacteria

populations include amylotltic (lower PH, increase in grain leads to increase), cellulolytic (neutral pH) and proteolytic

Highest in cecum and ventral colon

Hindgut ulcers

right dorsal colon

44-63% of horses

Stress, hindgut acifosis, NSAIDS, parasites

Weight loss, diarrhea and colic are most common

Decreased performance and rough haircoat

Probiotics

Adding live microorganisms to the gastrointestinal tract of horses to improve microbial balance and digestive health.

Needed in time of stress

in feed products probiotics die as part as feed processing due to high heat

antibiotics strip gut of microbes

Common types of problems with teeth

• Sharp enamal

• Hooks

Where is the primary site of ulcers *true correct one

near the cardiac spynthictor

Where the esophagous ocnnects

Fermentatative Diestion in stoamch

very small amount

Starch and sugar are converted to lactic acid

Bicarbonate reversible formula

CO₂ + H₂O ←→ H₂CO₃

3 types of lipases

1. pancreatic lipase

2. hormone sensititve lipase

3. lipoprotein

What happens in the Duodenum

Fat emulsification

Fat is broken down from big glob into smaller globs

• Micelles turn into chylomicrons which go into bloodstream

Sacculated and teniae

Terms to describe cecum and large intestine

sacculated: helps it stretch

tenaie: ribbon that aids in mobility

Amylolytic vs cellulolytic vs proteolytic

Amylotic more acidic conditions, thrives when there is alot of startch to break down

Cellulotic is the main one, more neutral PH, thrives with cellulose + fiber

Proteolytic enzymes function in all conditions, primarily breaking down proteins into amino acids.

What could cause acidicosis in horse

• high grain diet

Diet affects if high in hay

Higher PH

High acetate

low proprionate

Diet affects if high in hay and concentrate

lowerish PH (still neutral)

very high acetate

slight increase in propionate

Diet affects if fasted

higher PH
lower acetate
higher propionate

Hindgut acidosis

Consuming a diet high in startch concentrates (grain)

Drop in pH below 6

Startch fermantation begins

• we dont want this

Importantce of feed processing

Cracks seed holes open to allow carbohydrates through

• cracking

• steamed

• hopped

Must be processed for effective digestiability

Pre-cecal startch digestion

we want this

Oat > barley > corn

• corn needs to be processed

Mechanical, therman and hydrogethermal processing

• increases prececal but not total tract digestability

• benefitical in high grain diets

• reduced hingut fermentation which can lead to health risks such as gas production, acidosis, leaky gut, ulcers and colic

Enzymatic vs fermentation products

Carbs → glyucose

Fiber/ structure carbohydrates → VFA