Ruminant GI

Gastroenterology Laboratory

• Location: Department of Biomedical Sciences, College of Veterinary Medicine, Tuskegee University, Tuskegee, AL 36088

Physiology of the Gastrointestinal Tract

• Instructor: Ayman I. Sayegh

Motility - Ruminant's Stomach

Anatomy

• Key Components of Ruminant Stomach:

  • Food Path: Rumen → Reticulum → Omasum → Abomasum → Small Intestines

  • Components:

  • Rumen

  • Reticulum

  • Omasum

  • Abomasum

  • Small Intestine (included in food path)

Anatomy Detailed

• Anatomy of the Ruminant's Stomach: Includes key structures like:

  • Rumen

  • Reticulum

  • Omasum

  • Abomasum

  • Small Intestine

  • Esophagus

• Structures Identified:

  • Cranial Pillar

  • Longitudinal Pillar

  • Cardiac Opening

  • Reticular Groove

  • Reticulo-omasal Opening

  • Ruminoreticular Fold

  • Various sections of Rumen (Dorsal Sac, Caudal and Ventral Sacs, Coronal Pillars)

Functions of the Stomach

• Rumen Functions:

  • Microbial Digestion

• Reticulum Functions:

  • Entrapment of Large Particles

• Omasum Functions:

  • Sieving Effect

• Abomasum Functions:

  • Enzymatic Digestion

Motility Patterns

• Pillars Function:

  • Stretch Receptors:

  • Detect distention, increase motility

  • Decrease motility if severe
    t - Chemoreceptors:

  • Detect changes in pH, decrease motility, increase absorption of volatile fatty acids (VFAs)

Food Path

• Order of Passage:

  • 1. Rumen

  • 2. Reticulum

  • 3. Omasum

  • 4. Abomasum

Rumination Process

• Separation of Ruminal Contents by Time:

  • Today's hay

  • Yesterday's hay

  • Role of gas in the rumination process

Motility Patterns in Ruminants

• Oral and Esophageal Motility:

  • Similar to other species

• Stomach Motility:

  • Two main cycles:

  • Rumen-Reticulum Cycle

  • Omasum-Abomasum Cycle

Rumen-Reticulum Cycle

• Primary Cycle (Mixing):

  • Separates ingesta by size (different zones)

• Secondary Cycle (Eructation):

  • Occurs at a rate of 1-3 per minute

  • Forces CO2 and CH4 to enter the esophagus

  • Liquids move down, solid particles separated by gravity and contraction

Contraction Details in Rumen-Reticulum Cycle

• Primary Contractions:

  • Reticular Contraction

  • Caudal Contraction of Dorsal Sac and Ventral Sac

  • Secondary Contractions:

  • Cranial Contraction of Dorsal Sac and Ventral Sac

Ruminal Zones

• Zones classified by particle size and specific gravity:

  • Zone of Potential Escape: Small particles

  • Slurry Zone: Larger particles

  • Ejection Zone

  • Liquid Zone

Secondary Cycle - Eructation

• Mechanism:

  • Cranial contraction of the dorsal sac

  • Ventral relaxation of the ventral sac

  • Dorsal elevation of the cranial pillar

  • Cardia relaxes

  • Involves inspiratory excursion (lung expansion) with a closed glottis

  • Retro-peristalsis moves slurry zone to esophagus

Regurgitation Process

• Mechanism involves:

  • Tongue expressing contents

  • Water is swallowed

  • Size-based isolation of particles:

  • Large - Slurry Zone (for reprocessing)

  • Small – Zone of Potential Escape

  • Commencement of remastication

• Effect of diet:

  • High Grain Diet → Minimum rumination

  • High Forage → Maximum rumination

End of Rumeno-Reticular Cycle

• Contraction of cranial sac moves the zone of potential escape from the rumen to the reticulum

Rumination Timing

• Minutes per hour spent ruminating: Sample calculation indicates time spent:

  • 60 minutes total in an hour with differentiated time: Ruminating vs. Grazing (6 AM to 6 PM example)

Rumination During Rest

• Not sleeping, serves to separate contents:

  • Small particles vs. Large particles

Impact of Food

• Motility Changes:

  • Solid food increases motility more than liquids

  • Increases the rate of rumination

Disorders Related to Motility Failures

• Consequences of failed rumination:

  • Accumulation of gas

  • Accumulation of volatile fatty acids (VFAs)

Reticular Contraction Motility

• Mechanics include:

  • Omasal orifice dilation (sieving effect)

  • Canal contractions force food into the leaves

  • Absorption of VFAs and bicarbonates into the omasum

  • Omasum contractions push food into the abomasum

Reticular Groove and Milk Flow

• Relationship with pathways in ruminant anatomy:

  • Between Mouth and Abomasum:

  • Muscular fold acts as a trough for the passage of milk from rumen to abomasum in unweaned animals (contracted) versus weaned (relaxed) animals.

Reticular Groove Closure

• Influenced by various factors:

  • ADH (Antidiuretic Hormone)

  • Dehydration

  • Chemicals (e.g., copper sulfate for medication)

Omasal Digestion Variability

• Dietary changes impacting infants vs. adults:

  • 10% nutrient loss in the rumen

  • Milk typically bypasses the rumen, directly entering abomasum

  • Role of vagal stimulation in the process

Abomasum Functions

• Enzymatic Digestion:

  • Sensitive to changes in pH

• Functions as a reservoir / antral pump / gastric emptying mechanism

Clinical Considerations in Motility

Motility-Related Clinical Cases Explained

• Clinical disorders include:

  • Bloat: Excessive gas formation leading to distention of the rumen

  • Traumatic Reticulo-Pericarditis (TRP): Known as "hardware disease" stemming from foreign bodies penetrating the reticulum

  • Increased Slurry Zone: Impacts transport failure through the omasum

  • Vagal Indigestion: Affects overall motility and digestive function

  • Left Displacement of the Abomasum (LDA): Abomasum's abnormal positioning

  • Right Displacement of the Abomasum (RDA): Similar to LDA but in the opposite direction

  • Hypomotility: Reduction in general motility leads to gas accumulation and digestive issues

Clinical Signs for Bloat

• Physical sign of discomfort or distress in ruminants when bloating occurs.

Treatment Options for Bloat

• Multiple treatment methods exist, depending on severity and specific case conditions.

Traumatic Reticulo-Pericarditis (TRP) Characteristics

• Symptoms:

  • Arched back posture indicating pain

  • Edema in respiratory or abdominal regions

  • Abducted elbows indicating discomfort and restriction of movement

Surgical Options

• Rumenotomy: Surgical opening of the rumen often for treatment of bloating/other disorders

Displacement Positions of the Abomasum

• LDA: Left Displacement of the Abomasum (visually maintain positions of surrounding organs)

  • Normal anatomy recognition of displacement in diagrams

• RDA: Right Displacement of the Abomasum (similar recognition of organ positions in diagrams)