Ruminant Anatomy & Motility PDF

Rumen 1 - Anatomy & Motility https://www.boredpanda.com/cow-puns/ Anatomy Foregut fermentation 4 chambers Reticulum Rumen Dorsal Omasum...

Rumen 1 - Anatomy & Motility https://www.boredpanda.com/cow-puns/ Anatomy Foregut fermentation 4 chambers Reticulum Rumen Dorsal Omasum Cranial Abomasum Caudal Ventral https://www.toppr.com/ask/content/concept/digestion-in-ruminants-200952/  Anatomy Dorsal Cranial Caudal Ventral http://bvetmed1.blogspot.com/2013/03/ruminant-abdomen-lecture-157.html  Reticulum No sphincter separating the reticulum from the rumen Reticulorumen Allows small/dense digesta particles to move to the omasum Collects large particle/low density digesta for rumination http://vetstudentresearch.blogspot.com/2015/05/dig Traps heavy objects estive-physiology-and-anatomy-of-cows.html Hardware disease Contractions form esophageal groove in neonates Milk bypasses the rumen into the omasum  Rumen Microbial fermentation Large volume 100 -150 L in cattle Lined with papillae Surface area Absorption http://extension.msstate.edu/publications/publications/understand ing-the-ruminant-animal-digestive-system http://www.vivo.colostate.edu/hbooks/pathphys/digestion/herbivores/rumen_anat.html  Omasum Water absorption 30-60% of water entering Volatile fatty acid absorption 43-77% entering, 10% of total Prevents buffering of abomasum https://wellcomecollection.org/works/sk5ddgea Electrolyte absorption Mg2+, K+ Many leaves (lamina) “Butcher’s bible” https://www.stockfood.com/images/00286106-Cow-s-stomach-omasum  Abomasum Glandular “true” stomach Secretes HCl pH 2.5-3.5 Digestive enzymes Pepsin From pepsinogen Lysozyme http://extension.msstate.edu/publications/publications/understanding-the- ruminant-animal-digestive-system Digest bacteria Benefits of Ruminant Fermentation More extensive and efficient fermentation Able to break down fibrous plant material Rumination (chewing cud) = more mastication Microbial protein From plant protein and non-protein nitrogen B vitamins – can be absorbed in small intestine Cobalt for vitamin B12 Detoxification of plant compounds Disadvantages Takes a long time Slow transit of material through tract Rumen capacity limits feed intake Large volume Heavy and takes up space Only small particles (~2 mm) can pass to omasum Lower digestibility = slower passage rate Types of Ruminant 3 categories based on feeding behaviour Browsers Selectively eat high quality plant material Grain/seeds, fruit, leaves, bark, green stems Higher concentrate diet More frequent meals Faster fermentation = faster passage rate E.g. deer Types of Ruminant Grazers Indiscriminately eat most plant material Mostly grass Higher fiber diet Less frequent meals E.g. cattle and sheep https://www.dairyglobal.net/health-and-nutrition/health/grazing- behaviour-why-knowing-your-cows-counts/ Intermediate E.g. goats https://www.science.org/content/article/why-dirt-eating-goats-never-need-visit-dentist  Characteristic Browser Grazer Eating behaviour More frequent, smaller Less frequent, larger meals meals Rumination More frequent, shorter Less frequent, longer period period Oral anatomy Long jaw and tongue, thin Short, round tongue and or cleft lips jaw, thick muzzle Salivary glands Very large (high Smaller fermentation = more acid to buffer) Rumen anatomy Smaller rumen and Larger, especially omasum omasum, more muscular Intestinal anatomy Shorter SI, large cecum Longer SI, shorter cecum and colon (more hind-gut and colon fermentation) Transit time Faster (more rapid Slower (longer fermentation) fermentation needed)  Stratification Layers form based on particle density and size Low-density fiber raft Rumination Mastication ↓ size Fermentation Gas retention https://ebooks.publish.csiro.au/content/9781486309504/9781486309504/SEC8/F30 Rumen Motility Rhythmic contractions of the reticulorumen Functions Continuous mixing of contents Mixes with saliva → buffering Prevents pockets of high concentration Contact with epithelium →absorption Inoculation of feed particles with microbes Particle sorting (size) Rumination Chewing cud = more mechanical digestion Eructation Elimination of gas from fermentation  1°Contraction Cycle Major mixing cycle - loud Occurs ~1/minute Lasts ~20 seconds 1. Biphasic (double) contraction of reticulum 2. Contraction of cranial sac and cranial pillar 3. Contraction of dorsal sac Cranial to caudal 4. Contraction of ventral sac Cranial to caudal, then caudal to cranial 5. Relaxation of cranial pillar http://bvetmed1.blogspot.com/2013/03/ruminant- Digesta can move into reticulum abdomen-lecture-157.html https://norecopa.no/norina/rumen- motility-model 2°Contraction Cycle (Eructation) Occurs once for every two 1°cycles Release of gas produced from fermentation 30-50 L/hour in cattle Begins with same steps as 1° Contractions tilt gas pocket forward to cardia Opening of esophagus Allows gas to be released  2°Contraction Cycle (Eructation) 1. Biphasic contraction of reticulum 2. Contraction of cranial sac and cranial pillar 3. Contraction of dorsal sac 4. Contraction of ventral sac 5. Contraction of caudoventral blind sac 6. Contraction move cranially through caudodorsal blind sac 7. Contraction of ventral sac http://bvetmed1.blogspot.com/2013/03/ruminant- abdomen-lecture-157.html 2°Contraction Cycle (Eructation) Gas at cardia triggers relaxation of cardia and lower esophageal sphincter Will not relax if fluid/digesta is present Frothy bloat Inhalation causes negative pressure in esophagus Gas travels up into esophagus Some gas expired directly Majority (80%) is inspired into trachea/lungs first Expired on next breath Some gas can be absorbed into blood Rumination Regurgitation of digesta from reticulum “Chewing cud” Large particle size, low density Reticulum contraction just before 1° or 2° contraction cycle Triphasic https://stock.adobe.com/ca/images/head-of- Relaxation of esophageal sphincter ruminating-cow-collar-and-blue-sky/336718801 Bolus enters esophagus Reverse peristalsis of esophagus Moves bolus to mouth Tongue squeezes out liquid Mastication & salivation Rumination Cud (bolus) chewed for ~10-60 seconds Grazers > browsers Increased salivation = increased buffering Stimulated by long-stem fibers rubbing rumen epithelium More fiber = more rumination Effective fiber size Up to 10 hours per day Indicates a healthy, happy cow Control of Motility No autonomous smooth muscle contractions No cells of Cajal in the foregut Intrinsic nerve plexi (ENS) Does not produce motility contractions Small variations in smooth muscle tone May excite tension receptors Stimulates extrinsic motility Control of Motility Extrinsic control – autonomic nervous system Vagal nerve is required for rumen motility Cranial nerve X Parasympathetic nervous system Multiple branches Different regions of reticulum and rumen Coordination of movement Responsible for both 1° and 2° contractions Splanchnic nerve – sympathetic Inhibits motility Much smaller role than vagus nerve Controlled by the gastric centers of the medulla Affects frequency, duration, and amplitude of motility Activation is dependent on balance of excitatory and inhibitory signals from receptors Control of Gastric Centers Stimulatory signals Buccal mechanoreceptors Eating and chewing Rumen tension receptors Mild to moderate stretch Rumen epithelial mechanoreceptors – touch Rubbing of large fibers against rumen epithelium Abomasal chemoreceptors – acid Low pH = empty abomasum Control of Gastric Center Inhibitory signals High threshold tension receptors in reticulum and rumen Severe stretch, e.g. bloat Tension receptors in abomasum Reduce throughput of material into omasum Rumen epithelial chemoreceptors – acid Reduced motility = reduced fermentation = reduce acid Pain Especially abdominal/visceral pain Medications Sedatives, tranquilizers Rumen Tension Receptors Located in muscle wall Low to moderate distension Excites tension receptors Stimulates gastric centers Increased motility Severe distension Inhibits gastric centers = reduced motility Mechanism is not known Separate high-tension receptors? Gastric center responds differently to high rates of tension receptor firing? Rumen Epithelial Receptors Located in the epithelial lining of the rumen Mechanoreceptors Light touch Rubbing of long fibers against epithelium Stimulates salivation and rumination Chemoreceptors Low pH in rumen Inhibitory signals to gastric centers Decreases rumen motility Low pH in abomasum (i.e. when empty) Stimulatory signals to gastric centers Increased rumen motility RR = reticulorumen Fig. 27.11 from Duke’s Physiology, 12th Edition Evaluating Motility Visual Chewing cud Cud moving up esophagus Left paralumbar fossa Rippling Bloat Palpation Left paralumbar fossa https://www.sciencedirect.com/science/article/pii/S0022030219306 836 Should be soft Firm could mean bloat Evaluating Motility Listening (auscultation) Stethoscope in left paralumbar fossa Rumbling 1° contraction Should be ~1 per minute Splashing or tinkling Can indicate reduced motility Increased water in rumen from acidosis Percussion (tapping) Ping = displaced abomasum https://www.youtube.com/watch?v=dEyouroHsyA https://pressbooks.umn.edu/largeanimalanatomy/chapter/abdomen-2/ Decreased Motility Hypomotility = less than normal Atony or stasis = no motility Direct depression of gastric centers Medications e.g xylazine (Rompun, Anased) Acute phase proteins Fever Pain Hardware disease ↓stimulatory and/or ↑inhibitory signals Decreased Motility Failure of neuromuscular transmission Contraction requires signal from vagus nerve Increased sympathetic stimulation Splanchnic nerve