VBMS 324 MOD 5 rumen motility

need for rumen motility: 1st contraction

• inoculate ingesta with bacteria and protozoa

• prevent local accumulation of VFA at site of production

• mixes saliva and ingesta to buffer acids produced by bacteria

• assist VFA absorption through rumen wall

• prevent impaction by moving small particles into lower GI

need for rumen motility: 2nd contraction

elimination of gas produced by bacteria

rumination

allows re-chewing the food to reduce forage particle size and and saliva, which supports efficient microbial fermentation

ENS role in motility

• generates basic local contractions

• cannot coordinate full motor patterns

• vagotomy= contractions persist but uncoordinated

vagus nerve role

• provides central pattern generator

• afferents = CNS gastric centers = efferent motor output

• controls exact reticulorumen sequence

Intrinsic motility

• ENS

• low amplitude variations in smooth muscle tone

• does not produce propulsive contractions

• may excite sensory tension receptors that can induce extrinsic motility

extrinsic motility

• vagal nerve; cranial nerve X, parasympathetic, multiple branches innerve reticulum and rumen

• does both 1st and 2nd contractions

• fires based on activity in the bilateral gastric centers of the medulla

inhibition of extrinsic control

• other innveration of forestomach

• splanchic motor nerves (sympathetic)

• inhibit motility

gastric center regulation: stimulatory

• buccal mechanoreceptors (eating and chewing)

• tension receptors (to vagal and splanchnic nerves)

• epithelial receptors (to vagal)

gastric center regulation; inhibitory

• tension receptors reticulum detect extreme distention

• tension receptors in abomasum and rumen

• pain

• drugs

Tension receptors

• monitors tension in muscle wall

• low/moderate distension excite tension and increase motility

• high tension causes inhibition of motility

epithelial receptors

• mechanical stimulation: light touch causes rumination and severe distention inhibits motility

• chemical stimulation: acid in rumen will inhibit signals to gastric center (decrease motility) and acid in abomasum cause stimulatory signals (increase rumen motility)

primary cycle

• about 20 sec long

• double contraction of reticulum

• contraction of dorsal rumen sac (cranial to caudal)

• contraction of ventral rumen sac

• LOUD

primary cycle contraction sequence

1. reticulum x2 (cranial to caudal)

2. dorsal sac (cranial to caudal)

3. ventral sac (caudal to cranial)

secondary cycle

• occurs after alternate 1st cycles

• eructation

secondary cycle contraction sequence

1. caudoventral ruminal blind sac

2. dorsal sac (caudal to cranial)

3. ventral sac (caudal to cranial)

pressure during eructation

animal inhales, creating neg pressure in thorax drawing gas into the esophagus

eructation

• microbes produce lots of gas

• gas build-up occurs in dorsal rumen

• 2nd contraction moves gas to cardia region of the reticulum

• gas causes reflex opening of cardia and caudal esophagus

what prevents eructation?

fluid/froth covering cardia

measuring rumen motility

• 3 catheters placed in fistula (one in reticulum, one in dorsal sac, one in ventral sac)

• catheters connect to polygraph to measure as contraction passes the location of catheter tip

rumination

• regurgitating

• chewing cud

• high frequency in roughage diets

• indicator of good health

rumination sequence

1. before 1st contraction, reticulum contracts

2. neg pressure created by inhalation while airway closed

3. cardia and distal esophageal sphincter relaxes

4. cud goes in esophagus and move up with esophageal reverse peristalsis

5. tongue squeezes fluid out

6. cud chewed for 10-60 sec

7. cud shallowed

extra chewing causes..

• buccal receptor stimulation

• smaller particle size

exam of rumen motility

• examine rate and strength of contractions

• look for bloat

• auscultation (stethoscope on left paralumbar fossa)

• external palpation

• rectal exam

decrease ruminoreticular motility

• hypomotility: reduced motility

• atony or stasis: no motility

• can be primary or secondary sign

• caused by drugs, acute phase proteins, pain

conditions causing reduced motility

1. animal not eating (lumpy jaw, wooden tongue)

2. displaced abomasum

3. traumatic reticuloperitonitis (hardware disease)

4. bloat

5. rumen impaction

6. rumen acidosis

7. hypocalcemia (milk fever)

8. vagal indigestion

9. stress/fear

10. drugs

frothy bloat

• more common than gas bloat

• ingestion of some legumes/alfalfa causes froth in ruminoreticulum

• gas bubbles produced by bacteria

• froth covers cardia and inhibits eructation reflex

• high rumen pressure

displaced abomasum

• right or left displacement

• LDA more common

• abomasum distended with air or fluid

• stimulation of abomasal tension receptors

• increase inhibitory tension receptors

• pain

traumatic reticuloperitonitis

• hardware disease

• foreign object pokes through reticulum or rumen

• direct depression of gastric center

• inappetance

free gas bloat

• failure to eructate

• high rumen pressure

rumen impaction

• ingestion of large quantities of poor quality or indigestible feed high rumen pressure

• leads to rumen distention

ruminal acidosis

• carb engorgement or “grain overload”

• ingestion of large quantities of grain

• highly fermentable and changes rumen bacteria population

• more lactic acid production

hypocalcemia

• milk fever

• common periparturient disease of dairy cows

• low plasma calcium

• failure of neuromusclear transmission

vagal indigestion

• vagal nerve responsibility for ruminoreticulum motility

• vagotomy stops motility, rumination and eructation

• lack of motility= vagal nerve dysfunction