1. Rumen Motility Church: 67-106, 108-116, 468-474 Van Soest: 237-244 Ruckebusch and Thivend: 35-51; 103-119 Sjersen et al.: 155-164 Susenbeth et al. 1998. Energy Requirement for Eating in Cattle. J. Anim. Sci. 76:2701-2705. http://jas.fass.org/cgi/reprint/76/10/2701.pdfhttp://jas.fass.org/cgi/reprint/76/10/2701.pdf Mawuenyegah et al. 1997. Effect of Ammonia Treatment or Protein Supplementation on Rumination Behavior in Sheep Given Barley Straw. Animal Science 64(3):441-445. http://www.bsas.org.uk/Publications/Animal_Science_PDF_Back_Issues/ Animal_Science_PDF_Back_Issues/ Cheng et al. 1998. A Review of Bloat in Feedlot Cattle. J. Anim. Sci. 76:299-308. http://jas.fass.org/cgi/reprint/76/1/299.pdfhttp://jas.fass.org/cgi/reprint/76/1/299.pdf Majak et al. 1995. Pasture Management Strategies for Reducing the Risk of Legume Bloat in Cattle. J. Anim. Sci. 73:1493-1498. http://jas.fass.org/cgi/reprint/73/5/1493.pdf

2. Rumen contractions Functions –Inoculate incoming feed –Mix contents Minimize effects of stratification Move fermentation products to rumen wall –Particle sorting –Particle passage –Rumination –Eructation of fermentation gases Location –Contractions are contractions of an entire sac of the reticulorumen, but are the result of muscular contraction primarily on the pillars

3. Types of reticular contractions Biphasic contraction –Action Reticulum contracts to about ½ its size, relaxes, and contracts completely Reticulo-omasal orifice is open during contraction, but closes when reticulum dilates –Assists in digesta passage from the reticulorumen –Passage more closely related to duration (r 2 =.76) than amplitude (r 2 =.56) or frequency (r 2 =.15) –Duration 7 to 12 seconds –Frequency Eating – 35 to 45 seconds Resting – 75 seconds Triphasic contraction –Action An extra complete contraction precedes a biphasic contraction of the reticulum Contraction is associated with the movement of digesta up to the cardiac sphincter before rumination.

4. Types of ruminal contractions Primary contraction –Also called A-wave or backward moving –Action A biphasic contraction of the reticulum Anterior pillar contracts lifting the anterior sac. –Anterior fold rises to form barrier Contraction moves across dorsal sac to dorsal blind sac from contraction of longitudinal pillar and dorsal coronary pillar Dorsal blind sac contracts and dorsal sac relaxes from dorsal coronary pillar Ventral sac contracts along longitudinal pillar Ventral sac relaxed and Ventral blind sac contracts –Ventral contraction absent during rumination –Functions of the primary contraction Mixing and inoculation of digesta Particle sorting across the reticuloruminal and anterior folds –Duration of contraction Fed animal – 30 to 50 seconds Fasted animal – 12 to 18 seconds

5. The primary contraction of the rumen

6. Secondary contraction –Also called the B-wave or forward-moving contraction –Usually occurs after a primary contraction –Action Contraction of the ventral blind sac continuing up through the dorsal blind sac using the dorsal coronary pillar Contraction proceeds across dorsal sac forcing gas pocket to the cardiac sphincter –Function Eructation –Duration 30 seconds

7. Incidence of pressure waves Contraction Activity D DV DSV DVSV Feeding 1 27 5 56 Resting 10 35 25 22 Ruminating 22 28 37 6 Reticulum Cranial sac

8. Neural control of reticuloruminal contractions Nerves –Vagus nerve involved both in stimuli and inhibition –Sphlanchic nerve involved in inhibition Stimuli for contractions –Stretch Most common Receptors –Low threshold receptors »Tension receptors »Stimulated by pressures greater than 4 mm Hg »Stimulate contractions –High threshold receptors »Epithelial receptors »Stimulated by pressures greater than 20 mm Hg »Inhibit contractions –Tactile stimulation Near cardiac sphincter Epithelial receptors –Stimulates triphasic contraction of reticulum –Low abomasal pH Stimulates ruminal contractions –Hypoglycemia

9. Inhibition of ruminal contractions –Abomasal distension –Hyperglycemia

10. Factors affecting ruminal contractions Feeding –Increases frequency and amplitude of contractions Activity Contractions/min Amplitude P/S mm Hg Resting 1.2 18.2 - Feeding 2.0 22.1 1:1 Ruminating 1.1 10.4 - Fasting.3 Weak 5:1 Diet –Feeding a finely ground forage Reduced rate of contractions Reduced amplitude of contractions –Requires 2-6 weeks to adapt Volatile fatty acids –Acetic, propionic, and butyric acids at 90, 50, and 37 mM given separately or at 33.5, 29.3, and 21.1 mM given as a mixture will inhibit primary contraction Metabolic problems –Hardware disease, hypocalcemia, or hyperglycemia will inhibit ruminal contractions

11. Need for eructation Gas production –Peak Occurs 30 min to 2 hr post-feeding 12-27 l/min –Average 1-2 l/min Approximately ¼ to 1/3 of CO 2 produced in rumen is absorbed into blood and removed through the lungs Only 1/5 of the CH 4 is removed through the lungs Composition of rumen gas __Gas__ _%__ CO 2 65.35 CH 4 (variable) 27.76 N 2 7.00 O 2 (at wall).56 H 2.18 H 2 S.01

14. Mechanism of eructation Biphasic contraction of reticulum Modified primary contraction of rumen Secondary contraction of rumen Ruminal gas pocket forced forward Anterior fold and reticuloruminal fold rise to hold digesta away from cardiac sphincter Cardiac sphincter relaxes allowing esophagus to fill with gas Rapid reverse peristallsis of the esophagus –Diaphragmatic and Pharyngeal sphincters open –Nasopharyngeal sphincter closes Epiglottis opens while thoracic muscles contract –Cause 80% of gas to enter trachea –Acts as a muffler Animal exhales

15. Control of eructation Stimulus –Gaseous distension of the reticulum and rumen Inhibition –Presence of digesta near the cardiac sphincter Affects all three sphincters Prevents digesta from entering lungs –Epinephrine –Histamine Inhibition of eructation will cause the animals to bloat –Ruminal pressures will increase to 45 to 100 mm Hg.

16. Bloat Types of bloat –Free gas bloat Gas pocket over the digesta is normal, but can’t be eructated because of a physical obstruction in the esophagus or anatomical abnormality –Frothy bloat Gases form a foam over the digesta that inhibits eructation when it touches the reticular wall near the cardiac spincter Two types –Feedlot bloat –Pasture or legume bloat

17. Feedlot bloat Etiology –Occurs in ruminant animals fed high grain diets particularly during adaptation to the diets Causes –Digesta becomes viscous and gel-like that trap gas as a foam Viscosity increased by –The presence of bacterial capsules on some gram + starch-digesting bacteria such as Streptococcus bovis and lactobacilli »Streptococcus bovis and lactobacilli only found in large numbers in animals not adapted to high grain diets –The presence of short-chain starches (dextrans) –Increased concentrations of VFAs Reduce ruminal motility –Increased intake of a dense diet Lowers cardiac sphincter –Increased numbers of mucinolytic bacteria Mucin will prevent foam –Reduced outflow rate

18. Prevention –Slowly adapt animals to high grain diets –Feed adequate fiber –Use less fermentable grains Wheat or barley > Corn or sorghum Steam-flaked > Coarse ground –Feed ionophores (Monensin or Salinomycin) Decreased growth of Streptococcus bovis and lactobacilli Decreased feed intake Decreased methane production

19. Pasture bloat Occurs in ruminant animal consuming fresh legumes such as alfalfa, white clover and red clover or the small grain wheat when immature or immediately after a frost Causes –Presence of high concentrations of soluble protein present in chloroplasts increases surface tension causing foam Earlier research implied that a protein named ribulose-1,5- biphosphate carboxylase oxygenase (also called the 18S protein) –3 – 6% of DM in bloat-causing legumes Recent research shows that total soluble protein concentration is more highly related to bloat –Rapid cell wall digestion Rapid release of chloroplasts Rapid release of cell wall fragments that get trapped in foam –Pectin A cell wall component in high concentration in legume cell walls Pectin metabolism –Pectin fermented to Pectic acid (binds 2000x its weight in water increasing viscosity) –Pectic acid rapidly fermented to methane

20. –Minerals K, Ca, Ni, Zn, and Mg stabilize foam Frosted legumes –K is released into cytoplasm –Decreased Na:K ratio results in increased binding between proteins –Increases surface tension causing bloat –Decreased chewing Decreased salivary mucin and Na Mucin prevents foaming –Reduced ruminal outflow Retention time of CoEDTA, hr Nonsusceptible 8 Susceptible 12-17 Increases concentrations of chloroplasts and chlorophyll –Saponin Surfactant glucoside Minor role in stabilizing foam –pH less than 6 Stabilizes foam –Toxic factors Amines like histamine reduce motility

21. Legume bloat prevention Mix grasses with legumes in pastures Allow legumes to mature before grazing Use of non-bloating legume species –Birdsfoot trefoil, sanfoin, crownvetch, berseem clover, and some cultivars of red clover –Produce high concentrations of tannins Polymers of phenolic compounds Actions –Binds proteins preventing release –Reduce rate of digestion Feed some dry hay before putting animals on pastures Move to new paddocks after early morning –Not related to dew –Appears related to selective retention of chloroplasts Increase grazing pressure –Forces animals to increase consumption of stems to leaves Close availability of water

22. Use of surfactants –Vegetable oil –Poloxalene (Bloatguard) Effective at 10 gm/1000 lb/day May be used as drench, block or loose supplement Questionable palatability Antibiotics –Penicillin and tylosin Prevents bloat for a short period Bacteria adapt causing bloat –Ionophores Decreased incidence by 50%, but didn’t prevent it Genetic selection –After 10 years, bloat removed from herd –Phenotype difference Increased rumen liquid volume

23. Rumination Functions –Rechewing to increase particle size –Saliva flow Particle breakdown –Chewing during eating Functions –Preparation for swallowing –Release soluble constituents –Damage plant tissues for microbial attachment –Chewing during rumination Functions –Decrease particle size for passage –Damage plant tissues for microbial attachment –Microbial digestion –Reticuloruminal contractions

24. Particle size reduction Alfalfa Meadow Ryegrass Red clover Alfalfa hay hay ( % of intake) DM digested in RR 59.9 61.7 55.3 37.1 49.3 Soluble DM released 36.8 37.6 31.9 22.9 20.4 by chewing during eating Large particles reduced to < 1 mm by: Eating 11.8 14.0 14.5 14.3 14.4 Ruminating 12.0 13.7 16.4 26.6 38.5 (% of particle reduction) Particle reduction by 50.4 49.4 53.1 65.0 72.8 rumination

25. Mechanism of rumination Triphasic contraction of the reticulum –Forces digesta to cardia Animal inhales with epiglottis closed –Produces a vacuum of 60 to 80 mm water in esophagus Cardia opens and esophagus dilates –Negative pressure sucks digesta into esophagus Rapid reverse peristalsis moves digesta to mouth Bolus is rechewed –Chewing is slower and more deliberate than during eating Digesta reinsalivated –Saliva composition is different than during eating Parotid glands secrete more saliva during rumination than eating –Saliva from parotid glands secrete more HCO 3 - than other glands Reswallowing –After reswallowing, the rumen undergoes a primary contraction to move it back in the rumen –20 to 65% of the DM is released in a fine state and will not return to the mouth again

26. Control of rumination Controlled by tactile receptors (epithelial receptors) near the cardiac sphincter, reticuloruminal fold and anterior sac Stimulated by scratching of feed against the rumen wall Reflex is semiautomatic –Can be stopped anytime EEG resembles sleeping

27. Rumination time Average times for a grazing animal –Eating – 8 hours –Ruminating – 8 hours –Resting – 8 hours Ruminating time is quite variable Factors affecting rumination time –Fiber content of diet –Physical form of diet

28. Effects of diet on rumination Increasing the proportion of grain in the diet will decrease rumination Chews/day Hay 50,100 Dried grass 36,100 Concentrate 11,000 Increasing the maturity of the forage in a diet will increase rumination Decreasing the particle size of the diet will decrease the rumination time Increasing feed intake will reduce the rumination time per gm of feed consumed Cattle ruminate less per kg NDF than sheep or goats

29. Roughage value index Total chewing, min/kg DM Alfalfa hay, Chopped 44.3 Long 61.5 Pelleted 36.9 Oat straw 160 Cottonseed hulls 30.1 Alfalfa silage Fine chop 22.3 Medium chop 26.0 Corn-ground 5.1 Soybean meal 6.0 Minerals 0 Molasses 0 Urea 0

30. Effects of rumination of the animal Saliva flow –More saliva secreted during rumination than eating –Affects Rumen pH –Fiber digestion –Microbial growth –VFA and methane production –Maintenance of intake –Structure of rumen epithelium –Prevention of liver abscess and laminitis Liquid rate of passage –Efficiency of microbial growth within the rumen DM intake –Ruminating time is a limiting factor controlling intake of high fiber diets Maximum time, hours Ruminating 10-11 Grazing 13 –Lower rumination efficiency (min/g CWC) limits intake of smaller and growing animals

31. Body weight Rumination Max. CWC intake/d Animal kg kg.75 min/g CWC g/kg BW g/kg.75 BW Lambs 40 16.0 2.05 5.8 14.6 Goats 39 15.6 1.30 9.4 23.7 Mature sheep 82 27.3 1.18 4.9 14.9 Calves 119 35.9.78 5.2 17.2 Heifers 1 213 55.7.42 5.4 20.8 Heifers 2 342 79.6.19 7.4 31.8 Heifers 3 456 98.6.16 6.5 29.9 Mature cows 561 115.0.10 8.2 40.1

32. Energy cost –Total chewing increases maintenance cost by.24 kcal/hr/kg BW and accounts for 30% of maintenance requirement Accounts for difference in maintenance energy requirements of cattle fed high grain or high forage diets. –Contribution of rumination to energy cost of total chewing varies Time, min/kg DM consumed Feedstuff Eating Ruminating Oat straw 41-58 94-133 Medium quality hay 20-40 63-87 Good quality hay 27-31 55-74 Concentrates, pelleted 4-10 0-25 Finely ground oat straw 11-24 0-20 Finely ground hay 13 0-6