Rumen Characteristics and pH PDF

Rumen 2 - Rumen Characteristics, pH and Buffering https://www.ranker.com/list/funny-cow-puns/nathandavidson  1°Contraction Cycle 1. Biphasic (double) contraction of reticulum 2. Contraction of cranial sac and cranial pillar 3. Contraction of dorsal sac Crani...

Rumen 2 - Rumen Characteristics, pH and Buffering https://www.ranker.com/list/funny-cow-puns/nathandavidson  1°Contraction Cycle 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 Digesta can move into reticulum http://bvetmed1.blogspot.com/2013/03/ruminant- abdomen-lecture-157.html  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 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 Rumen Characteristics Normal capacity 100-225 L in cattle 10-25 L in sheep Rumen fill detected by tension receptors Volume of contents (solid, liquid, and gas) Weight Reduced rumen capacity during late pregnancy Highest energy demand Negative energy balance Pregnancy toxemia Pregnancy  R R Singleton, day 88 Non-pregnant ewe R R Singleton, day 140 Twins, day 140  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/9781486309504/978148630 9504/SEC8/F30 Stratification Gas Active fermentation = gas Particles float Fermentable fiber Undegradable fiber Fermentable fiber consumed Density increases Mostly undegradable fraction remains Dense & small particle size Moves into omasum Opening ~2 mm in cattle Particles must be smaller than opening Denser = faster transit  Stratification https://www.midwesternbioag.com/rumen-health/ Rumen Characteristics Temperature Normal body temperature (39 ) Rumen lavage – use warm water Large volumes of cold water ↓ temp pH Very important in maintaining a healthy rumen Normal pH ~6 to 7 < 5.5 = acidosis Varies with: Diet Feed processing Feed intake Time between meals Rumen pH: Diet High forage diet = pH 6.5-7.2 High concentrate diet = pH 4.9-6.0 Grain is high in starch Rapidly fermented Acid production VFA and lactic acid Grain promotes growth of bacteria that produce lactic acid Forage is fermented more slowly Fiber stimulates salivation and rumination Buffering Saliva pH ~8.2 Adaptation to high-concentrate diets Step-up rations in feed lot Rumen pH: Feed Processing Chopping & grinding reduces particle size Increases surface area Lowers rumen pH Increased fermentation rate Less stimulation of rumen epithelial receptors Less “rubbing” by fiber ↓ chewing and rumination J. Dairy Sci. 92: 1603–1615 ↓ salivation ↓ buffering https://hoards.com/article-24040-cows-care-about-size.html Rumen pH: Feed Intake Going from restriction to full intake Drops pH by ~1 full unit (e.g. 6.5 to 5.5) More substrate = more fermentation Feed withdrawal Including reduced/no intake during illness Reintroduce feed in a controlled manner Do not allow to gorge  Rumen pH: Time pH is lowest 3-4 hours after feeding Rapid fermentation of starch Then increases until next feed More frequent meals = less pH fluctuation J. Dairy Sci. 89:217–228. Abnormal pH Effects on motility Epithelial receptors detect low pH Send inhibitory signals to gastric centers https://www.bovinevetonline.com/news/veterinary- Effects on microbes education/post-mortem-grain-overload Low pH favours starch digesters Strep bovis and lactobacillus Lactic acid production Acute acidosis Damage to rumen epithelium Lactic acidosis https://jaguzafarm.com/support/understanding-lameness-in-cattle/ Sub-acute ruminal acidosis (SARA) Reduced efficiency Laminitis Liver abscesses https://www.askjpc.org/wsco/wsc_showcase2.php?id=cEZ2QW9kT3kvZnAvdFhIS0xoZThUUT09 Acidosis https://ruminantdigestivesystem.com/potential-challenges/dimensions-of-acidosis/ Testing Rumen pH Low-producing dairy herd SARA suspected Stomach tube Risk of saliva contamination Fluctuations Sensor bolus Given orally, stays in rumen Lasts 3-5 months Newer technology possibly 2+ years Records daily patterns Cost https://moonsyst.com/phmonitoring Buffering Acids constantly being produced during fermentation Buffering keeps pH relatively close to neutral Saliva Large amounts of HCO3- and phosphate buffers Carbonic anhydrase Enzyme in rumen epithelium CO2 + H2O H+ + HCO3- H+ absorbed into blood HCO3- stays in rumen Buffer Saliva Modifies rumen pH – buffering Nutrients for microbes Nitrogen recycling Anti-frothing properties Reduces surface tension Enzymes Pre-gastric esterase (calves) Fat digestion No salivary amylase https://www.flickr.com/photos/dwrubleski/6039909981 Saliva Characteristics Volume produced >10% of body weight (100-200 L/day) Varies with diet and feed processing Composition (production per day) 1100 g NaHCO3 350 g Na2HPO4 100 g NaCl 40 g nitrogen 34 g urea Osmolarity Measurement of dissolved solutes Drives H2O from high to low solute concentration https://i.stack.imgur.com/1XkaP.jpg Rumen Osmolarity Rumen normal ~280 mOsm/L Hypotonic (lower than extracellular fluid, 300 mOsm/L) ↑ after feeding Fermentation produces VFA = more solutes Movement of water Normally absorbed from rumen to blood Rumen < blood Acidosis = ↑ solutes (VFA & lactic acid)= ↑ osmolarity Rumen > blood Water moves into rumen from blood “Splashing” sound Dehydration Gas Production Product of microbial fermentation Anaerobic environment – no O2 Maximum occurred ~2-4 hours after meal Cattle 30-50 L/hour 400 L/day Eliminated by eructation 2° contractions Bloat can occur very quickly https://onpasture.com/2021/04/05/spring-pasture-bloat-prevention-and-cures/ Gas Composition CH4 – 25% CO2 – 65% Methanogens Decarboxylation Reduce CO2 and formic acid Acetate & butyrate Energy is lost when CH4 is produced Carbonic anhydrase Up to 16% of gross energy on high CO2 + H2O H+ + HCO3- forage diet Up to 8% on high concentrate diet More efficient Ionophores reduce CH4 production H2 used to form propionate instead Animals, 2021. 11:2871 Other Gases N2 – 7% O2 – 0.5% Used up rapidly by facultative anaerobes H2 – 0.2% H mostly as H+ ions in solution H2S – 0.01% Rumen Turnover Time required to replace rumen contents with an equivalent volume Fluid vs solid Fluid turnover Inputs: Saliva Drinking H2O movement across rumen wall Outputs H2O absorption (across rumen wall) Passage to omasum High forage = faster (3-7 times/day) High concentrate = slower (2-3 times/day) Mostly influenced by salivation and drinking Solid Turnover Rate of loss of solid material Factors: Feed digestibility Grain ~90%, forage ~50% Feed intake ↑ intake = ↑ rumen distension = ↑ motility ↑ motility = ↓ time for fermentation Particle size Smaller = less retention Turnover and Efficiency More turnover = more substrate for bacteria ↑ VFA production Increased microbial efficiency Potential reasons Favours faster-growing bacteria More protein produced More bacteria in exponential growth phase ↑ dilution rate = ↓ protozoa to eat bacteria Washed away with rumen contents