Ruminant Physiology Flashcards
Special features of ruminants
- able to utilize forages other mammals cannot digest
- forestomachs
- esophageal and reticulo-omasal groove to bypass rumen
- no upper incisors or canine teeth (dental pad)
Members of ruminant class
- cattle
- sheep
- goats: low fiber, discriminant/browser
- camelids (pseudoruminant)
Location of forestomach
- rumen/reticulum is on the left side
- omasum is in the middle
- abomasum is on the right side
Advantages
- break down cellulose to usable nutrients
- allows synthesis of high biological value protein: low biological plant protein, non-protein nitrogen, nitrogenous end product (urea)
- production of all B vitamins
Disadvantages
- regular food intake at regular intervals
- long hours chewing: food ingestion (4-7 hrs/day), chewing cud (8 hrs/day)
- keep rumen fermentation vat balanced: large quantities of alkaline saliva, constant mixing, release of gas products
Rumen layers
- gas
- fiber mat/raft
- fluid slurry (small particles)
Roughages
Cellulolytic
- cellulose: glucose
- hemicellulose: xylose
- pectin: galactose
Legumes
Cellulolytic
- able to fix nitrogen (high protein)
Grains
Amylolytic
- starches
- simple sugars
Requirements for fermentation
- regular addition of fresh food
- presence of suitable microbes
- steady removal of end products: gas, VFA, simple compounds, undigestible material
- continuous mixing
- propulsion of fine particles and fluid
- anaerobic
- stability: temperature, osmotic pressure, redox and pH
Protozoa
- live in fiber mat
- very sensitive to change
- feed on bacteria, plant starch and PUFAs
- provide high biological value protein
- prefer pH of 6.2
10^10 bacteria/gram rumen content
Cellulolytic bacteria - pH of 6.2 Amylolytic bacteria - pH of 5.8 Lactobacillus spp. - takes over at pH <5.8 - lactic acid producing (creates rumen acidosis)
Rumen dysfunction
- normal rumen pH 5.5-7.0
- rapid feed changes
- oral antibiotics
- die off of normal rumen fauna
Rapid feed changes cause
- acute acidosis/grain overload: pH < 5.0
- subactue acidosis/SARA: pH < 5.5
- takes 2 weeks for rumen fauna to adjust
Products of fermentation
- gases: methane (CH4 and CO2) is eructated
- volatile fatty acids: absorbed across rumen wall
- microbial and protozoal protein and lipids: passed thru to abomasum
- ammonia: absorbed across rumen wall
Volatile fatty acids
- acetate: ketogenic
- butyrate: ketogenic
- propionate: glucogenic
- ketone bodies: acetone, acetoacetate, betahydroxybutyrate
Is glucose available for absorption?
NO
- blood glucose levels in ruminants is lower
- insulin is lower
Acetic acid
- minimal liver use
- oxidized throughout most of the body to generate ATO
- major source of acetyl CoA for synthesis of lipids
Proprionic acid
- major liver use: removed from portal blood by liver
- serves as a major substrate for gluconeogenesis
- critical to the ruminant because almost no glucose reaches the small intestine for absorption
Butyric acid
- comes out of the rumen as the ketone beta-hydroxybutyric acid
- oxidized in many tissues for energy production
How long does it take to fast a ruminant
24-48 hrs of no food, 12 hrs no water
High fiber diets produce more _____
Acetate and butyrate
- higher butterfat in milk
High grain diets produce more ______
Proprionate
- higher milk volume but lower butterfat
Protein metabolism
Broken down to simplest form (ammonia)
- deamination of plant proteins
- urea from diet and saliva
- may feed up to 30% urea in diet (NPN)
- utilization of urea requires adequate energy in form of VFA or starch
Gas production
Up to 40 L/hour 204 hours after a meal
Green house gases
- water vapor, carbon dioxide, methane, nitrous oxide, and ozone
- carbon dioxide, CH4, and N2O
- fossil fuel combustion, iron and steel prodution, cement manufacturing and municipal solid waste combustion
Methane makes up _____ of green house gases
7.9%
_______ has decreased, but milk production has increased 4 x per cow
Number of dairy cows
- working on feed additive to decrease methane
Rumen motility/rumination
- mixes rumen fermentation vat continuously
- allows for regular release of gas (eructation)
- allows for cud chewing: reduces particle size and increases saliva flow
- filters fluid and particulate matter thru to omasum and abomasum
Innervation of forestomachs
Parasympathetic - vagus, CN 10 - promotes rumination, cud chewing Sympathetic - thoracic ganglia to celiac - decreases motility Nervous cows - drip/drool saliva - decrease (increase/hypermotile) rumen contractions
Types of rumen contractions
- primary: mixing and cud chewing
- secondary: eructation
- primary and secondary: cud chewing with eructation
Reticulum
- catches solid material
- source of Hardware disease
- prevention via magnet
- other dietary indiscretions include: plastic bags, placenta, other
Omasum
- very fine particles
- large surface area
- absorption of VFAs, electrolytes and water
- minor fermentation
- regulates propulsion into abomasum
- episodic slow contractions independent of reticular contractions
Abomasum
- true glandular stomach
- pepsinogen and HCl secretion
- average pH 3
- motility present but not well defined in fundic area
- peristalsis of pyloric area at 6/minute
Differences in ruminants
- fasting for surgery
- blood glucose not as high (45-75 mg/dl)
Special features of calves
- are nonruminants at birth
- reticulorumen is undeveloped
- lack sucrase and secrete limited amylase
- cannot digest plant proteins, unsaturated fats
- dependent on milk sugars, glucose, milk protein and fat
- liquid diets composed of milk, milk replacers, fermented colostrum
- esophageal groove
Requirements for ruminal development
- establishment of bacteria in the rumen
- liquid in the rumen (water)
- outflow of material from the rumen (muscular action)
- absorptive ability of the tissue
- substrate
Development of rumination
- cud chewing has been observed at 7 days
- by 2 months the calf can be weaned
- by 4 to 6 months the rumen is fully functional
- by 9 months the rumen is the same proportion of body weight as adult
Esophageal groove closure
Milk bypasses rumen - goes to abomasum
- muscular groove seals rumen opening
- stimulated by suckling
- chemcially closed by sodium chloride solution, sugar solution, sodium bicarb
Ruminal drinkers
- failure of esophageal groove to close
- over feeding
- mismothering/starvation
- putrefaction of rumen contents
- treatment: modified feeding schedule, small amounts often, probiotics
Beginning rumination
- need fresh water to provide ample liquid for the rumen
- bacteria needed to produce VFA (early bacteria are aerobic, similar to adults by 2 weeks)
- substrate - volatile fatty acids (coarse material or high fiber placed in rumen have no effect on development) –> dilute solutions of VFA placed in rumen stimulate development
- development of the rumen wall and papillae depend on grain intake
Important points
- calves need access to drinking water
- offer small amounts high quality calf starter daily (1 cup replaced daily if not eaten)
Salivary glands
Major - parotid (3rd cheek tooth): serous - mandibular: mixed - sublingual: mixed Minor - buccal, lingual, palatine: mucous Production: lysozyme, no amylase Volume: up to 200 L/day (100-150)
Composition of saliva
Isotonic to plasma
- alkaline pH 8.1
- Na: 170 mEq/L
- K: 13 mEq/L
- HCO3: 48 mEq/L
- Cl: 11 mEq/L
- PO4
- nitrogen (77% as urea)
Functions of saliva
- moistens food/aids in deglutition
- buffers acid production in rumen
- provides nitrogen for microbial production of amino acids
- protects against protein deficiency
Do ruminants produce saliva with atropine?
Yes, continuously
Clinical issues
- high grain diets decrease cud chewing and salivation (decreases buffering)
- salivation issue with general anaesthesia
- nervous animals: excessive drooling
Problems with swallowing
- choke
- listeria: interferes with hypoglossal nerve
- trauma/fractures of jaw
- serious ECF, electrolyte and bicarb loss
Rumen
- fermentation
- absorption of VFAs, ammonia
Reticulum
- keeps large particles from entering omasum
- eructation and cud chewing
Omasum
- continues fermentation
- absorbs VFAs
Abomasum
- acid secreting for digestion
- true stomach
