Acidosis Flashcards
Rumen is aerobic or anaerobic?
Anaerobic
Normal rumen gas concentrations
-65% CO2
-27% CH4
-7% N
-0.6% O2
-0.2% H2
Normal rumen temperature
38 to 41 degrees C
Normal pH range vs Extreme pH range
Normal: 5.5-6.9
Extreme: 4.5-7.2
Microbiology of the rumen
- Bacteria, protozoa and fungi
- Methanogens
- Bacteriophages
“Most rumen microbes are ______ ______”
Obligate anaerobes
Particle associated microbial communities are…
- up to 75% of the populations
- have high enzymatic activity
Liquid associated microbial communities are….
- Up to 50% of microbes
- Utilize soluble nutrients
Epimural associated microbial communities are…
- Small portion
- More stable
- Facultative anaerobes
Characteristics of short chain fatty acids
- Major source of energy supply
- Production of SCFA releases ATP for microbial growth
- Difficult to measure production
Major short chain fatty acids
- Acetate
-Propionate - Butyrate
2 Forms of lactic acid
L-lactic acid
D-lactic acid
Predominant isomer in the rumen is….
L-lactate
Which lactate form increases with lower pH?
D-lactate
Is there more absorption of L-lactate of D-lactate?
L-lactate
Acid production is caused by…..
Fermentation of acid production in the rumen
How is acid neutralized?
- Buffering by saliva and feed
- Absorption
- Passage through the rumen
Subacute ruminal acidosis definition
Rumen pH depression between 5.2 and 5.6 for at least 3h/day
Acute ruminal acidosis definition
Rumen pH below 5.0
When form of acidosis is more serious?
Acute acidosis
Symptoms of acute ruminal acidosis
- Depression
- Off-feed
- Elevated heart rate
- Diarrhea
- Death, if not treated
Steps that lead to acidosis (9 steps)
1) increased cereal grain intake
2) increased growth rate of bacteria
3) increased VFA produciton
4) increased Strep. bovis growth rate
5) increased lactic acid
6) decreased lactic acid utilizers
7) increased lactobacillus species
8) stasis fermentation
9) metabolic acidosis
Affects of ruminal acidosis
- decreased aninmal welfare
- decreased ADG and carcass weight
- associates with other disorders (liver abscess)
- mortality
Causes of ruminal acidosis
- increased VFA production leading to decreased absorption and buffering
- excess grain or NFC in diet
- rapid increase in dietary content of NFC (feed change)
- insufficient dietary course fibre or fermentable forages
- insufficient rumen buffering due to inadequate chewing and salivation (forage particle size)\
- cattle sorting forage out of the diet
Factors that make highly fermentable diets
- grain content
- grain type
- processing of grain
Consequences of acute acidosis
- metabolic acidosis
- death (in severe cases)
- chronic poor performance
Types of bloat
1) free gas
2) frothy bloat
What is frothy bloat?
Gas produced from fermentation gets trapped in a stable foam formed by breakdown of legumes leading to a build up pressure in the rumen
What is free gas bloat?
Build up of gas int he rumen that can not escape due to a physical obstruction of functional problem
Microbial risk factors of frothy bloat
- Mucopolysaccharide production
- Creation of a viscous fluid preventing separation of gas
- Streptococci linked
Steps in liver abcesses caused by acidosis
1) deterioration of rumen wall form acid production
2) Bacteria from rumen invade systemic circulation
3) hepatic portal blood system transfers bacteria to lover
4) bacteria are localized in live and encapsulated, causing abcesses
Etiology for laminitis
- Decreased pH causes increased Histamine and endotoxins
- Histamin is absorbed and causes inflammation
- Translocation of histamine causes systemic inflammation
- Systemic inflammation causes arterial dilation and vasoconstriction, especially in the hoof
- Inflammation increases cell permeability and causes vascular seepage
Consequences of vascular seepage
- Edema causing pain
- Hypoxia
- Hoof corium degeneration
- Mechanical damage of hoof structures
Effects of inflammation on performance?
- Decreased DMI
- Decreased ADG
- Decreased feed efficiency
Strategies to mitigate ruminal acidosis
- Reduce fermentability
- Include dietary buffers
- Rumen fermentation modifiers
- Feeding management
Strategies to reduce fermentability
- reduce dietary starch
-increase fibre - increase byproducts
- increase fat
Dietary bufferts to mitigate ruminal acidosis
-Bicarbonate
- Calcium carbonate
Rumen fermentation modifiers to mitigate ruminal acidosis
- Ionophores
- Amylase inhibitors
- Essential oils
- Mono- and poly- clonal antibodies
- Direct fed microbes
Feeding management to mitigate ruminal acidosis
- Increased frequency
- Bunk management
- Avoid period of feed restriction
- Dietary adaptation
Factors leading to variation in daily feed intake
- Weather (winter storms)
- Missed feeding
- Poor ration processing (lots of fines)
- Stale/moldy feed
- Moving up to quickly
Causes of feeding management errors
1) Animals get hungry
2) Consume too much feed
3) Mild - severe sub-acute acidosis
4) repeat process over time causes chronic acidosis
Which bunk management reduces incidence of sub-acute acidosis?
Slick bunk
Prevalence of acidosis increases with….
Advancing days on feed
Management to reduce incidence of sub-acute acidosis
-Limit amount of feed intake increase in a 3 day period
- Never increase amount of feed at the same time you chance to a higher grain ration
- Use a step up feeding program
- Change to a higher grain ration at afternoon feeding
- Feed an ionophore
- Multiple daily feedings
