Sub-acute ruminal acidosis (SARA) Flashcards
Microbial fermentation of carbohydrates produces?
Volatile fatty acids
What substances are involved in rumen acidosis?
- Excessive concentrates
- Insufficient fibre
- D lactic acid: Cannot be metabolised so builds up
Rumen pH should be between?
6 - 7
What happens when the rumen pH is too low?
Kills bug populations
Encourages growth of lactobacilli - produce lactic acid which cannot be metabolised
Decreased efficiency of digestion
Undigested particles lead to osmotic diarrhoea
How does osmotic diarrhoea affect the colon?
Colon acidosis - damages colon wall - fibrin casts in faeces
Describe the steps involved in acidosis developing in the rumen
- Reduced saliva flow and rapid carbohydrate digestion
- Lead to decreased rumen pH
- Carbohydrate digestion decreases, energy yield from digestion decreases
- Microbial activity falls, lactic acid producing microbes increases
- Lactic acid production
List the factors that affect the rumen pH
- How much acid (VFA’s) produced.
- Type of acid produced – lactic acid = strong
- Rate of fermentation.
- Rate of acid removal (across the rumen wall - papillae)
- Buffering by saliva – chewing the cud.
How is the rumen wall and papillae growth affected by dry cow nutrition?
Dry cow nutrition & transition diet:
- Encourages papillae growth
- Get the “right bugs”
How does a low pH affect the rumen wall and papillae?
Low pH – destroys papillae – rumenitis
“Vicious cycle”
SARA bout predisposes to another SARA bout
When is saliva produced?
When chewing long fibre - cudding
What buffering substance does saliva contain?
Sodium bicarbonate
What % of cows in a herd should be cudding at one time?
70%
Why is long fibre important in the diet?
- Encourages cudding - Bicarbonate buffers acid
- Forms a rumen mat
- Keeps food particles in rumen to be digested
- Home to the bugs: biofilms
List the risk factors for SARA
- insufficient long fibre in the diet
- inaccurate DM estimation
- overmixing of total mixed ration
- excessive feeding of sugars and starches
- poor dry cow management
- food deprivation and irregular feeding
- poor cow comfort
Is SARA a herd or individual problem?
Herd - 30% of animals at risk
- nutritional disorder
- overall poor health
If an animal has SARA how will their faeces appear
Loose and soft
Will see undigested grains
Will see them swishing tails due to sore bums
What are the effects of SARA on a cow
- Reduced DMI
- Reduced digestibility (NEB)
- Immunosuppression -> increased diseases susceptibility
- Poor yields
- Reduced milk quality
- Adverse health effects
- Reduced fertility