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
What adverse heath effects are linked to SARA
- Displaced abomasum
- Ketosis
- Lameness (sub-acute clinical laminitis)
- Mastitis (dirty cows)
- Infections
When diagnosing SARA what clues may be lead to this being higher on the differentials
Fertility
Lameness
Ketosis
LDA
Faeces
‘‘Odd sick cows”
When observing a group for suspected SARA what should you observe?
Cudding
Rumen fill
Tail swishing
Dirt score
Condition Score
How can faeces be examined to help diagnose SARA?
Score 1- 5
Sieve faeces
Describe sieving faeces for SARA diagnosis
- Sieve faeces under running water.
- Fibre should be less than ½” long.
- No or little undigested grain.
- Fibre over 1.25cm long.
- Undigested grains.
- Mucus casts
What do mucus casts indicate?
Colon inflammation
Describe how you would measure rumen pH
- herd test
- take 2 samples, 4 hours after feeding
- restrain cow (nose and tail)
- clip and scrub
- LA
- 3 – 5” needle – 16G – 18G.
- Read sample immediately
Where is the site to insert the needed to gain a rumen sample
Level of stifle & 6 – 8” behind last rib
Describe which cows you would collect from for rumen sampling within a herd
- Cows calved 14-21d ago: assesses transition and early diet
- Cows calved 60-80d ago: assesses overall diet quality
- Sample from both groups, 6 cows from each
- Diagnosis confirmed when 2 cows from either group are below the pH threshold
Describe which cows you would collect from for rumen sampling within a herd
- Cows calved 14-21d ago: assesses transition and early diet
- Cows calved 60-80d ago: assesses overall diet quality
- Sample from both groups, 6 cows from each
- Diagnosis confirmed when 2 cows from either group are below the pH threshold
What happens if fibre is cut too long?
Cows will sort it from the total mixed ration
What is the maximum ratio of concentrate : fodder you would want your cows to have?
60:40 max
Grass silage quality depends on what factors?
- Grass type
- First or second cut
- Time of day - pm best for sugars
- Moisture content
- Chop length
- Compaction in clamp
- Fermentation
List some factors of maize silage as a feed
- High energy 11 – 11.5 ME
- High starch – fermentable metabolisable energy
- Low protein (8 – 9%)
- Fibre: Short & pulverised
- Ineffective as source of long fibre - So feed straw with it
List some features of concentrate feed
High FME
High proteins
No fibre
What is a disadvantage of parlour cake feed linked to SARA
Parlour cake fed reduces intake of TMR and thus fibre
Is acute ruminal acidosis an individual or herd problem?
Can be individuals
Describe the pathophysiology of acute ruminal acidosis
- Excessive acid production
- pH falls below 5.0
- Lactic acid production predominates
- “Lactic acid eating bugs” killed off
- Cow cannot metabolise ‘d’ lactate
What type of diet leads to acute ruminal acidosis?
Overeating grain - barley poisoning
Sudden introduction of high levels of grain
How is acute ruminal acidosis diagnosed?
Often a group problem
Will see varying degrees of severity - From mild ataxia to recumbency and shock
What are the clinical signs of acute ruminal acidosis?
- Distended rumen - bloat
- Ataxia
- Diarrhoea: profuse and smelly
- Depression
- Recumbency and shock
How can you treat mild acute ruminal acidosis?
Give hay to eat and observe
How can you treat sub-acute ruminal acidosis?
Oral antacids
- Magnesium hydroxide or carbonate (500g),
- Feed hay
How can you treat per-acute ruminal acidosis?
Rumenotomy – empty rumen contents
5 litres 5% sodium bicarbonate i/v
Continue with balanced fluids for 12 – 24 h
How can you prevent acute rumen acidosis
- Close the door on the food store !!
- Care with introduction of grain to fattening animals
- Good fibre source
- Correct mixing of diets
Describe a rumenotomy procedure
- Lifesaving – emergency surgery
- Recumbent animal
- 18” incision at least
- Pack towels around
- Open rumen and empty of all contents
- Not a sterile operation !!!
