Ruminant digestion and metabolism Flashcards
What does herbivore fermentation reliant on to digest cellulose and other plant material?
- micro-organisms within the GIT
What species use mainly foregut fermentation?
- ruminants
- hippopotami
- camelids
What species use mainly hindgut fermentation?
- horses
- rabbits
- elephants
How long does fermentation take?
- takes a long time with slow passage and high volume
Herbivore fermentation relies on a constant environment - what makes the constant environment?
- continuous food intake, matched with the outflow - break in this can lead to issues
- pH regulation (bicarbonate in saliva) - 200 L saliva
What are the three phases in cellulose degradation?
- complex sugars are converted to simple sugars by extracellular microbial enzymes
- simple sugars are converted to pyruvate by intracellular microbial enzymes (through glycolysis)
- pyruvate converted by intracellular microbial enzymes to
- volatile fatty acids
- gases
Pyruvate is converted by intracellular microbial enzymes to volatile fatty acids - what are the VFAs and describe them?
- Acetate (60-70%) - increases with roughage - 2 carbon
- Propionate (15-20%) - increases with concentrates - 3 carbon
- butyrate (10-15%) - 4 carbon
Pyruvate can be converted by intracellular microbial enzymes to gases - what are these gases and how much gas can a cow produce an hour?
- carbon dioxide (CO2)
- Methane (CH4)
- up to 30L/hr/cow
What is the underlying cause for primary ketosis?
- cause is usually nutritional
What is primary ketosis?
- unable to take in enough metabolizable energy to meet metabolic demand
Describe primary ketosis in pregnant cows and how it can be corrected:
- rumen becomes smaller due to calf taking up room = negative energy balance
- can increase amount of concentrate, increasing the amount of propionate and therefore glucose
- more cows would go down with this type of ketosis
What can lead to secondary ketosis?
- another disease / anything that reduces feed intake
- depression
- lethargy
- mastitis
- metritis
- lameness
- LDA
- bullying
What is the pattern for secondary ketosis that can aid in diagnosis?
- usually sporadic and can be pinpointed to something else other than diet
What is pregnancy toxaemia or twin lamb disease?
- sheep with multiples = shrink rumen - cant take in enough energy to lead to growth, sheep uses own reserve to feed lamb
What does pregnancy toxaemia cause an increased demand for?
- increased demand for glucose but due to multiple foetuses drawing on glucose across the placenta
What is the solution to pregnancy toxaemia?
- boost glucose intake
- caesarean
- prevention is better than treatment
Is all dietary protein digested in the rumen?
- no some of the dietary protein passes through the rumen and is digested in the abomasum and small intestine
How can ammonia be used by rumen microbes?
- ammonia can be used by the rumen microbes to make new amino acids which also become part of microbial protein
Other protein is digested into amino acids in the rumen - what can these do?
- incorporated into microbes
- deaminated (taking the amino off) generating VFAs and Ammonia
What can be used by the ruminal microbes to manufacture amino acids?
- non-proteinaceous nitrogen (urea)
What happens when microbes pass through the rumen into the rest of the GIT?
- digested enzymatically releasing amino acids which are absorbed into the body
By utilising urea and microbes what can ruminants therefore do?
- can make their own essential amino acids and thrive on a low protein/poor quality protein diet
What helps to manufacture vitamins that can be absorbed in the small intestine?
- microbes
What is the difference between fore and hind gut digestion processes?
- Fore - ingesta leaves the rumen and enters abomasum (=monogastric stomach) and intestines, digested and absorbed similar to monogastric
- whereas hind fermentation occurs after conventional digestion so limited absorption of fermentation products
What are fermentation products?
- VFAs
- microbial protein
- vitamins
In hindgut fermenters what cannot be utilised as well when compared to foregut fermenters?
- cannot use microbial protein as there is no way of absorbing this is LI
- vitamins (not fat soluble)
In hindgut fermenters what is the alternative way to absorb VFA’s?
- VFA merge with cell wall and can be absorbed that way
What type of diet do hindgut fermenters need in comparison with foregut extensively managed ruminants?
- need a higher quality diet in comparison
What does bloat normally look like?
- abnormally enlarged rumen or ruminal tympany
Were does bloat usually start and how does it progress?
- usually starts in the left paralumbar fossa as this is where the gas cap sits
- progresses to ventral distention
- then right sided distension = squishing
What are the two types of bloat?
- free gas bloat
- frothy bloat
What is free gas bloat?
- anything that prevents eructation of gas
What is frothy bloat?
- gas forms a stable foam, small bubbles so cannot eructate
In free gas bloat what causes the prevention of eructation and what can this look like?
- recumbent cow or lateral recumbency
- oesophagus is below fluid level so cannot eructate
- fluid blocks cardia so cannot eructate
In free gas bloat what can cause the physical obstruction to the oesophagus?
- actinomyces Bovis lumpy jaw
What can cause free gas bloat?
- lack of motility in the rumen/reticulum
- tetanus
- hypocalcaemia
- rumen acidosis
- damage to vagus nerve (vagal indigestion)
What causes frothy bloat?
- bubbles of gas coalescence that doesn’t from a proper gas bubble
In frothy bloat - grain overload/ feedlot bloat can be a cause - what is this?
- high level grain diets
- also associated with rumen acidosis
- finely ground grains more likely
What can grain overload sometimes cause?
- free gas bloat
pasture bloat (leguminous bloat) can also be a cause of frothy bloat - what forages can cause this?
- soluble protein in some forages causes foaming
- lush pastures
- clovers
- alfalfa
How can you treat free gas bloat?
- release the gas by passing a stomach tube to push obstruction through
- or pass trocar and cannula into the rumen via the left paralumbar fossa
What treatments are NOT successful for frothy bloat?
- stomach tube or trocar and cannula unsuccessful
- very small amount of froth released and rumen distention is NOT relived
What treatment can be used to treat frothy bloat?
- anti-foaming agents = release surface tension allowing gas bubbles to coalesce and gas can then be eructated
How can bloat be prevented?
- pasture management
- do not feed finely ground cereals
- at least 40% forage in the diet
How can bloat cause internal damage?
- everything gets displaces
- starts to push diaphragm and puts pressure in the aorta
What is LDA?
- displacement of the gas-filled, distended abomasum to the left side of the abomasum, trapping it between the rumen and the abdominal wall
What is a RDA?
- displacement of the gas -filled, distended abomasum from the ventral abdominal wall into the craniodorsal right abdominal cavity
What is an abomasal volvulus (torsion)?
- displacement of the gas filled, distended abomasum from the ventral abdominal wall into the craniodorsal right abdominal cavity, secondarily creating a volvulus by vertical and horizontal rotation (abomasum, wrapped in the greater omentum) leading to a risk of necrosis
What can cause LDA or RDA?
- cow has decreased feed intake
- energy deficient
- ketone levels in the blood rise
- ketosis
What is ketosis?
- build-up of ketone bodies in the blood
What causes ketosis?
- caused by a negative energy balance and fat loss (loss of BCS) which produces ketones
What do ketones do to the cow?
- makes the cow feel unwell, so she eats even less
How can you diagnose ketosis?
- high levels of ketone bodies in the blood or urine
- beta-hydroxybutyrate
What is the difference between primary and secondary ketosis?
- Primary = underlying cause is usually nutritional
- secondary = due to another disease
What does fatty liver result from?
- results from a state if negative energy balance one of the most important metabolic diseases of post parturient dairy cows
When does fatty liver usually develop?
- before and during parturition
What contributes to the development of fatty liver?
- periparturient depression of feed intake and endocrine changes associated with parturition and lactogenesis contribute to the development of fatty liver
What cows are at a higher risk of fatty liver?
- cows that are over conditioned at calving are at higher risk
What causes the development of fat within liver tissues?
- due to the NEFA’s being processed here and there is too much FA because the body cannot shift where it has to go
What is fat cow syndrome a combination of?
- metabolic, digestive, infectious and reproductive conditions which affect the obese periparturient cow
What are clinical signs of fat cow syndrome?
- depression
- anorexia
- ketonuria
How can you prevent fat cow syndrome?
- feeding a balanced diet
