Basics of Ruminant Nutrition Flashcards
How much of a ruminants time is spent:
- grazing
- ruminating
- resting
1/3 of its time doing each
What is the capacity of the rumen?
200+ L
Where is the rumen located in the cow?
On the LHS
Describe the features/role of the rumen
Fermentation chamber – anaerobic
Rumen microbes (“bugs”)
Fibre mat – “home to the bugs” & traps foods
Describe the 4 layers of the rumen
Top = gas
Fibre mat
Intermediate zone
Bottom = Liquid zone
What are the different areas of the rumen
Dorsal sac
Ventral sac
Cranio-dorsal blind sac
Name the 4 contractions involved in the primary rumen cycle
- First reticular contraction
- Second reticular contraction
- Dorsal rumen contraction
- Ventral rumen contraction
Describe the movement of material during the first reticular contraction
Course material to dorsal sac
Describe the movement of material during the second reticular contraction
Fine material to cranio-dorsal blind sac
Fine material to omasum
Describe the movement of material during the dorsal rumen contraction
- Fine material from cranio-dorsal blind sac to reticulum
- Coarse material circled back to caudo-dorsal blind sac and up
- Some exchange with ventral sac
Describe the movement of material during the ventral rumen contraction
- Fine material circulated back to cranial blind sac and up
- Some exchange with dorsal sac
- Some fine material into cranio-dorsal blind sac
Describe the secondary cycle of rumen contractions
Dorsal rumen contraction
- gas cap pushed forward, and gas released up oesophagus
What is the ratio of primary and secondary rumen contractions?
Ratio 2 Primary : 1 secondary
What products are produced by rumen bugs?
VFAs
Methane
CO2
What is the function of VFAs
Absorbed by the cow and used to supply energy or for fat/glucose synthesis
Milk production is determined by which 3 factors?
- Genetics
- Nutrition
- Health
Why is genetic milk production potential rarely achieved?
Inappropriate nutrition
When formulating diets (and analysing them) we tend to use what order?
Dry matter intake
Energy
Protein
Minerals
Vitamins
What ‘activities’ may an animal be involved in that need to be accounted for when assessing diets
- Maintenance
- Activity
- Lactation
- Growth
- Pregnancy
How much does a ruminant eat if she is doing nothing?
2% - 2.5% of bodyweight e.g. 14 Kg for 700Kg cow
How much does a ruminant eat if she is lactating 1. 25L per day, 2. 50L per day?
~25 litres per day – 3% of Bwt ~ 21Kg for a 700Kg cow
~50 litres per day – 4% of Bwt ~28Kg for a 700Kg cow
How much does a 700Kg ruminant eat if she is at the start of the dry period?
12-14kg per da
How much does a 700Kg ruminant eat if she is in the last 3w of pregnancy?
11-12Kg
How much does a 700Kg ruminant eat if she is in the last few days of pregnancy?
8-10kg
List some factors that influence dry matter intake
Body weight & fatness – “fat cows eat less”
Milk yield “the more she milks the more she eats”
Stage of production cycle
Type of food (digestibility / rate of passage).
Palatability (mixed forages).
Access - feed barrier, electric fence etc.
Social factors e.g. bullying of heifers.
Stress / pain e.g lameness.
Rumen health - “the right bugs & healthy bugs”
Define Metabolisable energy
Energy available to the cow for metabolism - maintenance, growth, lactation and pregnancy
Describe what a “diet for M + 35 litres” means
This diet will support 35 litres production if a cow eats X Kg daily
When calculating Metabolisable energy what does it assume?
The animal has a healthy rumen and micrflora
What are the sources of energy in a diet?
Sugars and starch
Fibre
Fats
Protein
Compare long chain and short chain carbohydrates
Long chain – slowly fermented e.g. fibre
Short chain - fast fermentation e.g. sugars, starches
What type of carbohydrate ferments the fastest?
Sugars
What do the acids produced by microbial fermentation need to be buffered by?
Salivary bicarbonate and phosphate
What are the 3 fates of VFAs?
- Absorbed across the rumen wall
- Enter the Krebbs cycle -> energy
- Glucose synthesis
Describe fats and oils as energy sources
Fats and oils are concentrated sources of energy compared to carbohydrates
Only practical value in diets for high yielding cows when DMI fails to meet energy requirements
Where are fats and oils absorbed in the body?
Small intestine
After calving, when is peak lactation?
Around 8 weeks later
Peak lactation corralates with?
Lowest body weight of the year
What is the main problem surrounding lactation post calving?
Her intakes struggle to match up to her yield in the first couple of months
She often compensated by mobilising her body reserves -> weight loss
– gives her enough energy to meet her body needs
Depressed DMI in first week’s post-partum coincide with massive energy demand for milk production –> ??
Negative energy balance
What is the target for BCS loss during the start of lactation?
0.5 - 1 SC points
1 CS = around 50Kg
How can cows cope with lactation energy requirements?
Eat more – increase her DMI
Metabolise body tissues - Fat & muscle
Reduce milk yield
Rumen degradable protein is any compound containing?
Nitrogen
Describe fermentation of rumen degradable protein
Broken down to NH4+
Used by bugs to grow (protein synthesis)
Microbial protein digested in abomasum
Bugs require ENERGY (FME)
How does protein metabolism cause a high blood (milk) urea?
Insufficient ME
Excess rumen degradable protein
What is rumen undegradable protein, where is it digested?
Passes through rumen
Digested in abomasum and small intestine
e.g. soya
Why is diet formulation of protein a balancing act?
Supply enough energy for her production…but not cause SARA
Forage: concentrate balance
How can you maximise DMI in lactating cows?
- Maximise intakes in dry period
- Palatable diet – mixed forages
- Avoid SARA
- Avoid getting fat
- Comfy environment
- Adequate feed barrier
- Unsure positive social environment
What is the aim % of dry matter intake at peak yeild?
4%
How many Kgs of DM do you want a cow to consume in the dry period?
12-14kg
What is the DM % of the following:
- Clamp grass silage
- Maize silage
- Big bale silage
- Hay
- Straw
- Concentrates
- Clamp grass silage = 20-35%
- Maize silage = 30-35%
- Big bale silage = 30-35%
- Hay = 85%
- Straw = 85%
- Concentrates = 90%
What is the Metabolisable energy per Kg of DM of the following:
- Clamp grass silage
- Maize silage
- Big bale silage
- Hay
- Straw
- Concentrates
- Clamp grass silage= 10-12MJ
- Maize silage = 11MJ
- Big bale silage = 8.5-10.5 MJ
- Hay = 8-9MJ
- Straw = 5-6MJ
- Concentrates = 12.5MJ
