Basics of Ruminant Nutrition

Question 1

How much of a ruminants time is spent:
- grazing
- ruminating
- resting

Answer 1

1/3 of its time doing each

Question 2

What is the capacity of the rumen?

Answer 2

200+ L

Question 3

Where is the rumen located in the cow?

Answer 3

On the LHS

Question 4

Describe the features/role of the rumen

Answer 4

Fermentation chamber – anaerobic
Rumen microbes (“bugs”)
Fibre mat – “home to the bugs” & traps foods

Question 5

Describe the 4 layers of the rumen

Answer 5

Top = gas
Fibre mat
Intermediate zone
Bottom = Liquid zone

Question 6

What are the different areas of the rumen

Answer 6

Dorsal sac
Ventral sac
Cranio-dorsal blind sac

Question 7

Name the 4 contractions involved in the primary rumen cycle

Answer 7

• First reticular contraction
• Second reticular contraction
• Dorsal rumen contraction
• Ventral rumen contraction

Question 8

Describe the movement of material during the first reticular contraction

Answer 8

Course material to dorsal sac

Question 9

Describe the movement of material during the second reticular contraction

Answer 9

Fine material to cranio-dorsal blind sac
Fine material to omasum

Question 10

Describe the movement of material during the dorsal rumen contraction

Answer 10

• 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

Question 11

Describe the movement of material during the ventral rumen contraction

Answer 11

• Fine material circulated back to cranial blind sac and up
• Some exchange with dorsal sac
• Some fine material into cranio-dorsal blind sac

Question 12

Describe the secondary cycle of rumen contractions

Answer 12

Dorsal rumen contraction
- gas cap pushed forward, and gas released up oesophagus

Question 13

What is the ratio of primary and secondary rumen contractions?

Answer 13

Ratio 2 Primary : 1 secondary

Question 14

What products are produced by rumen bugs?

Answer 14

VFAs
Methane
CO2

Question 15

What is the function of VFAs

Answer 15

Absorbed by the cow and used to supply energy or for fat/glucose synthesis

Question 16

Milk production is determined by which 3 factors?

Answer 16

• Genetics
• Nutrition
• Health

Question 17

Why is genetic milk production potential rarely achieved?

Answer 17

Inappropriate nutrition

Question 18

When formulating diets (and analysing them) we tend to use what order?

Answer 18

Dry matter intake
Energy
Protein
Minerals
Vitamins

Question 19

What ‘activities’ may an animal be involved in that need to be accounted for when assessing diets

Answer 19

• Maintenance
• Activity
• Lactation
• Growth
• Pregnancy

Question 20

How much does a ruminant eat if she is doing nothing?

Answer 20

2% - 2.5% of bodyweight e.g. 14 Kg for 700Kg cow

Question 21

How much does a ruminant eat if she is lactating 1. 25L per day, 2. 50L per day?

Answer 21

~25 litres per day – 3% of Bwt ~ 21Kg for a 700Kg cow
~50 litres per day – 4% of Bwt ~28Kg for a 700Kg cow

Question 22

How much does a 700Kg ruminant eat if she is at the start of the dry period?

Answer 22

12-14kg per da

Question 23

How much does a 700Kg ruminant eat if she is in the last 3w of pregnancy?

Answer 23

11-12Kg

Question 24

How much does a 700Kg ruminant eat if she is in the last few days of pregnancy?

Answer 24

8-10kg

Question 25

List some factors that influence dry matter intake

Answer 25

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”

Question 26

Define Metabolisable energy

Answer 26

Energy available to the cow for metabolism - maintenance, growth, lactation and pregnancy

Question 27

Describe what a “diet for M + 35 litres” means

Answer 27

This diet will support 35 litres production if a cow eats X Kg daily

Question 28

When calculating Metabolisable energy what does it assume?

Answer 28

The animal has a healthy rumen and micrflora

Question 29

What are the sources of energy in a diet?

Answer 29

Sugars and starch Fibre Fats Protein

Question 30

Compare long chain and short chain carbohydrates

Answer 30

Long chain – slowly fermented e.g. fibre Short chain - fast fermentation e.g. sugars, starches

Question 31

What type of carbohydrate ferments the fastest?

Answer 31

Sugars

Question 32

What do the acids produced by microbial fermentation need to be buffered by?

Answer 32

Salivary bicarbonate and phosphate

Question 33

What are the 3 fates of VFAs?

Answer 33

- Absorbed across the rumen wall - Enter the Krebbs cycle -> energy - Glucose synthesis

Question 34

Describe fats and oils as energy sources

Answer 34

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

Question 35

Where are fats and oils absorbed in the body?

Answer 35

Small intestine

Question 36

After calving, when is peak lactation?

Answer 36

Around 8 weeks later

Question 37

Peak lactation corralates with?

Answer 37

Lowest body weight of the year

Question 38

What is the main problem surrounding lactation post calving?

Answer 38

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

Question 39

Depressed DMI in first week’s post-partum coincide with massive energy demand for milk production --> ??

Answer 39

Negative energy balance

Question 40

What is the target for BCS loss during the start of lactation?

Answer 40

0.5 - 1 SC points 1 CS = around 50Kg

Question 41

How can cows cope with lactation energy requirements?

Answer 41

Eat more – increase her DMI Metabolise body tissues - Fat & muscle Reduce milk yield

Question 42

Rumen degradable protein is any compound containing?

Answer 42

Nitrogen

Question 43

Describe fermentation of rumen degradable protein

Answer 43

Broken down to NH4+ Used by bugs to grow (protein synthesis) Microbial protein digested in abomasum Bugs require ENERGY (FME)

Question 44

How does protein metabolism cause a high blood (milk) urea?

Answer 44

Insufficient ME Excess rumen degradable protein

Question 45

What is rumen undegradable protein, where is it digested?

Answer 45

Passes through rumen Digested in abomasum and small intestine e.g. soya

Question 46

Why is diet formulation of protein a balancing act?

Answer 46

Supply enough energy for her production…but not cause SARA Forage: concentrate balance

Question 47

How can you maximise DMI in lactating cows?

Answer 47

- Maximise intakes in dry period - Palatable diet – mixed forages - Avoid SARA - Avoid getting fat - Comfy environment - Adequate feed barrier - Unsure positive social environment

Question 48

What is the aim % of dry matter intake at peak yeild?

Answer 48

4%

Question 49

How many Kgs of DM do you want a cow to consume in the dry period?

Answer 49

12-14kg

Question 50

What is the DM % of the following: - Clamp grass silage - Maize silage - Big bale silage - Hay - Straw - Concentrates

Answer 50

- Clamp grass silage = 20-35% - Maize silage = 30-35% - Big bale silage = 30-35% - Hay = 85% - Straw = 85% - Concentrates = 90%

Question 51

What is the Metabolisable energy per Kg of DM of the following: - Clamp grass silage - Maize silage - Big bale silage - Hay - Straw - Concentrates

Answer 51

- 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