Basics of Ruminant Nutrition Flashcards

1
Q

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

A

1/3 of its time doing each

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2
Q

What is the capacity of the rumen?

A

200+ L

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3
Q

Where is the rumen located in the cow?

A

On the LHS

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4
Q

Describe the features/role of the rumen

A

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

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5
Q

Describe the 4 layers of the rumen

A

Top = gas
Fibre mat
Intermediate zone
Bottom = Liquid zone

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6
Q

What are the different areas of the rumen

A

Dorsal sac
Ventral sac
Cranio-dorsal blind sac

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7
Q

Name the 4 contractions involved in the primary rumen cycle

A
  • First reticular contraction
  • Second reticular contraction
  • Dorsal rumen contraction
  • Ventral rumen contraction
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8
Q

Describe the movement of material during the first reticular contraction

A

Course material to dorsal sac

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9
Q

Describe the movement of material during the second reticular contraction

A

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

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10
Q

Describe the movement of material during the dorsal rumen contraction

A
  • 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
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11
Q

Describe the movement of material during the ventral rumen contraction

A
  • Fine material circulated back to cranial blind sac and up
  • Some exchange with dorsal sac
  • Some fine material into cranio-dorsal blind sac
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12
Q

Describe the secondary cycle of rumen contractions

A

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

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13
Q

What is the ratio of primary and secondary rumen contractions?

A

Ratio 2 Primary : 1 secondary

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14
Q

What products are produced by rumen bugs?

A

VFAs
Methane
CO2

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15
Q

What is the function of VFAs

A

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

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16
Q

Milk production is determined by which 3 factors?

A
  • Genetics
  • Nutrition
  • Health
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17
Q

Why is genetic milk production potential rarely achieved?

A

Inappropriate nutrition

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18
Q

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

A

Dry matter intake
Energy
Protein
Minerals
Vitamins

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19
Q

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

A
  • Maintenance
  • Activity
  • Lactation
  • Growth
  • Pregnancy
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20
Q

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

A

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

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21
Q

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

A

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

22
Q

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

A

12-14kg per da

23
Q

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

A

11-12Kg

24
Q

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

A

8-10kg

25
Q

List some factors that influence dry matter intake

A

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”

26
Q

Define Metabolisable energy

A

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

27
Q

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

A

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

28
Q

When calculating Metabolisable energy what does it assume?

A

The animal has a healthy rumen and micrflora

29
Q

What are the sources of energy in a diet?

A

Sugars and starch
Fibre
Fats
Protein

30
Q

Compare long chain and short chain carbohydrates

A

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

31
Q

What type of carbohydrate ferments the fastest?

A

Sugars

32
Q

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

A

Salivary bicarbonate and phosphate

33
Q

What are the 3 fates of VFAs?

A
  • Absorbed across the rumen wall
  • Enter the Krebbs cycle -> energy
  • Glucose synthesis
34
Q

Describe fats and oils as energy sources

A

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

35
Q

Where are fats and oils absorbed in the body?

A

Small intestine

36
Q

After calving, when is peak lactation?

A

Around 8 weeks later

37
Q

Peak lactation corralates with?

A

Lowest body weight of the year

38
Q

What is the main problem surrounding lactation post calving?

A

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

39
Q

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

A

Negative energy balance

40
Q

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

A

0.5 - 1 SC points
1 CS = around 50Kg

41
Q

How can cows cope with lactation energy requirements?

A

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

42
Q

Rumen degradable protein is any compound containing?

A

Nitrogen

43
Q

Describe fermentation of rumen degradable protein

A

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

44
Q

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

A

Insufficient ME
Excess rumen degradable protein

45
Q

What is rumen undegradable protein, where is it digested?

A

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

46
Q

Why is diet formulation of protein a balancing act?

A

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

47
Q

How can you maximise DMI in lactating cows?

A
  • Maximise intakes in dry period
  • Palatable diet – mixed forages
  • Avoid SARA
  • Avoid getting fat
  • Comfy environment
  • Adequate feed barrier
  • Unsure positive social environment
48
Q

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

A

4%

49
Q

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

A

12-14kg

50
Q

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

A
  • Clamp grass silage = 20-35%
  • Maize silage = 30-35%
  • Big bale silage = 30-35%
  • Hay = 85%
  • Straw = 85%
  • Concentrates = 90%
51
Q

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

A
  • 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