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GFP :0 > W8 - Lecture 22 - Grazing management 3 > Flashcards

W8 - Lecture 22 - Grazing management 3 Flashcards

1
Q

what is the DM of 100kg of grass grass

A

17kg of dry material
83kg of water

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2
Q

what are the components of cell wall

A

fibre
- NDF

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3
Q

what are the components of cell contents

A

sugars
oil
protein
minerals
other

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4
Q

what is the nutritive value of grazed grass

A

Energy (UFL/kg DM) - 0.85 - 1.05
protein (%) - 16-28%
NDF - 35-50%

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5
Q

What does high quality result in

A

high energy, high OMD
more digestible

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6
Q

what does poor quality result in

A

Low Energy,
Lower OMD
less digestibility

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7
Q

chemical compositions of grazed grass

A

crude protein: 180-250
NDF: 350-400
ADF: 180-250
WSC: 150-200

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8
Q

What does
- NDF
- ADF
- WSC
stand for?

A

NDF - Neutral Detergent Fibre
ADF - Acid detergent Fibre
WSC - Water soluble carbs

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9
Q

what is pasture quality influenced by: (8)

A

–> Soil fertility
➢ PGSHs
➢ Rotation length
➢ Herbage mass (pre grazing)
➢ Pasture species (% PRG, clover)
➢ Stage of growth
➢ Topping
➢ Season

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10
Q

how is pasture quality determined

A

organic matter digestibility - OMD

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11
Q

what is OMD use to calculate

A

the grass energy content - UFL/UFV value

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12
Q

what is high OMD

A
  • high UFL/UFV value
  • lower fibre, less filling - increased DMI
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13
Q

What is low OMD

A
  • Low UFL/UFV value
  • higher fibre, more filling - decreased DMI
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14
Q

how to calculate the % live leaf in a sward

A

take a range of grass samples from the
sward (cut to 4cm).
* 50 g sub sample.
* Divide sub sample
– live leaf
– vegetative material (stem/dead)
* Dry both samples in a microwave oven.
* Weigh the dried samples.

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15
Q

calculating the live leaf % in a sward

A

Example
- Dried sample of live leaf = 6.5g
- Dried sample of all other material = 2.5 g
- Total weight = 9.0 g
- Live leaf as a percentage of total weight is 72%

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16
Q

in autumn grass what is the
DMD%
UFL
CP

A

DMD% - =80%
UFL = 0.85-.90 UFL/kg DM or about 85/90% that of spring grass
CP - 21-23%

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17
Q

how much DM intake can autumn grass support a daily MY of 17.5 (23.5 kg in the summer)

A

16kg DM intake of autumn grass

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18
Q

what is the components of autumn (sept-oct) grass in lyons

A
  • CP 21-23%
  • 17.7kg DM intake of autumn grass only, can support 15.1kg milk
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19
Q

what happens when there is reduced pasture availability and poorer pasture quality

A
  • NDF and ADF increases
  • organic matter digestibility reduces
20
Q

what are the seasonal factors that effect herbage quality (4)

A
  • autumn pasture having a low DM content,
    – greater proportion of dead material,
    – slower rumen breakdown,
    – a lower energy value due to lower WSC and higher cell
    wall lignification compared to pasture grown in spring and
    summer
21
Q

what is the average value of well managed spring grass

A

DM - 16.4
OMD% - 85.6
ENERGY (UFL) - 1.05
NDF g/kg DM - 42
CP g/kg DM - 21

22
Q

what is there a change in as % leaf decreases

A

the chemical composition of grass

23
Q

what does pre grazing herbage mass influence

A
  • DMI
  • milk production performance
24
Q

what is the pre grazing herbage mass and rotation length

A

low = < 1100-1200 kg DM/ha (14.5 days )
Medium = 1300 - 1500 kg DM/ha
(20.3 days)
High = >2000kg DM/ha (29 days)

25
Q

what is the pre grazing herbage mass on grass nutritive value

A
  • CP% reduces from spring - Summer - Autumn

ADF% increased from spring - summer - autumn

  • UFL/kg DM decrease from S-S-A

Potential UFL intake/day decreased from S-S-A

26
Q

what does grazing swards with medium pre grazing yields
resulted in

A
  • higher grass utilisation
  • better sward quality
  • higher leaf content
  • which is reflected in higher overall production
27
Q

what are the components in a grazing sward

A

Pseudostem
leaf
dead material
true stem

  • differing digestibility values
28
Q

what is the PRG vegetative structure

A

very short true stem - 3cm

29
Q

what does the pseudo stem consist of

A

leaf sheaths

30
Q

what will happen if you graze pastures older than 3 leaves per tiller

A

result in both the wastage of the herbage and an increase in the senescent material which will reduce the nutritive value of the herbage

31
Q

what are the effects of sward digestibility on DMI and animal performance (3)

A
  1. Different levels of PGSH created the different levels of digestibility in the April to June period
  2. Swards were evaluated in the late summer to autumn periods using Spring-calving dairy cows
  3. Milk production in latter half of lactation.
32
Q

4 points for high sward OMD - Summary

A
  1. Increases DMI
  2. Increase milk yield
  3. Reduces time spent grazing
  4. Improves the ability of sward to be grazed out well
33
Q

what are the 3 distinct periods that the grazing season can be divided into

A
  1. autumn/winter
  2. spring
    3, main grazing season
34
Q

what is the main aim for the autumn/winter (august to december) grazing season

A

Aim: maximize grass utilization Sept-Dec while finishing the grazing season with the desired farm grass cover

35
Q

what is the target grass covers over the Autumn/Winter period depend on

A

Target grass covers over this period depend on:
➢ SR and demand:
✓ cow numbers
✓ milk yield potential
✓ level and type of supplementation
➢ autumn N application

36
Q

when should N be applied for Autumn/winter

A

Nitrogen application in July/ August/ September

37
Q

what should rotation length be in Autumn/ Winter

A

Rotation length should be increased from 21d in mid/late August to 30-35d in late Sept

The final grazing rotation of the year should be 40 to 45 days in length and resting of paddocks should begin from October 1 to 10 (varies from farm to farm)

38
Q

in autumn/winter, what should you avoid in the last rotation

A

Avoid excessively pre-grazing yields >2200 kg DM/ha in last rotation

39
Q

what do very high pre grazing yields lead to (Autumn/Winter)

A
  • poor utilisation
  • poor pasture quality in spring
40
Q

autumn grazing targets

A

slide 38

41
Q

what should the closing farm grass cover in late November be

A

550-600kg DM/ha @ 2.5 LU/ha.
- 1st paddock closed 900kg DM/ha
- Last paddock closed 200kg DM/ha

42
Q

why should pastures be grazed well in the final rotation

A

encourage autumn/winter tillering

43
Q

what is the aim for the max residual grass yield in paddocks as they are closed

A

Aim for a max residual grass yield of 100 kg DM/ha (4.5cm) in paddocks as they are closed

44
Q

when should paddocks be started to be closed

A

Start closing paddocks from the 10th October onwards (1-2 weeks earlier in wet areas)

45
Q

what % of the farm should you have closed off by the first week in November

A

60%

46
Q

what is the 60:40 autumn grassland plan based around

A

The 60:40 autumn grassland plan is based around these basic autumn grazing targets and guidelines. The plan ensures the farm will reach the 60% grazed target by the start of November

47
Q

what 3 pieces of information is needed for the 60:40 autumn grassland plan

A
  1. the area available for grazing
  2. the date on which the last round starts (target 10th October)
    3, the date the cows are full time housed

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