- high UFL/UFV value - lower fibre, less filling - increased DMI

- Low UFL/UFV value - higher fibre, more filling - decreased DMI

W8 - Lecture 22 - Grazing management 3 Flashcards by Aideen Cooper

what is the DM of 100kg of grass grass

17kg of dry material
83kg of water

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what are the components of cell wall

fibre
- NDF

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what are the components of cell contents

sugars
oil
protein
minerals
other

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what is the nutritive value of grazed grass

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

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What does high quality result in

high energy, high OMD
more digestible

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what does poor quality result in

Low Energy,
Lower OMD
less digestibility

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chemical compositions of grazed grass

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

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What does
- NDF
- ADF
- WSC
stand for?

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

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what is pasture quality influenced by: (8)

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

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how is pasture quality determined

organic matter digestibility - OMD

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what is OMD use to calculate

the grass energy content - UFL/UFV value

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what is high OMD

high UFL/UFV value
lower fibre, less filling - increased DMI

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What is low OMD

Low UFL/UFV value
higher fibre, more filling - decreased DMI

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how to calculate the % live leaf in a sward

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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calculating the live leaf % in a sward

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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in autumn grass what is the
DMD%
UFL
CP

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

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

16kg DM intake of autumn grass

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

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

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

NDF and ADF increases
organic matter digestibility reduces

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

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

what is the average value of well managed spring grass

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

what is there a change in as % leaf decreases

the chemical composition of grass

what does pre grazing herbage mass influence

DMI
milk production performance

what is the pre grazing herbage mass and rotation length

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

what is the pre grazing herbage mass on grass nutritive value

- 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

what does grazing swards with medium pre grazing yields resulted in

- higher grass utilisation - better sward quality - higher leaf content - which is reflected in higher overall production

what are the components in a grazing sward

Pseudostem leaf dead material true stem - differing digestibility values

what is the PRG vegetative structure

very short true stem - 3cm

what does the pseudo stem consist of

leaf sheaths

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

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

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

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.

4 points for high sward OMD - Summary

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

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

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

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

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

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

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

when should N be applied for Autumn/winter

Nitrogen application in July/ August/ September

what should rotation length be in Autumn/ Winter

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)

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

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

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

- poor utilisation - poor pasture quality in spring

autumn grazing targets

slide 38

what should the closing farm grass cover in late November be

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

why should pastures be grazed well in the final rotation

encourage autumn/winter tillering

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

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

when should paddocks be started to be closed

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

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

60%

what is the 60:40 autumn grassland plan based around

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

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

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