Sward height has been shown to be a good practical indicator for use in grazing management which will enable good grass utilisation and livestock performance. Sward height can be converted into the weight of grass in kilograms of dry matter per ha (kgDM/ha)also known as  cover or mass, this enables grass budgets to be calculated.

WHY MEASURE SWARD HEIGHTS/COVER?

Knowing how much grass you have and how it is changing will help you to make management decisions to:

·         Set the right stocking density

·         Put the right class of stock on to a field

·         Gauge how long a piece of grazing should last

·         Make the most of fertiliser applications

·         Take fields out of grazing rotations and into silage areas

·         Identify a potential shortfall in grass before animals/milk yields are affected

·         Decide whether supplementary feeding  at grass is necessary

 

MEASURING SWARD HEIGHT/COVER

Walk across a field in a W pattern you should aim to take at least 30 readings in each field.  Record them on the app screen as you go and it will work out the average.  Avoid gateways, hedgelines and any areas that are not representative of the field in general.  If the field has a definite split between wet and dry areas it is a good idea to measure them separately.  Measure to the top of the grass leaf with a sward stick or ruler – don’t measure stems and flower heads and don’t measure weeds. Follow manufacturer’s instructions with a rising plate meter- these are less accurate at low sward heights and  on steeply sloping ground.  

During the peak of growing season sward heights can change fairly rapidly so consider measuring twice a week. The calendar can be used to remind you when to measure again.

TOOLS TO MEASURE SWARD HEIGHTS/ COVER

 

Any tool that can measure height in cm can be used, including a sward stick, a rising plate meter, a ruler, walking stick, alkathene pipe or even your boots with a scale drawn up the side. For consistent results the same person should take measurements every time. With plenty of practice you will be able to make rough judgements by eye, but there is no real substitute for walking fields, looking at the sward and measuring sward heights.

 

By recording sward heights you will be able to improve the use of grass on your farm and optimise animal intakes and reduce grass waste.  Grazing at the recommended height/cover will prevent swards becoming stemmy and maintain sward tiller density and quality through the grazing season and produce high levels of livestock performance.

Aftermath swards will respond differently to grazing pressure than normal grazing fields. They must be conditioned by grazing to encourage tillering before sward height/mass guidelines can be applied.

 

 

DAIRY COWS SWARD HEIGHT GUIDELINES (CM) 

Livestock Type

Graze Period

Rotational

Continuous

Notes

 

 

Pre-graze

cm

Post-graze

cm

* Interval

days

 

cm

 

Lactating

Cows/ Bulling Heifers

Turn-out-May

10-15

6-7

16-20

6-7

Top to 5 cm if sward height is exceeded. Check your stock condition score and growth rate targets

 

June-July

12-15

7-8

20-24

7-8

 

Swards above target in May should be topped by early June

 

Aug-Sept

12-18

8-9

24-28

8-9

 

Oct-House

12-15

6-7

Variable

6-7

All early/mid lactation cows will need supplements at this time

Dry cows

 

NA

4-5

 

4-5

Note cow condition score

 

DAIRY COWS GRAZING COVER GUIDELINES (kgDM/ha) 

 

Livestock Type

Graze Period

Rotational

Continuous

Notes

 

 

Pre-graze

kgDM/ha

Post-graze

kgDM/ha

* Interval

days

 

kgDM/ha

 

 

Lactating

Cows/ Bulling Heifers

Turn-out-May

2400

1500

16-20

2000

Top to 5 cm if sward height is exceeded. Check your stock condition score and growth rate targets

 

June-July

2800-3000

1500

20-24

2200-2300

 

Swards above target in May should be topped by early June

 

Aug-Sept

3000-3200

1500

24-28

2300-2500

 

Oct-House

3000-3200

1500

Variable

2300-2500

All early/mid lactation cows will need supplements at this time

Dry cows

 

1500-1800

1500

 

1500-1800

Note cow condition score: for thin cows increase pasture mass

 

 

* Rotation interval given as a guide only, it may need to be varied.  Post graze sward height is the primary decision driver.  Pre-graze sward height and rotation interval give information to assess ‘paddock skipping’ and ‘buffer grazing’ in forward planning of grazing area.

          

BEEF CATTLE SWARD HEIGHT GUIDELINES (CM)

Livestock Type

Graze Period

Grazing after rest on un-adapted sward

Continuous

Notes

 

 

Pre-graze

cm

Post-graze

cm

 

cm

 

Lactating Suckler Cows/Bulling Heifers

T’out-May

10-14

5-6

5-6

 

 

June-July

12-15

7-8

7-8

 

 

Aug-Nov

12-15

8-9

7-9

Graze to 5cm with dry stock Nov/Dec

Dry Suckler  Cows

 

 

 

 

 

4

Note condition.  Increase to 5-6cm for thin cows; restrict grazing for fat cows

Growing/

Finishing Cattle

T’out-May

10-12

5-6

5-6

Increase by 1-2cm for finishing cattle through season

 

June-July

10-14

6-7

6-7

Sward height should be gradually increasing

 

Aug- Sept

10-15

7-8

7-8

 

Weaned

Stores

 

7-9

5

5-7

Increase by 1-2cm through season

BEEF CATTLE GRAZING COVER GUIDELINES (kgDM/ha

Livestock Type

Graze Period

Grazing after rest on un-adapted sward

Continuous

Notes

 

 

Pre-graze

kgDM/ha

Post-graze

kgDM/ha

 

kgDM/ha

 

Lactating Suckler Cows/Bulling Heifers

T’out-May

2400

1500

2000

 

 

June-July

2600-3000

1500

2300-2500

 

 

Aug-Nov

2700-3000

1500

2300-2500

Graze to 1500 kgDM/ha with dry stock Nov/Dec

Dry Suckler  Cows

 

 

1800

1500

1900

 

Note condition.  Increase mass for thin cows; restrict grazing for fat cows

Growing/

Finishing Cattle

T’out-May

2400

1500

2000

Increase mass for finishing cattle through season

 

June-July

2600-3000

1500

2300-2500

Sward mass should be gradually increasing

 

Aug- Sept

2700-3000

1500

2300-2500

 

Weaned

Stores

 

2200-2700

1500

1900

Increase mass to increase stock growth rates

 

 

SHEEP SWARD HEIGHT GUIDELINES (CM)

Livestock Type

Graze Period

Grazing after rest on

un-adapted sward

Continuous

Notes

 

 

Pre-graze

cm

Post-graze

cm

 

cm

 

Ewes and lambs

T’out-April

8-10

4-5

4

Provide supplementary feed until sward height reaches  4cm ( remember stock mineral requirements)

Aim for gradual increase if possible

 

May-wean

8-10

4-6

4-6

 

Dry Ewes

July Aug

 

 

4 plus

Increase from 4cm for Condition Score <3 if ewes need to gain weight

Pre-tupping

Sept-Nov

8-10

4-5

6-8

Note condition: restrict grazing for fat ewes

Weaned lamb for finish

July-Sept

10-12

5-7

6-8

Allow gradual increase. Check growth rates targets

Store lambs

July-Start of finishing period

4

4

4

Increase sward height from 4 to increase growth rate.

 

 

SHEEP GRAZING COVER GUIDELINES (kgDM/ha) 

Livestock Type

Graze Period

Grazing after rest on

un-adapted sward

Continuous

Notes

 

 

Pre-graze

kgDM/ha

Post-graze

kgDM/ha

 

kgDM/ha

 

Ewes and lambs

T’out-April

2000

1500

1750

Provide supplementary feed until sward mass reaches  1750 kgDM/ha ( remember stock mineral requirements)

Aim for gradual increase if possible

 

May-wean

2200-2400

1500

1800

 

Dry Ewes

July Aug

1700-1900

1500

1800

Reduce sward mass for Condition Score >3

Pre-tupping

Sept-Nov

1700-2100

1500

1900

Note condition: restrict grazing for fat ewes

Weaned lamb for finish

July-Sept

2100

1700

2400

Allow gradual increase. Check stock growth rates targets

Store lambs

July-Start of finishing period

1900

1500

1500

Increase sward height to increase lamb growth rate.

 

 

 

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IBERS, Grassland Development Centre: 01970 823026

E-mail: GDCstaff@aber.ac.uk, Web page: www.grassdevcentre.co.uk

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