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.
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 |
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 GDC, Plas Gogerddan, Aberystwyth, Ceredigion, SY23 3EB
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