Grazing Fodder Crops

15th October 2018

Grazing Fodder Crops

After the difficult conditions this summer across the UK and Ireland many of us have tried growing fodder crops such as rape, kale or stubble turnips to graze through the winter. These brassica crops can be a nutritious low-cost feed source for both cattle and sheep over the winter period. Work completed by the Scottish Agricultural College has found that store cattle can achieve 0.9kg DLWG and store lambs can achieve 0.25 kg DLWG.

Brassicas should only make up a maximum of 70% of the dry matter intake of the animal per day so it must be supplemented with forage such as silage, hay or straw to keep the rumen healthy. As can be seen from the table below brassicas are very nutritious feed however they animals must be supplemented with iodine and phosphorus.

 

Crop

Estimated DM Yield (kg/ha)

DM%

Digestibility (D-Value)

ME (MJ/kg DM)

CP (% DM)

Kale

9,000

15-17

80

10-11

14-17

Stubble Turnips

6,000

12-15

85

10-11

17-18

Forage Rape

4,800

10-12

80

10-11

19-20

Rape/Kale Hybrid

6,000

12-15

80

10-11

18-19

 

strip grazingStrip grazing is required to make best use of the crop to increase utilisation and limit the intake of brassicas and ensure the correct supplementation of forage. The strip wire should be set up on the long axis of the field to prevent trampling and further improve the utilisation. The picture below shows an example of how a field should be set up for grazing. You do not want to bring machinery into the field during the winter so if you have not already placed the forage into the field for grazing make the most of the current dry spell and place them there now. If water is not already in place in these fields, ensure that this is also addressed now by putting water troughs in place. Then throughout the winter move the feed ring over the bales whilst shifting the fence. You will also want to make sure that the fence is not earthing and to use a powerful electric fence energizer. Animals also need a dry place to lay so it is important that they have a grass lay back that will allow this.

To estimate DM yield in the field you can use the cut and weigh method as when measuring grass. You can cut and weigh the crop from a 1m2 area and then use the sum below.

1m2 fresh weight kg X 10,000 = Fresh Weight per Ha
Fresh Weight per Ha X Predicted DM = Fresh Weight per Ha

e.g.4kg Stubble turnip from 1m2

40,000kg FW ha
40,000kg x 14% DM
5,600kg DM/ha
1m2 =0.56kg DM

This table then estimates how to calculate the daily requirements for animals, how much you would need to shift the fence by per day and the area required for 100 days feeding.

 

 

350kg Weanling

600kg Dry Cow

34kg Lamb

A-Livestock DMI (2% Liveweight)

7 kg

12 kg

1.02 (3% of liveweight)

B-Brassica requirement (70% of total DMI- A *70%)

4.9 kg

8.4kg

0.71kg

C-Number of Stock

40

40

150

D-Daily Brassica Requirement of stock (B x C)

196kg

336kg

106.5kg

E-Area required per day at 0.56kg m2 (D/kg DM m2)

350m2

600m2

190m2

F-Fence moved per day (E / length of feed face) 140m

2.5m

4.3m

1.4m

G-Area required for 100 days feeding ((100x E)/10,000)

3.5 ha

6 ha

1.9 ha

 

Stubble Turnips

Grazing brassicas is not suited to all stock types or fields. It is important the all the animals that are being selected for outwintering are healthy, have fully developed rumens, are not lactating and have good mouths if grazing turnips. Fields should be dry and have a grass lay back, so animals have a dry place to lay. Things you must be vigilant for during the outwintering period are listed below-

  • Trace element and mineral deficiencies
  • Nitrate poisoning
  • Bloat
  • Redwater
  • Photo-sensitation
  • Lameness

To overcome these issues, it important that animals are slowly introduced to the crop to avoid digestive upsets and have access to a good quality mineral supplement. If you are planning on outwintering stock on brassicas this winter, please speak to your nutritionist for further advice.

« Back to Soil and Grassland Management Blog