Managing brassicas for successful outwintering

Wednesday 20.10.2021 , news

Brassicas are more than just a catch crop. They provide a flexible, cost-effective, nutritious option for outwintering livestock, reducing the need for winter housing and bought-in feed. But good management is essential. We answer some common questions about brassica management and hear from two farmers using them successfully.

Can brassicas help to maintain growth rates and stock performance?

Brassicas are an ideal crop to use for outwintering as they are high in protein and energy, supporting performance without the need for bought-in concentrates.

Chris Ruffley, Assistant Farm Manager at Harper Adams University uses Maris Kestrel kale to outwinter all his in-calf dairy heifers: “Since starting to outwinter on Maris Kestrel kale we haven’t looked back. The animals do better outside in terms of growth rate and health; we’ve achieved growth rates of 1.29kg/day.”

In South Lanarkshire, Andrew Baillie outwinters his suckler cows on Maris Kestrel kale and Triumph swedes, as well as finishing his pedigree rams for sale on stubble turnips: “Many buyers comment on how active and fertile the forage-finished rams are when sold. Rams leaving my farm for another grass or forage-based system don’t suffer the same checks and drop-off in performance they would if accustomed to a concentrate-based diet. So, as well as saving money on concentrate, we are also producing a better product. It’s a win-win situation.”

How cost effective are brassicas for outwintering?

Outwintering on brassicas can reduce both housing and associated labour costs over winter, as well as feed costs by minimising the need for bought-in concentrates.

“We started using a range of alternative forage crops about eight years ago and they have helped us reduce winter feed costs dramatically,” explains Andrew. “It used to cost us 98p a day to feed cows over the winter period but now it’s down to 22p. Our concentrate feed use for all our ewes has also dropped from 22-23 tonnes a year, to just five tonnes.”

How do I measure a brassica crop?

Careful assessment of dry matter yield is important to optimise productivity and plan feed requirements accurately:

  1. Within a 1m2 area use garden shears to cut each plant to around 10-15cm from the ground
  2. Weigh the cut crop in a bag
  3. Repeat this across several 1m2 plots which are representative of the crop and take an average
  4. Multiply the average fresh weight by the expected dry matter percentage
  5. Multiply this figure by 10,000 to give the dry matter yield per hectare

Table 1 Expected dry matter percentage by crop

Crop

Dry matter yield (kg/ha)

Dry matter (%)

Swedes (eg. Triumph)

9-14,000

10-12%

Kale (eg. Maris Kestrel)

11-12,000

12-15%

Turnip (eg. Appin, Vollenda)

6,500

9-12%

Hybrid Brassica (eg. Swift, Redstart)

7-10,000

12-14%

How much of the diet should be grazed brassicas?

Brassicas should not make up more than 70% of the dry matter intake, and only 30% in lactating cows. Therefore, it is important to provide an additional source of fibre such as hay, straw, or silage.

“For supplementary fibre we feed haylage alongside the kale, as we’ve found this is the most cost-effective option,” explains Chris.

How do I calculate the amount of brassica to allocate each day?

Understanding a crop’s dry matter percentage helps determine crop allocation and how much the fence is moved each day when strip grazing. Through careful planning and accurate allocations, strip grazing can help to achieve 85-90% crop utilisation. As a rule of thumb, animals outwintering need a daily dry matter intake equivalent to at least 2.5% of their bodyweight. This is higher for youngstock and their requirements increase as they gain weight over the grazing period.

Table 2 How to calculate crop allocation based on a 270kg weanling requiring 8kgDM/day

 

Requirement

1.      Estimated livestock total intake

8kgDM/day

2.      Percentage of grazed brassicas

70%

3.      Brassica daily requirements (1. x 2.)

5.6kgDM

4.      Number of livestock

25

5.      Daily requirements from brassicas (3. x 4.)

140kgDM

6.      Estimated crop DM yield/m2*

0.8kgDM/m2

7.      Total daily grazing area required (5. ÷ 6.)

175m2 of brassica

8.      Length of feed fence

120m

9.      Fence to be moved (7. ÷ 8.)

1.5m/day

*Based on crop yields of 10tDM/ha (1kg/m2) x 80% utilisation

Do I need to supplement minerals when grazing brassicas?

Livestock grazing brassicas over winter need to receive supplementary minerals, particularly copper, selenium and iodine. These are given most effectively as a bolus but can be provided as licks or bags on bales.

“One of the most critical things when grazing brassicas is to avoid any mineral deficiencies, particularly iodine,” advises Chris. “We give a mineral bolus as this is the only health-related issue we find needs addressing. Overall, their health is much better when outwintering on kale.”

If the grazing period is very wet, should I move livestock to run-off areas at night?

Moving stock is more likely to increase the risk of poaching by concentrating the footfall on a narrow area. If animals are well fed, they should be content to stand and lie on drier, just grazed areas. And if there is more hay or straw than they need, they may lay on it.

For more information about managing livestock on brassicas over winter, CLICK HERE to check out our brassicas growers guide.

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