Crop choice for livestock grazing brassica and forage crops

Crop and livestock performance will vary between farms and even field to field. Knowing which crops are suitable for your system should help lead you to success.

Crop selection should be based on:

• Soil type
• Number and type of stock
• When the land becomes available (e.g. after first cut silage or stubbles after cereals)
• Suitability within the crop rotation
• When the crop will be fed

Summary of sowing and feeding times for a range of crops

Note: sowing date will vary based on location, with areas in the south being able to sow earlier in the spring and sow later in the autumn

There can be considerable variation in performance between different varieties. Before buying, look into:

• Yield (specifically usable yield)
• Disease resistance
• Digestibility of stems/bulbs/leaves
• Leaf-to-stem ratio
• Regrowth ability
• Winter hardiness
• Growing height
• Versatility

Brassicas, including kale, grazing turnips, stubble turnips and rape/kale hybrids are suitable for feeding to most classes of cattle and sheep.

Some varieties of grazing turnips and rape/kale hybrids can offer multiple grazing opportunities when drilled early in summer and managed appropriately. However, this can involve back fencing and applying fertiliser, so it may not be applicable depending on your farm’s location and NVZ restrictions.

You should also ask for a forage variety, as some varieties of brassicas, especially kale, have been selected for use as game cover and have a greater proportion of stem, making them less suitable for grazing.

The most suitable brassicas for grazing during winter are kale, swedes and rape/kale hybrids.

Stubble turnips, grazing turnips and forage rape are better as summer catch crops or for extending the grazing season at the end of the year, as they are less winter hardy.

Brassicas should be grown once every four to five years (in drier areas) or seven to eight years (in wetter areas) to minimise disease risks.

When feeding, brassicas should provide 50–70% of the livestock dry matter intake. Overfeeding can reduce intake and performance, with health problems such as iodine deficiency (goitre) and anaemia becoming a risk. 

The energy level of brassicas is on a par with high-quality conserved forages but lower than that of cereals and concentrates. The crude protein content of leafy brassicas is high, 14–20%, although it is much lower in root crops such as swedes. They have a high, readily digestible carbohydrate content but are low in fibre, which is why they should be fed with a fibre source such as straw or hay to prevent rumen acidosis or bloat.

Remember, average DM yield is based on crops with optimum levels of nutrients and good agronomy. If in doubt, measure the crop in field, plan feeding accordingly and re-adjust costings.

Swedes are only recommended for cattle with fully mature teeth and are not suitable for broken mouthed sheep.

Ewes in late pregnancy fed on root crops will generally need additional protein to ensure their feed requirements are met.

When used for finishing lambs, supplement root crops with sources of dietary protein and leafy crops with additional energy.

Fodder beet is a higher input crop that can be lifted and fed elsewhere or grazed in situ. There is considerable variation in performance between different varieties.

Fodder beet crops require monitoring for the proportion of leaf to bulb within the crop. The leaf contains 25% of the dry matter but most of the protein, calcium and phosphorus. The bulb tends to be 75% of the dry matter but low in protein. If there is low leaf cover, then supplement with grass to supply protein and minerals and maintain intakes. Fresh allocation of the crop also encourages high intakes. 

AHDB research has found that heifers outwintered on fodder beet had higher milk protein than heifers outwintered on grass or kale, lower milk fat, but milk yields were not affected. 

If you would like to order a hard copy of Using brassicas for Better Returns or the Home-grown forages guide, please contact publications@ahdb.org.uk or call 0247 799 0069.