With the appropriate management, several grazing brassica crops offer second and even third grazing opportunities for cattle and sheep, allowing extended grazing that can reduce pressure on winter feedstocks. With two or three grazings from a single crop, the strategy also means establishment costs are spread across significantly increased dry matter yields, cutting the cost per tonne.
Crops suitable for multiple grazing currently available include the grazing turnip Appin, which is suitable for use through into November, and the cold-tolerant hybrid brassicas Swift and Redstart that can be used for out–wintering. If soil fertility and pH levels are correct, these crops are easy to establish and fast-growing.
“Forage brassicas have traditionally been seen as a single grazing crop in the UK, but our experience in other parts of the world with some of the newer varieties shows that a multi–grazing strategy is perfectly possible,” says Helen.
“Once the crop is well established and reaching the top of your wellies, take an early and light grazing. The key management point is to leave a good 10cm of stem, with plenty of nodes from which new growth will develop. This is best achieved by dividing the field into four and grazing each block for five to seven days – possibly less depending on growth rates – and then starting back in block one. If strip grazing with cattle it may be advisable to use a back fence to protect the regrowth.
“In hungry soils, where the first blocks have been grazed by the end of July, there is an option to top dress with nitrogen.
“Assuming your original crop has provided in the region of 3–4,000 kgDM/ha of available fodder, you can expect around 75% (2,500kgDM/ha) from a second grazing, and then as much as 60% (2,000kgDM/ha) from a third grazing in some cases.
“Bearing in mind that the only additional cost is the fertiliser, your overall cost/kg of dry matter is going to be cut by a minimum of 40–50% by adopting a multi–graze strategy.”
Helen Mathieu says that multi–grazing is an effective way of extending the grazing season and can be used with all classes of ruminant livestock, including dairy cows, but is a particularly effective method of fattening lambs.