Kale is being successfully utilised as an out-wintering crop for in-calf dairy heifers at Harper Adams University. While cost savings are important in this scenario, it should not come at the expense of animal health as Katie Jones discovered.
In-calf dairy heifers at Harper Adams University have been successfully outwintered for a number of years, using forage rape, stubble turnips, and in 2019/2020 a catch crop on kale.
Chris Ruffley, assistant farm manager at Harper Adams, explains that last season the outwintered in-calf heifers achieved an average daily liveweight gain (DLWG) of 1.29kg.
And he adds that those heifers, which went onto the crop from grass, also avoided the growth check often seen around housing.
Costs
In terms of costs, Mr Ruffley reckons the crop of kale costs around 50p/head/day, which represents a saving when compared to feed costs at housing of around 拢1.20/head/day.
This year Maris Kestrel kale has been grown as a main crop on a nine hectare (22-acre field) to support about 50 spring calving heifers. Mr Ruffley says he hopes they will once again achieve good growth rates.
This year's crop was drilled at the end of May following a wheat crop. Farmyard manure was applied to the wheat stubble, which was then subsoiled and disked before drilling.
"We let the crop get growing and then applied a small amount of inorganic nitrogen, before going in with separated slurry liquor applied via a 12m dribble bar. The crop has been sprayed for flea beetle but no herbicides were required."
Method
Mr Ruffley explains that the headlands were seeded down to grass, which the heifers went onto first before slowly being introduced to the kale itself.
He adds the relatively light land is expected to stand up well to the outwintering, but he adds it is important to get infrastructure right.
Because the field is in close proximity to residential housing the boundaries have been fenced, and bales of haylage placed to offer the heifers some long fibre to the diet.
Helen Mathieu of Germinal Seeds says it is important that a decent source of fibre is used as the kale is low in fibre. "It needs something to hold the kale in them", she says.
"They need some structure in the diet. It is important to keep the rumen going."
The heifers at Harper have free access to haylage with bales placed to provide a new one every one to two days when the electric fence is moved with timing depending on how quickly the kale is cleared.
Dry matter
It is estimated the Holstein heifers, which weigh around 450kg will consume 10kg of dry matter (DM) a day from the kale, and a further 4-5kg DM of haylage.
Mr Ruffley says: "The heifers were introduced slowly so that they got used to grazing the crop, and taking it right down to the ground straightaway."
Ms Mathieu reinforces the importance of letting the cattle get used to the brassica slowly to begin with.
She says: "They need some time to let their rumen adapt to it, so it is important to limit access to start with, before gradually building up to a full allocation."
She adds that care should also be taken when it comes to mineral supplementation as kale is low in copper, selenium, iodine, vitamin E, phosphorous and magnesium. It is also high in calcium and potassium.
She says: "It does depend on the stock grazing the brassica, but the low copper status can be a deficiency issue in cattle, particularly in late gestation.
"Brassicas may also contain higher levels of sulphur which will challenge the uptake of copper."
She adds that the low selenium may also compromise iodine status and brassicas are also low in iodine.
Supplement
To counter this it advised that cattle have a mineral supplement. The heifers at Harper received two mineral boluses before going onto the brassica.
Ms Mathieu says the kale will carry on growing until soil temperatures drop below 10 deg C. She adds that the brassica is very winter hardy and is not particularly affected by frosts.
The field will go into maize next year, and Mr Ruffley expects that as long as ground conditions do not get too wet the field will just need flat lifting again before the seed bed is prepared for drilling.
Helen Mathieus tips for outwintering cattle on kale
- Have a plan B to allow for bad weather. "The health of the animal, and the soil, is paramount."
- If you are thinking about outwintering, set your stall out early. A crop of kale must be drilled by at least the end of June. Plan the fencing for feed-out to allow a fresh beak every day and think about access to water.
- Consider a semi-dwarf variety like Maris Kestrel. She says this will still grow to 鈥榟ip height', with good leaf to stem ratio. "You do not want a tall variety which can make it more difficult to move the wire, and also lead to problems with the wire tripping."
