Where there’s a will, there a way. For farmers, one of the ways of getting out of fodder troubles for this winter was to sow a forage crops. Redstart and kale were two of the most popular choices. While this is not an unusual method of foddering animals for winter and while it is something that many farms throughout the country are well used to, some farmers were forced into sowing brassicas for the first time this summer as silage making fell by the wayside.

Now that these crops are rapidly growing and grazing is just around the corner, these farmers may be still unsure about what out-wintering on these crops actually entails. For those farmers entering into the unknown, here is a quick guide through the management of both the crop and your animals’ health while grazing it:

First and foremost, it is important to play by the rules. In terms of catch crops and out-wintering, there are a few to remember. Firstly, when grazing catch crops animals need 1ha/LU of a lie-back area in order to meet cross-compliance regulations. As well as that, if sown under GLAS, the grazing of catch crops is not permitted until after 1 December.

Looking at grazing there are two main considerations; grazing method and supplementation requirements. When grazing a catch crop it should be strip grazed. Animals should be offered enough of the crop to feed them sufficiently for one day only. With this in mind, the most important decision to make when strip-grazing is the amount of fresh-matter offered to the herd each day or in simple terms, the size of the strip you allocate.

If the strip is too small, it can lead to underfeeding which, particularly if conditions are poor, may lead to a loss in performance or BCS.

On the other hand, a strip size too large will lead to overfeeding which may affect animal health (explained later) and poor utilisation.

The best plan is to measure a sample area of the crop using the cut-and-weigh method and then work out the DM/ha. Kale and redstart have a DM of about 16%. After this, it will be trial and error until you get it right. Secondly, supplementation on catch crops is key. Cattle fed a brassica crop such as fodder rape must also be fed a roughage source, otherwise they will be at risk of rumen acidosis.

Usually when feeding brassicas, two thirds of the diet is made up of the forage crop and the remainder is high-dry matter grass silage or straw. The decision to use straw or silage will depend on availability, but also on the allocation of the forage crop.

If the allocation is quite low relative to the requirement, silage will be needed to meet the energy requirements of the animal. For ease of management during the winter, place a line of silage bales across the field to match the manner in which the crop will be grazed.

This way, bales can simply be opened each time the fence is moved with minimal hardship.

Top tip

Always have a second fence up behind the one stock are grazing to. Firstly, if cattle break the first fence, they will destroy the crop if they are let roam the entire field. Secondly, if you go out on a very bad morning and cattle are anxious to move, it can be done quickly, keeping them (and you) happy.

Animal health tips

With the management of the crop explained, it is also important to remember the management of livestock grazing the crop. Journal vet Tommy Heffernan highlights six top animal health tips to be mindful of when grazing brassicas this winter:

Watching the weather

Cattle are well-adapted to wintering outside once they are in reasonable body condition and/or they aren’t facing any other health challenges. Making sure all parasite dosing is up to date before going onto winter crops is important. I’ve found parasite risk to be lower while on these crops but every farm must assess their own risk. If ground gets wet and mucky there can be some increased risk of lameness also. This only usually occurs where previous infections are present. If dosing cattle before turning out to these crops, it’s good to assess any lame animals and carry out treatments. Always have one eye on very adverse weather conditions because this might increase some of the risk for a lot of the issues I talk about here.

Supplement with iodine

The brassicas rape and kale are particularly low in iodine and also contain a compound which locks it up. My advice, if out-wintering pregnant animals is to give a high-quality, slow-release iodine bolus. As animals come within 6-8 weeks of calving it is advisable to take these animals off these feeds. The symptoms of an iodine dificiency can be seen most commonly in the calf, with stillbirths or weak calves.

Risk of bloat/CCN

When we introduce a new feed at any time, the rumen takes time to adjust (approximately two weeks). Brassicas in particular can then lead, particularly with heavy intakes, to a risk of bloat. It is suggested to feed some source of fibre, particularly for the first four weeks. As mentioned, two thirds of the diet should be brassicas and the other third a fibre source, such as silage. Also it is advisable to strip graze for a start to control intakes and not advisable to leave hungry animals straight out – this should be done anyway for grazing management, as already mentioned. Also when you have diet changes like this you need to be watchful for CCN, a vitamin B1 deficiency which causes meningitis-like symptoms.

Vaccinate against clostridial diseases

A lot of clostridial diseases are present in soil. Therefore, when certain conditions arise, this can be a risk. These vaccines are relatively cheap and require two shots. This is a good insurance policy to reduce the risk on winter crops, pre-turnout.

Nitrate poisoning

Another disease that we can reduce the risk of by slow introduction and adding fibre into the diet for the first four weeks is nitrate poisoning. Poisoning occurs when high levels of nitrites build up in the rumen. The symptoms are rapid breathing, tremors and weakness. In severe cases, the pink membranes of eyes and mouth can turn brown. Like any unusual clinical conditions you see, remove affected animals and add more fibre to the rest of the herd’s diet.

Anaemia on kale

Kale contains very high contents of SMCO, an amino acid which can cause anaemia (destruction of red blood cells). The symptoms can be like redwater (red urine from damaged red blood cells being present), because of the chemical reaction in the cattle’s body.

Be watchful for these, treatment usually involves removing the animals from the crop. Low phosphorous soils high sulphur and high nitrogen increase the risk.

Case study: Tullamore Farm

Last winter, kale was grazed on Tullamore Farm. In terms of grazing management, the fence was moved 1m per day, allocating 9kg DM to cows and 4kg DM to weanlings. Silage was allocated at a rate of 2kg DM/cow or weanling each day also.

Grazing conditions were good as ground conditions held up well. During periods of frost and snow, the strip wire wasn’t moved until kale had thawed. All stock had access to a lie back area, but they generally lay along the fence line where it was being grazed. Weanlings did minimal damage.

The only problem came during the severe weather at the end of February and early March as heavy snow fell. As a result, silage and meals were increased and animals were given access to more sheltered paddocks.