The acreage of fodder crops like forage rape has skyrocketed this year. Farmers that felt they were going to be short of silage sowed the forage crops in August and September to boost winter feed reserves.

At that time, the focus was all about getting the crops in on time and getting a good germination and crop growth. Now it’s all about getting the best utilisation as possible.

Growth rates are very good for the time of year so many of these forage crops are still growing well. Soil temperatures are around 12.5°C on average which is about 2.5 degrees above the long term average.

So the longer the crops are left in the ground the higher the yield will be. As things stand, yield is a bit of a mixed bag, with some crops looking very well at around 3t DM/ha, and others a lot lighter at scarcely more than 1.5t DM/ha.

When it comes to harvesting, there are three main options. The first is to graze it in situ. Animals should be introduced to brassica crops slowly, over the space of a week. Do this by gradually increasing the area being allocated per day. Roughage such as silage or hay should be available at all times.

To know how much to allocate you must know the yield of the crop. Cut and weigh a meter by meter section of the crop. Estimate the dry matter content of the crop (most forage rape is around 12% dry matter). Multiply the dry matter by the weight and multiply by 10,000 to get the dry matter yield per hectare.

The next thing you need to know is how much to give the animals. When the animals are fully adjusted to the forage crop, one third of their diet on a dry matter basis should be from silage or hay but when they are getting adjusted to the crop, two thirds of the diet should be silage or hay and only one third provided by the crop.

Generally speaking cattle will eat 2.5% of their liveweight per day. So 450kg in-calf heifers will eat around 11.25kg DM per day. When they are fully adjusted they should be eating 7.5kg of crop and 3.75kg of silage per day.

Multiply the number of animals by the desired feeding rate and divide into the cover to work out how much area to feed per day. So if you have 35 heifers eating 7.5kg of crop the daily demand is 263kg of crop.

Divide the yield in kg/ha into 10,000 to work out how many square meters per one kg of feed and multiply this by the daily demand to get the daily allocation in meters square.

For example, 10,000 divided by 3,000 equals 3.33. So 3.33 multiplied by 263 equals 877 meters square. Long and narrow allocations are better than short and deep. Work out the width of the strip and divide this into 877 to work out how deep you should go. Remember that animals will reach in under the wire to graze so include about 1m back from the fence in the allocation.

The important thing is to look at the job the animals are doing and adjust accordingly. If they are constantly hungry you are not allocating enough. If they are leaving silage and crop behind you are allocating too much. A dry area to lie back on is essential.

Silage

Other farmers are using the fine weather to get their brassica crops cut for silage. Because the dry matter of these crops is very low, the silage needs to be very well wilted before being picked up.

The forecast for most of the country is fairly good this week so a good wilt should be possible. You are really talking about cutting the crop with a mower conditioner and leaving the crop down for two days to wilt.

High yielding, early sown crops with good stalks will need extra film wrap to protect the bales from stalks protruding out and puncturing the wrap.

Move bales as soon as possible after wrapping to the storage site as they are likely to sag after being baled and wrapped.

Zero grazing

Other farmers have started zero grazing brassica crops. This is a relatively new phenomenon as the proliferation of zero grazing machines has increased a lot. The thing to remember from a feeding perspective is that feeding zero grazed brassica crops is the same as grazing and the animals need to be built up on to brassicas slowly with the same ratio of silage to crop as with grazing brassica crops.

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