Although the winter fodder deficit has largely corrected itself over the last few weeks owing to the exceptional growth conditions in grassland swards, winter fodder crops remain an important winter feed for many livestock farmers.

Links forged with tillage farmers are mutually beneficial in that the livestock farmer gains feed, while nutrient rich dung is adeptly spread by the grazing stock.

Tullamore Farm has been using forage crops in recent years as part of the reseeding programme, alongside spring barely, with this year’s yield ahead by 0.5t/ac on the ground which was grazed by livestock in rape the winter previous, compared to the land not sown.

While they are of a huge benefit, livestock farmers need to exercise caution in their use, with some key advice detailed below on managing crops successfully.

Introduce brassicas slowly

Introduction to forage crops should take place on a phased basis. Allow stock to graze initial for one to two hours, before building up to full time access at day 10. Alternative fodder source to be available at all times.

Mineral supplementation

Brassica crops are low in essential minerals – namely, iodine, selenium, copper and cobalt. Animals must be supplemented with these minerals prior to grazing forage crops, with blousing being the surest way that animals receive adequate levels of each mineral.

Inclusion of fibre

Brassicas should not form any more than 70% of the diet. Grass lie-back areas can be used as alternative sources of feed, provided there is sufficient grass available to form the additional 30% of the animal’s diet. Where there is insufficient grass supplies, or the lie-back area comprises stubble land, then hay, straw or silage should be accessible to animals. Ideally, these bales should be spaced out prior to grazing and shortly after sowing to prevent the need for machinery to enter fields during the winter months.

Ensure access to fresh water

Despite their low dry matter (around 12%), grazing animals must always have access to clean, fresh water. It is important to consider trough position when allocating forage crops; it is not ideal that animals would continually have to travel over grazed ground to access crops, as this will lead to excessive poaching.

Grazing in-situ and allocation

The most suitable option is to graze the brassica crops in-situ, where infrastructure allows. A good electric fence and easy access to water are two critical points to consider.

Where lambs are being strip grazed, it may be necessary to use more than one strip wire, which will require a break to be established either through cutting or flattening the crop along the fence line.

Allocation

With the colder months, animals will require a higher percentage of their bodyweight, approximately 3%, when grazing outdoors. To ascertain how much forage crop should be allocated some simple calculations are required. Animal weight and numbers:

The next step is to calculate the volume of forage crop in the field. This is most accurately done by cutting and weighing.

Weight of crop in kg x 0.12 (dry matter percentage of rape) x 40,000 = tonnes DM/ha

eg 1.8kg x 0.12 x 40,000= 9.6t DM/ha

Assuming 30% of our animal intake is coming from silage/hay/straw, the above example of 40 weanling heifers will require 231kg DM of forage crops per day. Dividing our requirement (231kg) in to our supply (9.6t) we will have sufficient forage crop available for 41-42 days of grazing in a 1ha paddock and should be divided as such. Grazing days may increase through growth in the crop, but decreased with poor utilisation.

In relatively square fields, a good measure can be to count the number of fence posts along the length of a field and use this as a guide, eg 30 posts in a field at 4m spacing= 120m long, meaning the allocation should be approximately wide 3m/day. Dry matter percentage will be variable depending on crop type and the weather conditions.

Grazing in these narrow strips will avoid wastage and increased the amount of fresh feed being presented to animals. Depending on utilisation, allocations can be reduced or increased.

When allocating forage crops, ensure there is no frost present before giving animals a new strip as frost can increase the nitrate levels in forage crops, which can lead to nitrate poisoning.