Yield assessment and grazing management of Mainstar forage brassica - Elders Rural Services
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Yield assessment and grazing management of Mainstar forage brassica

Mainstar is a highly palatable forage brassica, which has quickly increased in popularity over the last couple of years.

A key point of difference when compared to older forage brassica (rape) types, is Mainstar’s animal acceptance, which results in enhanced levels of utilisation. Mainstar has a high leaf to stem ratio and a softer, more grazable stem, which helps drive higher daily intakes and improved animal performance.

To maximise the longevity and animal productivity from your Mainstar crop, AusWest SPS have put together the following tips to help graze and measure the crop.

Yield estimation

Yield estimation is essential to developing your Mainstar feeding program, as it will tell you how many animals the crop can carry and how long these animals can graze.

To do this, get a 3.55 m length of poly-pipe and create a circle (this will be 1m2) and pick an area in the paddock at random. Place the pipe circle on the ground and cut the plants off at ground level. Put the plants into an old seed bag and weigh the fresh weight. Typical dry matter content of brassica can vary from 12 to 24 per cent (pc), so either dry down a sample yourself or send a sample away to be dried to help with the calculations, then use the following equation to work out how much feed is on offer:
(Fresh wet weight of crop in 1m2) x (dry matter %) x 10,000 = kgDM/ha.
Note: This step needs to be repeated three times per hectare to get an average that represents the whole paddock.

Once you have worked out how much feed is in the paddock, you need to work out how long the paddock will last. For example, if the 10 ha Mainstar crop yield is 5,500 kgDM/ha and there are 500 lambs grazing the crop, how long will the crop last them?

Lambs grow best when allocated 2 to 2.5kgDM/hd/day, so using this number we can work out the following: 5,500 kgDM/ha x 10ha / (500 X 2.25) = 48 days.
Based on these calculations this crop should last approximately 48 days. If you split this paddock into four equal sized breaks, the lambs would need to be shifted every 12 days.

By back-fencing the crop youare letting the grazed areas grow without disruption for an extra 36 days, meaning the regrowth will be stronger than if the paddock was set stocked for the 48-day period. Back-fencing gives more control of the quality of feed the lambs get over the whole grazing period. Set stocking loads the diet with high quality at the start and lower quality towards the end as lambs start getting into the stem.

Grazing management

Maximising production from your Mainstar crop involves back fencing (or rotational grazing), adequate water supply and moving animals on to the next break before they have over grazed the current allocation.

Mainstar’s palatability means stock can graze it to the ground. To maximise the opportunity for regrowth, you need to move stock on to their next break, or paddock before this occurs. The ideal grazing residual is when 10 to 15 cm of the stem is remaining with all leaf and most of the petiole removed.

The photo above show lambs grazing a Mainstar crop, with still enough leaf and petiole left for the lambs to remain in the paddock for a further three to five days. Ideally you should set up your paddocks, so the lambs are being shifted onto fresh feed every 10 to 14 days.

After grazing

Once your Mainstar forage crop is coming to the end of its life, start thinking about how you want to get that paddock back into grass. Ideally it should be grazed off quite short, allowed to freshen, then sprayed out before planting.

One option for autumn succession planting is Mohaka AR37. This new tetraploid hybrid ryegrass has similar winter activity to Italian ryegrass, but more longevity. Its late flowering date enables areas with early summer rainfall to carry high quality tetraploid feed through into early summer. Mohaka AR37 should last two to four years, and is an ideal mix partner with herbs and legumes, such as Ecotain® environmental plantain, Choice chicory and Relish red clover.

Article written by Hamish Best, Agricom, AusWest & SPS National Product Development Manager for Seasons magazine. 

Mainstar is available from your local Elders store. Order now.

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