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Making quality silage for sheep


The guideline silage requirement for the average lowland ewe is 0.15 tons pit silage/ewe/month or 0.19 bales/ewe/month. Damian Costello, Sheep Specialist Teagasc Athenry, discusses making quality silage for sheep, has tips for successful silage making and a link to a recent webinar on it here

Where ewes are winter housed silage feed value has been ranked as the third most important factor affecting profitability in mid-season sheep production (Keady and Hanrahan, 2006). Like many things making good silage is all about attention to detail right through the various stages of the process. You can’t make a silk purse out of a sow’s ear is an old saying that can apply to making high feed value silage. Unless you are harvesting top quality grass at the right growth stage that has been appropriately managed since pre-closing you will not end up with top quality silage. Dry matter digestibility (DMD) is the key factor influencing silage feed value and this article gives practical tips on providing enough high DMD (target 75%) silage for your ewe flock next winter.

Aim to make 75% DMD silage for your ewe flock

How much silage do ewes require?

The guideline silage requirement for the average lowland ewe is 0.15 tons pit silage per ewe per month or 0.19 bales per ewe per month. Budget for 15 to 16 tons pit silage or 19 to 20 bales per 100 ewes per month. Where rotational grazing is practised, some or all of the sheep silage requirement will be met from removing heavy grass covers as high quality surplus bales. It is really important to clearly identify with permanent spray paint the different batches of bales. Ensure that bales likely to be high DMD material are stored so that they will be accessible when needed. The actual quality of the various batches should be determined later by analysing representative silage samples. Ideally ewes should be offered high feed value silage right throughout the housing period. Where the amount of high feed value silage is limited on a farm, target the best quality silage at the final 6 weeks pre-lambing – 30 bales or 24 tons pit silage per 100 ewes will be needed to cover this 6 week period.

Management at closing

Remove dead butt by grazing out properly to 4cm prior to closing for silage. Roll ground where necessary to reduce the risk of soil contamination. If clods of soil end up in silage (pit or bale) there is a risk that sheep fed on this silage can ingest the bacteria that causes listeriosis. Maintain soil pH and P & K indices at target levels based on soil analysis. When closing, apply up to 100 to 120kg/ha N in the form of an appropriate compound or protected urea allowing that about 30% of N previously applied for grazing will still be available to the plant. Don’t overdo it with chemical N as this can cause lodging of the crop pre-harvest which will negatively impact digestibility. Also don’t forget to replace P & K after silage crop with slurry and/or chemical fertilizer. A crop of grass silage will remove approx. 4kg P and 25kg K per ton of grass DM harvested.

Harvest at correct growth stage

The main factor affecting DMD is crop maturity at harvesting. A target cutting date for high quality first cut silage is between the 15th and 25th May before grass has headed out. Below average grass growth in recent weeks has forced some well stocked sheep farms to take an extra grazing from areas that would have normally been closed for first cut silage. Despite a later cutting date it is still possible to secure high DMD silage. Plan for cutting about six to seven weeks after fertiliser application (100kgs/ha N). A common reason for delaying harvesting is concern over whether the crop has used up all applied N. If in doubt contact your local Teagasc adviser to test grass sugar levels and nitrates – it may enable crop to be safely ensiled sooner given the right conditions. Don’t delay harvesting for a prolonged period as research has shown that for each week harvest is delayed digestibility goes down by 3% units per week (Keady et al, 2000). The aim is to harvest leafy material before grass heads out and before base of the sward begins to decay – regularly walk and inspect the crop, watch the weather and take the best available opportunity to mow around the planned harvest date.

Tips on mowing

The optimum time for mowing is in the afternoon of a sunny day when grass sugars have built up. In reality this is not always practical but at least aim for a dry day and allow the dew to evaporate from grass before mowing. Don’t mow too bare to avoid ensiling dead material and the risk of soil contamination. Ensure that mowers and tedding machines are set at the correct height to avoid rooting up soil. Where soil contamination may be an issue due to poor ground conditions at harvest, identify as silage not to be fed to ewes next winter.

Effect of wilting on silage quality

Wilting negatively impacts digestibility and the rate of reduction in DMD due to wilting has varied among different studies. Each day (24 hours) wilting will reduce silage DMD by between 0.5 and 2 percentage points. Therefore, aim for a rapid wilt of 24 to 36 hours after mowing. Target 25% dry matter at ensiling for pit silage and 30% dry matter for bales. Spreading heavier crops over the ground straight after mowing helps achieve this but is generally not necessary for light cuts. Surplus bales or light crops should be baled and wrapped relatively soon after cutting particularly if good drying conditions prevail.

Anaerobic conditions for good preservation

Ensure silage pit is covered and fully sealed as soon as possible after filling. With bales, extra layers of plastic wrap combined with careful handling and storage will help ensure air is totally excluded from the bale. Don’t allow birds or other vermin damage your silage clamp or bales and don’t forget to repair any bales damaged in transit to avoid moulds and wastage.

Let’s Talk Sheep Webinar

Check out the recording below of our recent webinar, where Dr. Tim Keady discusses in detail the key factors influencing silage quality and outlines the steps to follow to produce high feed value silage on your farm

Let's Talk Sheep is a series of webinars for Irish sheep farmers, hosted monthly by Teagasc. Find out more about the series here  

The Teagasc Sheep Specialists issue an article on a topic of interest to sheep farmers every second Tuesday here on Teagasc Daily. Find more on Teagasc Sheep here