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Catherine Hurley, B.Ag.Sc.
What is the country’s largest and most important harvest? Tillage farmers might disagree, but the answer is grass, the crop that is the staple diet for the majority of our beef cattle, dairy cows and sheep.
Although the mild spring saw some cuts of silage coming in unusually earlier, the coming weeks will see the silage season get into full swing, making it a good time to look at the nutritional aspects of silage and how to maximise the value of your crop.
Dry Matter Digestibility (DMD) is a term we’re all familiar with. It is the main factor that determines the energy (ME) concentration of silage and is also a key factor in its intake by animals. As DMD increases, so too does silage ME concentration and silage intake, which leads to improved animal performance. Fundamentally, this boils down to digestibility being the main factor influencing silage feed value for your stock.
The average digestibility of silage last year was 67.7%, but the DMD levels varied from as low as 50.8% to a high of 78.2% for Dairygold farmers who chose to test it.
Extra supplementation needs to be provided to compensate low DMD silage, adding additional costs to feeding. Levels of supplements depend on the feed value of the silage and the level of performance required by the group fed.
Increasing silage DMD increases silage intake and performance of lactating dairy cows. Teagasc studies regarding lactating dairy cows on a silage-based diet suggest the mean milk yield response was 1.65kg per cow per day for each 5% increase in DMD.
Studies carried by Teagasc Grange suggests it takes 17kg DM of 75% DMD silage to put on 1kg of carcass as opposed to 46kgs DM of 60% DMD to put on 1kg of carcass weight.
On average, each 5 unit increase in silage DMD increase;
Regardless of your take on farming, satisfactory animal performance is largely dependent on the adequate intake of good quality silage. Higher DMD silage lowers feeding costs while improving production and keeping more money for your back pocket.
How to improve silage digestibility – DMD
Harvest date is the key factor that affects silage DMD. Silage DMD declines by 3.3 units for every week delay in harvest data. Decide on when to harvest following an inspection of the sward canopy for presence of decaying lower leaves and seed heads.
If wilting silage, ensile within 36 hours and avoid soil contamination.
For each one-week delay in harvest additional concentrate must be offered to maintain animal performance as follows;
Closing up fields early enough is another crucial discipline for farmers looking to get an early cut of silage when grass digestibility is still at its peak.
To have enough bulk in the sward by a May cutting date, farmers need to think about closing up first-cut silage ground by the end of March.
Using additives can be beneficial on many levels. For example, some additives can improve preservation, others reduce effluent, or slow heating at feeding out. Higher intakes, reduced risks of mycotoxins and increased production levels are just some benefits associated with using additives.
To improve the crop, you must know what you’re working with, so a test to assess sugar levels is essential. The option of wilting will help to increase sugar content.