Making quality silage with molasses

Teagasc research, states that grass silage accounts for up to 30% of the total annual feed consumed on both dairy and beef farms in Ireland. They also report, that silage production occurs on 85% of livestock farms, at a cost that exceeds €500 million annually. Farm Contractors Ireland (FCI) current price list, details, that the charge for bale, wrap, stack and move is €14.00 per bale plus VAT, with precision chop silage costing €115.00 plus VAT per acre. These figures, indicate that grass silage is therefore 2.0 to 2.5 times more expensive per tonne of dry matter (DM) than grazed grass.

The above facts don’t seem to resonate with farmers however, as the quality of grass silage has improved little since the 1980s. Teagasc figures show, that the national average dry matter digestibility (DMD) percentage value of silage has remained in the low to mid-60s within the intervening period. This quality silage, is of poor feeding value and will be of little benefit on farm. It will not repair body condition score (BCS) on dry dairy cows, increase weight gain on weanlings and most certainly, it will not finish cattle or put milk into the bulk tank. For these figures to improve, farmers will need to implement a structured approach to their silage making, with greater attention to detail given to the below steps,

1.       Cutting

2.       Wilting

3.       Treating

4.       Clamping

5.       Feeding out

Step 1 – Cutting

The two main influences on silage (DMD) value at feed out are sward conditions at closing and the grass growth stage at cutting. The positioning of the crops seed head at cutting has the largest impact on this. Once heading out has occurred, grass (DMD) value reduces by up to 0.5 units per day. A delay in cutting date from late May to early June can therefore reduce your main winter forage from a high quality to a maintenance feed. Weather conditions, in the immediate period prior to cutting can also greatly influence the overall quality of forage entering the clamp. Cutting in the afternoon, after a period of sunlight, will ensure that the maximum amount of sugar is drawn into the plant pre-cutting, therefore, leading to forage of a higher feed value. Grass, should not be cut too low however, as this can result in the lower quality dead butt of grass being clamped or baled. Moreover, it can also give rise to the possibility of soil contamination which can lead to increased levels of clostridia and listeria entering the clap, especially in periods of inclement weather.     

Step 2 – Wilting

Once cut, weather permitting grass should receive a quick wilting period of 24-48 hours. This, will aid in concentrating plant sugar levels, while also increasing crop (DM), therefore, leading to an overall better fermentation. However, it should be noted that over wilting can restrict fermentation due to an increase in grass (DM) and the absorption of sugars by both the plant and undesirable bacteria. Additionally, grass wilted to too high of a (DM) content will be more difficult to ensile and can lead to the increased possibility of air penetration in the clamp. Ideally crops should be wilted to a (DM) content of 28-32% to allow for best preservation to occur.

Step 3 – Treating    

Targeting a crop sugar content of 3% or greater pre-harvest should be a prerequisite. Reaching this sugar content is not always possible however and can be influenced by many different factors. Sward type, state of lodging and inclement weather can all effect a standing crops sugar content. Where plant sugars are below 3%, adding a sugar-based additive in the form of molasses as a fermentation stimulant can be very effective. Depending on sugar levels, application rates can vary from 9 to 18 litres per tonne of fresh herbage. These rates, will allow for increased preservation acid production, reductions in ammonia N and silage pH while also aiding in the fermentation.

Molasses application rates:

Molasses Application Rates (Grass Preservation)

Grass Sugars                                                        Molasses Application   


                                               Kg/tonne                        Litre/tonne                         Gallon/tonne

 0-1%                                           26                                       18                                             4

 1-2%                                           19                                       14                                             3

 2-3%                                           13                                        9                                              2

Typical Requirement at 9 Litres/Tonne Silage

                                                  10t/ac                                 12t/ac                                     15t/ac

 20 acres                                   1800L                                  2160L                                      2700L

 60 acres                                   5400L                                  6480L                                      8100L


Step 4 – Clamping

Prior to clamping, empty silage pits should be inspected, cleaned and any cracks in concrete repaired. Clamping, once commenced, should occur promptly, therefore allowing for anaerobic fermentation to occur immediately. Clamps, should be filled in layers, with consolidation occurring every 15cm if possible, this will be dependent on trailer throughput however. Molasses, where used, should also be applied in layers, therefore, allowing for an even application, a better consolidated clamp and an overall better fermentation. Clamps should be filled in a wedge like shape to the front. Achieving a speedy seal on both silage clamps and bales is key to minimising forage waste. Where possible, clamps should be filled in one day. For best practice, bales should also be wrapped the day of making with this occurring ideally at final point of storage.    

Step 5 – Feeding Out

While feeding out might be a distant thought for most farmers, good housekeeping practices during this period can prevent large forage quality losses. Cleanliness in the immediate area around the face of the clamp is vital in this respect. Mouldy silage deposits, can lead to the contamination of the exposed clamp face through mould spores, thus, leading to an increased rate of aerobic spoilage. Avoiding a build-up of this material is therefore extremely important. Maintaining a clean tight clamp face is also good practice. Farmers, should aim to move across the clamp face quickly, through the use of a well-maintained shear-grab, therefore, preventing additional aerobic spoilage. Preserving the air seal on the clamp via use of regular movements of the cover should also be adhered to. Finally, it is important to avoid pulling the cover down over the clamp face during feed out. This will prevent the creation of a microclimate, thus, reducing the growth of yeasts and moulds which increase the risk of spoilage and heating.