Aug 25, 2021
Applying bacterial forage inoculant uniformly to baled silages
Aug 25, 2021
The use of quality, strain-specific bacterial forage inoculants help to produce more nutritious and palatable feed, reduce wastage and ultimately, increase the efficiency of milk and beef production.
Correct application technique is essential to ensure these benefits are achieved. Any variation in the distribution of the inoculant will impact upon fermentation, leading to complications in silage stability, feeding out and livestock performance.
Bacteria don’t walk, run or swim! For any bacterial forage inoculant to work, it must come into contact with the forage it is treating. Whilst effluent produced by fermentation in high moisture forage allows some movement of bacteria through the matrix, on the whole, bacteria remain largely where they were applied.
A clear analogy can be drawn to sunscreen. You can put a few drops between your toes and hope that it protects the rest of your body, or you can cover all of your exposed skin using the correct volume!
Forage inoculants can be applied at a range of rates from 10 mL/t up to 2 L/t. If a standard droplet has a volume of 50 µL, then an ultra-low application rate of 10 mL/t equates to 200 droplets. At the other end of the scale, a standard application rate of 2 L/t will produce 40,000 droplets.
Modern forage harvesters have ‘accelerators’ that propel cut forage from the chopping unit, up the chute and into the following truck or trailer. These accelerators produce astonishing air speeds of up to 68 metres per second or almost 245 km/h!
The ‘venturi effect’ produced by this rapid airspeed smashes the droplets to one-tenth of their normal size, meaning 2000 droplets are produced from the same ultra-low application rate of 10 mL. This mist is then homogeneously mixed with forage particles as they move up the chute and are expelled from the forager into the trailer.
International research has repeatedly demonstrated that ultra-low volume application is as effective in distributing forage inoculants across a range of forage types and different dry matter content as standard application rates (Kung, Marley and Pahlow).
Balers and forage wagons do not have accelerators. This means the droplet size of the applied inoculant will remain unchanged (50 µL) and the droplets will not be homogeneously mixed with forage particles. This means the distribution of bacteria contained in the inoculant and their beneficial effects upon fermentation will be limited to where each droplet lands.
Field research compared the distribution of bacterial inoculant when applied using ultra-low application rates with either a self-propelled forager or a forage wagon (Marley). The applicator on each machine was calibrated to apply one million bacteria per gram of forage. Forage samples were collected and assessed.
The variation in bacterial distribution in forage cut by harvesters equipped with an accelerator was extremely small, ranging from 83% to 122%. By comparison, the variation of bacterial distribution in forage wagons and balers was huge, ranging from 0.16% to 1160%!
The second problem with applying inoculant via forage wagons and balers is that the number of droplets of bacteria is entirely dependent on the application rate of the additive. For this reason, standard application rates of 1–2 L/t are recommended. Put simply, higher application rates will produce more droplets – and hopefully, more consistent distribution across the bale and ultimately, silage quality.
Other research has confirmed that positioning the application nozzle at the front of the press chamber (III on drawing below), as opposed to before the pick-up front or over the pick-up, is most effective at reducing inoculant loss or drift. (Dulcet and Borowski).
The application method of forage inoculant must be appropriate to the harvest equipment used. Ultra-low volume application is only suitable for use on harvesters equipped with a forage accelerator. Standard rate application should be used on balers and forage wagons that are not equipped with accelerators. The position of the applicator is also important in achieving best results.
|Forage wagon||Self-propelled forager harvester|
|% bacteria per gram of grass||Untreated||Low volume||Untreated||Low volume|
|% Variance||+/- 721%||+/- 1160%||+/- 18%||+/- 22%|