Ensiling Multi-Species Swards
Dr Dave Davies Independent Silage Researcher Silage Solutions Ltd

We keep hearing in the farming press about multi-cut and now multi-species swards. Well, these two things are completely different! However, to be successful with multi-species swards a multi-cut approach is the way to go!!

Multi-species swards contain a mixture of species of grasses (including, for example: Ryegrass, Timothy, Fescues, Festulolium and Cocksfoot), legumes (including, for example, Red, White and Alsike Clover, Trefoils, Lucerne and Sainfoin) and broad-leaved herbs (including, for example, Chicory, Plantain, Yarrow, Sheep’s Burnet and Sheep’s Parsley). Whilst this looks complicated in terms of silage-making a few key facts need to be borne in mind.

Firstly, to maintain both good sward consistency and silage nutritive value, these swards need cutting every 4.5 to 5.5 weeks. Some of the broad-leaved herbs will develop seed stalks and seed heads within a matter of days, this not only reduces the silage quality by increasing the undigestible NDF content but also reduces these components of the sward to recover after harvest.

Therefore, maintaining a close eye on the swards to cut at the right time is essential. By doing this you will improve subsequent silage or grazing sward quality. Hence the earlier comment of treating multi-species swards as a multi-cut silage system. Cutting height should be ideally 10cm but not less than 7.5cm. This is to ensure that the crowns of broad-leaved herbs, such as chicory, and some of the legumes are not damaged as this is their growing point.

Multi-species swards tend to have a lower dry matter and can wilt slowly. This is due to the non-grass components of the mixture, for example some of the broad-leaved herbs, such as chicory, wilt very slowly – under some weather conditions wilting for 48 hours may only increase the % DM content by 3-4%. Therefore, if you are planning on using the multi-species sward as a regular silage crop, leaving out chicory from your mix would benefit the dry matter content of the silage you produce.

Ensiling-Multi-Species -swards-facts

In terms of the silage preservation process a few facts need to be kept in mind. Multi-species swards are higher in protein and mineral content, and citric acid cycle components, but lower in sugar (Water Soluble Carbohydrates). Alongside this, as already stated, they are slower to wilt and often result in lower % DM at ensiling. The higher levels of protein and minerals, whilst excellent for silage nutritive value, result in a higher natural buffering of the pH decline in the clamp, this is further exacerbated by the citric acid cycle acids. Alongside this, the lower sugar content means that there is less substrate (food) for the good silage bacteria to produce the lactic acid to preserve the crop. 

Finally, to achieve the magical stable pH in the clamp, the generally lower % DM content means more acid is required than for a dryer crop. However, because of some of these factors and the way they are fermented during the silage fermentation phase, end-products that are inhibitory to the growth of yeasts and molds are produced, leading to improved aerobic stability at feed-out.

Thus, summing up, these attributes mean that the greatest risk is to the silage fermentation process and controlling this should be the main focus and aerobic spoilage at feed-out will be a much lower risk and should be more than manageable by good clamp and ensiling management.

Therefore, to control the fermentation process an inoculant containing 1,000,000 homofermentative lactic acid bacterial application per gram of fresh forage is essential. The main homofermentative bacteria are L. plantarum, Pediococcus pentocaseus and P. acidilactici. The heterofermentative inoculant bacteria, the main ones being L. hilgardii, L. buchneri, L. kefira, L fermentum and L brevis, will have a detrimental effect on this preservation process whether applied alone or in a mixture with the beneficial homofermentative species and so products containing this species should be banished to the bin for any multi-species sward. Alternatively, a chemical additive can be used and these should contain the food grade preservatives sodium nitrite and potassium sorbate.

Using these additive types, alongside good ensiling management, will help to ensure a good preservation process occurs, which will preserve more of the forage nutrients through into the silage and also give the silage a sweet smell enhancing palatability and intake.

One last note, on feed-out ensure an analysis of at least the protein and preferably the NDF as well is conducted by traditional chemical methods not NIRS prediction as the current NIRS prediction models will analyse your silage incorrectly, probably underestimating the protein content and over-estimating the NDF. Thus, making your multispecies sward silage appear, on paper, as lower quality than you hoped. The animals will tell you the truth! In addition, make sure you do a mineral analysis to benefit from the higher mineral content from this silage type.

Good luck!

multi-species-sward-Scotland
Multi-species sward in south west Scotland courtesy of Stephen Caldwell - Grass Science Seeds.

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