Every so often a producer or his nutritionist has to analyse his silage. Part of the Santam Agriculture National Silage Competition, hosted by Stockfarm/Veeplaas, entails a comprehensive nutritional value analysis of the silage entered in the competition. In addition, some extra parameters are measured to better describe the quality of the silage.

So what can we do with all these figures? It is in fact a valuable tool to measure your silage and to improve going forward, provided that you correctly interpret the silage analyses.

Depending on the analyses that has been done, there are nutritional aspects such as basic dry matter (DM), protein, starch and fibre that can be analysed. A more complex analysis report also refers to the level of minerals, fibre fractions, starch, protein degradation rates, and even the fermentation profile.

Important parameters

Yet the most important information of any analyses remains relative and depends on the application of the feed, the nutritionist’s approach, the prevailing market price of maize and protein sources, as well as the amount available. Hence there is no short answer as to which silage is best.

The formulas used in the National Silage Competition take into consideration more than 25 different parameters in six evaluation groups – with all values carrying a relative weight – to eventually award a point out of 100 to the particular silage.

A number of conclusions can be drawn from a few important parameters and a quick comparison can be made between two silage samples. For example, starch in maize silage is one of the first figures everyone looks at when they receive their analysis back from the laboratory. They tend to be happy with the higher starch content, because maize silage’s role and contribution is after all related to starch.

Digestibility and usability

Yet one should always keep in mind that higher starch levels are accompanied by drier silage which was cut later, when the plants were more mature. This mostly means that the fibre, especially the poorly digestible components, is also higher. In other words, it is the overall picture of digestibility and subsequent utilisation that really counts.

When cutting early, the starch is definitely lower as starch formation has not yet been completed. However, the protein content is slightly higher, because the plant was younger at the time of cutting.

A thorough nutritional analyses can therefore give someone who was not present when the silage was made and did not see the silage, a very good indication of what happened when it was cut.

Management of silage

During the competition, the judges consider several parameters that are not regularly evaluated on farms. The judges for example look at compaction, aerobic stability after five days, and loss of organic matter from the top layer of the bunker. These figures give a good indication of management during the silage-making process.

There is a correlation between how well the compaction was performed and how dry the silage was. The data undoubtedly shows that, with enough effort, a dry silage can be compacted just as efficiently as a wetter one – measured in kilograms dry matter per cubic metre.

Weaker compaction, and often unstable silage after the five-day aerobic test, tend to correlate with the fermentation profile, measured by the pH (acidity), volatile fatty acids and lactic acid. Silage analyses can be taken a step further by looking at microbiological populations of e.g. yeasts and fungi. Silage fermentation is a bacterial, anaerobic process. Spoilage organisms, on the other hand, are mainly aerobic or at least dependent on a higher pH.

Hence, it is clear that silage analyses should be done regularly and should preferably be evaluated by a registered animal nutritionist. In this way, we can take some lessons from what was optimal or sub-optimal, and this will be to the advantage of the farmer and the improvement of silage over the long term. – Richardt Venter