Estimated reading time: 7 minutes
Plaas Media’s twelfth Santam Agriculture National Silage Competition once again showcased impressive expertise among its participants. As co-coordinator, I was struck by the high level of skill demonstrated across the entries. Interestingly, the main challenge of the 2025 competition stood in stark contrast to the drought experienced in 2024; this time, excessive rainfall complicated the silage harvesting season for many producers.
While overall harvests were good, persistent rain from January through April made it difficult for producers in the summer rainfall regions to enter fields at the ideal cutting stage. Even so, the quality remained good and is an outcome that aligns with expectations when crops receive ample moisture.
Maize silage
The average dry matter (DM) content of this year’s maize silage entries reached an excellent 38,6%. This is slightly higher than previous years and nearly identical to that of the dry 2024, albeit for the opposite reason. In 2025, producers simply could not access muddy fields in time.
An interesting observation was the average protein content of 8,11% DM, which was higher than usual. This could suggest that plants were harvested at a younger stage, as younger maize plants typically contain higher protein levels than older plants. However, the average DM values did not reflect this.
Starch content averaged 34,04%, the highest in the competition’s history. Yet, this too contradicts the theory regarding younger plants. In addition to the higher protein levels, the DM and starch content underscore how effectively maize plants can accumulate valuable starch when allowed to mature beyond 35% DM.
Ash content
A concerning trend is the rising ash content of maize silage. Ideally, ash levels should be below 4% on a DM basis, yet the average recorded in 2025 was 4,86%. This increase can be partly attributed to the muddy field conditions producers had to work in, causing soil to cling to plant stems and be carried into the silage by tractor wheels during compaction. The top layer is especially affected, with ash content averaging 7,48% in bunkers and heaps.
The contribution of tractor wheels to soil contamination in silage is greater than most producers realise. Another contributing factor is when silage is loaded onto trucks next to the field using backhoes, and then transferred and unloaded at the bagging machine. This practice undermines the benefit of directly unloading freshly cut material into storage systems such as silage baggers or high-density balers. The highest ash content recorded in the competition was 35,48% from silage that was handled twice by backhoe.
Elevated ash levels disrupt the fermentation process, negatively affecting silage quality and intake. Excess ash also accelerates unnecessary wear and tear on machinery such as feed mixers.
Utilisation of silage
Total digestible nutrients (TDN) indicate the overall usability of a feed and represent the combined value of starch, fibre, protein, and their digestibility. The average TDN in 2025 was 71,77% – a 3% increase compared to 2024 – mainly due to higher starch levels and improved digestibility. Maize silage continues to rank among the crops with the highest TDN, reinforcing its value as a dependable and nutrient-rich feed source.
Fermentation properties
For maize silage, a pH of around 3,8 typically reflects successful preservation. In 2025, the average pH was spot-on. Aerobic stability – measured using the silage competition protocol’s standardised five-day aeration test – showed an average pH of 4,12 after five days of air exposure. This is a slight increase, which is desirable, but represents the average. The poorest-performing sample, on the other hand, reached a pH of 7,99 after five days, a level at which it can no longer be considered silage.
Lactic acid concentrations averaged 5,4%, while acetic acid levels were well balanced at 2,08% in bunkers and piles, and 1,38% in silobags and bales, indicating good preservation.
Sorghum silage
The inland regions experienced a particularly wet silage season until May/June, which hampered the harvesting of forage sorghum. Although rainfall during the growing season was favourable, the soggy soil conditions at harvest caused many tall sorghum plants to lodge. Sweet sorghums have a wider harvesting window of several weeks, because they are slower to dry off than maize.
Despite the challenging conditions, the sorghum silage produced had an average DM content of 34,4%, which is considered very good. Its overall quality also compares well to previous years’ averages.
Forage sorghums are generally easy to ensile, a fact that is reflected in the consistency of analytical results over the years. Both fermentation parameters and nutrient profiles remain in line with the norm.
Oat silage
Oat silage is South Africa’s second-largest silage crop and plays a key role in the winter rainfall regions. Based on the oat production cycle, the 2025 silage competition evaluated silages that were produced at the end of 2024.
The average DM content of the samples was an ideal 36,5%. One recurring concern, however, is that many producers chop their oat silage too coarsely. Although chop length is ultimately a decision made by the producer and nutritionist – and depends on several factors – excessively long particles can impede oxygen exclusion and increase wastage when the silage is fed to livestock. In 2025, the average chop length was 19,2mm, even longer than in 2024, signalling a move in the wrong direction.
Particle size was assessed using the Penn State particle separator. Ideally, about 60% of the sample should accumulate on the middle sieve. The competition samples averaged only 38,5%, indicating that the oats were generally under-processed.
Protein content
The average protein content of the oat silage was 9,31%, representing an improvement of nearly 1% compared to the previous year. This suggests that the oats were likely harvested closer to the optimal cutting stage (i.e., earlier), although there is considerable potential for improvement.
Protein is one of the most important nutrients, yet it is often lacking in a farm’s fodder flow. It is therefore surprising that more producers do not use oat silage as an opportunity to boost protein levels. Oats are often cut later in a bid to pursue higher yields, resulting in less protein in the crop. Protein levels of around 13% are achievable if the crop is harvested at the optimal stage.
Fermentation
Butyric acid remains a common challenge in oat silage fermentation, particularly in wetter silages that have not been wilted sufficiently. The problem is further compounded through contamination and slow ensiling. The highest recorded level in the 2025 data set was 1,81%, which can lead to intake issues. High butyric acid content significantly reduces silage palatability. While the 2025 average of 0,25% is less than ideal, it is consistent with what is seen globally.
The Santam Agriculture National Silage Competition provides more than just a ranking; participants receive a detailed report with actionable metrics and personalised comments. This allows producers to benchmark their silage against industry standards and seasonal data, highlighting areas where improvements can be made to improve silage quality and nutritional value. – Richardt Venter
For more information, contact Richardt Venter at richardt@agsci.co.za or 083 590 3014.
