Recent results show that average crude protein (CP) levels in 2016 silage crops are 14.1% and 14.2% for first and second cuts respectively. While this is similar to last year’s crop, Dr Dave Davies of Silage Solutions Ltd says producers should be aiming for around 16%.
“The increasing cost of fertiliser is likely to be a catalyst for low CP levels, which we’ve seen dropping over the last ten years. Sufficient nitrogen is essential to boost protein in the grass but producers have tended to cut back on its application and consequently, we’ve seen a knock on effect, with grass crops lower in protein than they could be.
“The problem is exacerbated by newer grass varieties, which are selected because they are higher yielding and therefore, require increased levels of nitrogen to sustain their crude protein concentrations. As well as this, the introduction of nitrogen vulnerable zones has undoubtedly led to more cautious application.”
Dr Helen Warren, European technical manager at Alltech, warns that silage-based rations this winter will require careful balancing, if the diet is to deliver optimum efficiency and performance.
“Forage-based rations offer significant potential. Not only are they usually home-grown and therefore more economical, their high fibre content promotes rumen health, improving overall diet efficiency.
“However, to get the most out of silage this year, it’s important that the diet is correctly balanced to deliver adequate rumen degradable protein (RDP), as well as rumen undegradable protein (RUP), and energy.”
A sufficient supply of RDP is particularly important, as it fuels the rumen microbes enabling optimum feed digestion. While this can be supplied from fat-coated urea, Dr Warren warns that this form of non-protein nitrogen (NPN) can be wasteful due to the sudden surge it supplies, and can even result in ammonia toxicity.
“A sustained-release NPN, such as Optigen, provides a much more consistent supply to the rumen microbes, avoiding the peaks and troughs seen with other sources. This enables the microbes to continue functioning, therefore optimising digestion, particularly of the fibre fraction of the diet. Additionally, Optigen allows a lower inclusion rate compared with other NPN sources, which creates space in the diet.”
When balancing the ration, it’s also important to take into account the dry matter of the silage she adds. “2016 silage analysis suggests dry matter is lower than last year, with second cuts slightly wetter than first cuts. Therefore, it’s important to remember that if the silage is wetter, the animal will get less protein per kilogram of fresh silage intake, which may further increase the need for supplementation.”
