As farmers start turning spring surpluses into supplementary feed, Beef + Lamb New Zealand’s “Making every tonne count” webinar has some excellent advice on how to maximise the quality silage and balea
The webinar, which was organised by Beef + lamb New Zealand’s Central Otago Farming for Profit committee, features Dr Jakob Kleinmans, a forage and nutrition consultant from NutriAssist Ltd.
He talks about harvest timing, compaction, sealing and fermentation as being the most critical factors in making quality silage or baleage.
He said harvest timing was a trade-off between yield and quality. As the yield goes up, so does the quantity of Neutral Detergent Fibre (NDF), which means the plants start to become woody. The higher the NDF, the lower the intake and the lower the crude protein. Growing and lactating animals in particular need high levels of protein so to maximise protein levels, grass silage should be cut while the pasture is still leafy.
Conditions are ideal for fermentation at 30-40 percent drymatter, below 28 precent, fermentation will be poor and the silage stack will produce effluent.
Above 40 percent, the silage will be too dry. Compaction will be poor and the stack will generate heat and mould.
To estimate drymatter, Dr Kleinmans recommends taking a handful of chopped or well-mixed plant material, squeezing into a tight ball for five to ten seconds and observing what happens.
If the ball forms easily and juice is released, the drymatter will be below 25 percent and too wet for harvesting.
If the ball forms but breaks apart easily without any juice, then drymatter will be between 30-40 percent and ideal for harvest.
If the material barley sticks together and feels dry and springy, drymatter will be above 40 percent and too dry for compaction.
Fermentation
The three factors that control fermentation are air (lack of), sugar and drymatter.
If a silage stack is airtight it can last for many years. Once air enters, the yeast becomes active, the temperature rises, mould develops, energy is lost and intake drops.
Compaction is the cheapest insurance in a silage stack. Dr Kleinmans suggests building the stack with thin layers of less than 15cm, using heavy tractors or loaders to continually compact the stack to a target density of 230kgDM/metre 3, and sealing immediately.
He acknowledges that it isn’t easy to measure compaction, but as a rough guide, when standing in front of the stack, if a person can get their fingers into the stack, it is too loose. Ideally, they should only be able to get their fingertips into the front of the stack.
Spoilage and feeding out
Spoilage is caused by oxygen penetrating the front layers of the silage causing CO2 to flow out the bottom of the stack.
Ideally, the feeding out rate should be greater than the rate of air penetration.
Baleage
Grass bales should contain 180-220kg DM/m2.
Dr Kleinmans recommends contractors use maximum pressure in the baler chamber and wrap the bales with stretch film within two hours – certainly no more than six hours.
For fermentation to occur, there needs to be sufficient sugar in the crop. Ryegrass is naturally high in sugar, lucerne and clover plants are not. These legumes need to be wilted sufficiently to allow sugar levels to rise before being made into silage or baleage.
Clostridia
Clostridial spores are the villains of silage fermentation. The spores occur naturally in soil and they like wet conditions. They can become incorporated into the silage when the mower bar has been set too low, when raking wet crops, when the stack is built on muddy soils and when the silage stack is flooded.
Silage should have a pH of 4.5, which indicates a healthy level of lactic acid. When clostridia spores infiltrate the silage, the pH goes up and the silage will smell like vomit.
Mould
Visible mould is never acceptable in silage. Mycotoxins may still be present, particularly if infection occurred before the crop was harvested. Mould almost always indicates oxygen ingress resulting from poor sealing, damaged bale wrap, inadequate density or a slow feeding out rate.
It is important to remove and discard all visible mould.
Silage analysis
Dr Kleinmans describes a silage analysis as a management tool- not just a lab report.
Measuring ME, crude protein, NDF, pH, Ammonia and Butyric acid it will indicate animal performance (ME), protein supply, intake potential (NDF), fermentation success (pH), protein breakdown (ammonia) and clostridia risk (butyric acid).
The results will indicate what class of livestock the silage is suitable for.
Watch the webinar here - Making every tonne count.