For producers looking to drive milk production from forage, having high quality, palatable silage stocks is key.
Widespread research suggests the multi-cut approach of taking more cuts per season from younger grass can offer a number of potential benefits, but this can only be achieved if conditions at ensiling are right.
The fermentation process in particular is critical to making sure the crop is the highest quality it can be, according to Volac silage scientists Mark Leggett and Philip Jones who recently conducted a multi-cut study in South Wales.
Samples from four cuts were tested between May and August 2018, taken from a specified testing area in the same field each time.
Mark Leggett: “The quality of the crop you are getting from a multi-cut system is more uniform and this was evident in in the quality of grass we looked at during the trial.
“The crop consistently had high digestibility and energy levels for milk production as well as higher protein levels because of the younger stage at which the grass is cut.
“Grass in a multi-cut system can produce a good quality starting material for feeding, but you need to make sure it maintains this nutritional benefit once it has been ensiled.”
Mark Leggett: “Because of the shorter window between cutting, there is a risk of elevated nitrogen levels in a multi-cut crop which can slow down the decline in pH during ensiling.
“Potentially higher protein levels found in younger grass can also slow down or resist the pH change taking place, a process that ideally needs to happen as quickly as possible as a low pH is key to controlling the activity of bad bacteria.
“Slurry applied to the crop also has less time to wash off the leaf, which creates a risk of contaminating the fermentation with bad bacteria."
Philip Jones: “We found this during the trial, with slurry bacteria counts on untreated samples found to increase throughout the season.
“The combination of large numbers of slurry bacteria with a potentially slow decline in pH creates a ‘perfect storm’ leaving the forage vulnerable to high DM losses."
Mark Leggett: “Despite the exceptionally dry conditions of last summer which meant cut three, taken on July 3 2018, was ensiled at 50 per cent dry matter, we were able to achieve higher lactic acid bacteria counts when we treated with an additive compared to levels which were naturally present in the untreated samples.
“Consequently, pH levels in the treated samples declined rapidly, within the first one to three days after ensiling, whereas untreated samples struggled to decline, even after one week and beyond. It did not reach the same levels as the treated silage, even after three months.
“This slow fermentation therefore gave slurry bacteria the opportunity to multiply in the untreated silage ultimately resulting in high dry matter losses, whereas the fast fermentation seen in the treated silage prevented this from happening.”
Philip Jones: “We also saw clostridial activity in untreated samples, creating butyric acid, a foul smelling by-product which can reduce silage palatability. In the treated samples there was no butyric acid present, as the clostridia were suppressed by the low pH.”
Mark Leggett: “Challenging fermentation conditions were visible on samples from all of the cuts taken, which would create the potential for dry matter losses in the clamp and the risk of a lot of butyric silage in a real life situation if silage was left untreated."
Philip Jones: “Applying an additive means control over the fermentation process, as well as consistency every time rather than relying on what the natural populations of bacteria are at any given time which is likely to range hugely due to external factors.
“For those chasing yield and quality, it is surely desirable to have this level of control.”