Silage lessons from a wet year
Good quality silage can still be made in a wet season provided the sward and the cut grass are properly managed, believes nutritionist Mateusz Mieczkowski.
“With feed costs soaring it’s important to try and make the best possible silage by using an appropriate silage additive, says Mr Mieczkowski of Envirosystems.
“Additive will help speed up and improve the fermentation process and increase its nutrient value. Halting the development of spoilage organisms and lowering the pH as quickly as possible is essential,” says Mr Mieczkowski, who believes there’s confusion among dairy farmers about how silage additives actually need to work.
“The nutritional quality of young, wet silage doesn’t necessarily benefit from additives containing lactobacillus bacteria and enzymes,” he says.
“Additives based on lactobacillus bacteria produce more lactic acid in the crop and use up sugar. The bacteria soften the cell wall of the ensiled grass causing nutrient loss, effluent problems and reduced intakes.”
Does lactic acid play a key role in silage production?
A lot of last year’s silage was wet and acidic. Intakes have been low and many types of silage have been producing three litres less milk compared with a normal year. Mr Mieczkowski says it’s important to consider if the addition of lactic acid bacteria is the correct way to make good quality silage.
“Wet and acidic silage is no use to dairy cows. While many believe that lactic acid is the most important factor influencing silage quality, that isn’t actually true in all cases.
“It’s vital to know the amount of lactic acid that’s in the silage – and that should be between 6-8% of dry matter (DM). Lactic acid is the strongest acid found in silage – apart from propionic acid that occurs in 1% of the DM.”
“When there is more than 8% lactic acid in the DM the silage will be acidic and less palatable to cows. Intakes are reduced and yields affected. One gram of lactic acid is produced from 1.8g of sugar, but very wet silages have 12-15 % of lactic acid so up to 126g of sugar is lost. It takes extra energy from the silage by transforming sugar to lactic acid.”
The purpose of using a silage additive is to preserve the nutrients, (sugars and proteins) while retaining stability and dry matter. Achieving this without converting too much plant sugar into lactic acid means higher intakes.
“To retain maximum nutrients in wet conditions, rolling the clamp carefully in layers with a tractor with narrow tyres and being careful not to damage the structure of soft young grass means less effluent loss and good compaction when feeding out,” says Mr Mieczkowski.
Field work
However, he stresses the quality of silage at feed-out has as much to do with how the grass is managed and harvested as it does with how the grass is treated as it goes into the clamp.
He believes the correct timing of rolling and harrowing before grass really starts to grow has a direct impact on the physical structure of the plants affecting grass yield an acre and on the way the crop copes with the ensiling process.
“Harrowing at the right time produces cleaner fields, enables grass to start growing earlier, improves fertiliser uptake and limits soil contamination of silage going into the clamp. Rolling too is important; it helps root development and encourages beneficial micro-flora in the soil to thrive.
“Harrowing removes unwanted ‘pollutants’ from the sward such as debris and dead grass. When these materials get into the clamp they’re introducing spoilage organisms – and that’s something to be avoided at all costs. Highly productive grass varieties won’t perform or ensile to their full potential if they’ve got to cope with the effects of debris in the sward and spoilage organisms during the ensiling process.”
Fertiliser
As well as nitrogen levels, it’s important to consider how much potassium is needed. Potassium helps the assimilation of nutrients from the soil and improves plant health.
“If you’ve got healthy plants with more nutrients present, the silage will be stronger, healthier and able to produce more milk.”
“Phosphorus levels are critical too and improve grass quality, making plants more elastic, greener and stronger. These plants contain more nutrients and are easier to ensile.”
Weather
“The best silage is made in the best weather, so focus on weather conditions and not just on trying to get the biggest crop,” says Mr Mieczkowski.
“Don’t wait for optimal growth to achieve optimal nutrients. Young grass made into silage has less fibre to produce a rumen mat, but is rich in nutrients.”
Mr Mieczkowski says silage cut in early May contains fewer spoilage organisms to avoid secondary fermentation. Later cuts contain higher levels of mycotoxins. When grass plants are dry there are higher concentrations of active spoilage organisms such as moulds and yeasts, which become more active and stronger after ensiling.
“Very mature grass contains more mycotoxins – both before and after ensiling. After heavy rain, a lot of soil will be splashed on to grass plants creating soil contamination with butyric bacteria developing on plants before harvesting. Always cut wet grass at slightly higher levels – say 6cm – to avoid soil contamination.”
Case study – John Morley, Appleby, Cumbria
Like many dairy farmers last year, John Morley had to cope with difficult silage-making conditions on his farm in Cumbria.
Persistently bad weather delayed third cut until 10 October, and he admits he didn’t have high expectations of its feed value.
“I wasn’t expecting much from this third cut because it was so late in the season. But the analysis showed we’d turned a potential disaster into a good quality forage with a 76.5 D-value, 19.7DM and 12.2 ME. It turned out to be better silage than the second cut.
“The conditions underfoot when we made this silage were terrible; tractors were spinning and throwing a lot of soil up so we feared the worst,” says Mr Morley, who milks 230 9,500-litre pedigree Holsteins at Appleby with his son John.
This third cut silage was treated with an inoculant based on bacillus bacteria, not lactobacillus, with the intention of retaining more energy in the forage in the form of sugars.
Secondary fermentation was the big risk with this crop, explains Liz Russell of Envirosystems. “However, we managed to preserve the nutrient value and reduce the activity of spoilage organisms, which are the major problem when making silage in wet conditions.
“Inoculating the silage with the right bacteria to produce a silage of high-feed value, but one that has retained its stability in the clamp was what we aimed for and we achieved that.
“Limiting the activity of spores and moulds that are more prevalent in wet conditions must be a priority if farmers want to produce good quality silage in changing climatic conditions.
“Also, cut grass when it’s at its optimum feed value and don’t be dictated to by the weather.”
This winter’s TMR mix includes grass silage, pressed beet pulp, straw and 5kg of blend a head.
“We’ve got to be ready in future to cope with the sort of weather we had last year. The bacillus bacteria prevented spoilage losses that we thought would be inevitable,” says Mr Morley.
Farm facts
- 230 Holstein cows
- 9,500-litre herd average
- Forage acres 80ha 1st cut, 80ha 2nd cut and 45ha 3rd cut.
- TMR ration grass silage, beet pulp, straw and blend
- Out of parlour feeders