Lactic Acid: The Gold Standard of Silage Fermentation

Why This Powerful Acid is Key to Better Silage on Irish Farms

When it comes to making top-quality silage in Ireland, there’s one compound that every farmer should know about — lactic acid. It’s the gold standard of silage fermentation, and understanding how it works can mean the difference between high-quality forage and costly waste.

In this post, based on the Precision Microbes Silage Sessions with Ryan Duffy, we break down the science in simple terms so you can make better silage and boost your farm’s performance.

What is Lactic Acid, and Why Does it Matter?

Lactic acid is a natural preservative produced during silage fermentation. It’s made by lactic acid bacteria (LAB) — beneficial microbes that feed on sugars in your grass and convert them into acids that preserve the forage.

Here’s why lactic acid stands out:

• It’s strong and highly effective at reducing pH.
• It preserves nutrients (such as crude protein and metabolisable energy).
• It gives silage its characteristic sweet, acidic smell when fermentation goes well.
• It helps protect against bad bugs that cause bacterial spoilage.

When silage contains a high amount of lactic acid, it stays fresh and palatable, retaining a full complement of energy — especially important for high-performing animals like dairy cows or finishing cattle.

Grass Sugars: The Fuel for Fermentation

Lactic acid bacteria need fuel — and that fuel comes in the form of plant sugars, mainly glucose and fructose.

These are the fermentable sugars (known as water-soluble carbohydrates) in grass, and they play a key role in determining:

• How quickly the silage ferments
• How low the pH can drop
• How many nutrients and how much dry matter is retained

💡 Top Tip: Grass harvested in the late afternoon often has higher sugar content due to daytime photosynthesis — ideal for fermentation.

Homo-Fermentative vs. Hetero-Fermentative LAB

Not all lactic acid bacteria are created equal. There are two main types:

Homo-Fermentative LAB – The Gold Standard

• Fast acting and efficient
• Convert plant sugars into lactic acid only
• Drop the pH quickly
• Preserve up to 99% of the energy from the original crop sugars
• Greatly reduce the risk of bacterial spoilage

Hetero-Fermentative LAB – Less Efficient

• Slower acting
• Convert sugars into lactic acid plus other byproducts
• Result in a slower pH drop
• Allow further time for bad microbes to act
• Lead to nutrient loss

In fact, homofermentative LAB are:

• Twice as efficient at converting glucose to lactic acid
• Six times as efficient at converting fructose to lactic acid

Clearly, homo-fermentative bacteria are the microbes we want dominating in our clamp or bale.

Precision Microbes Silage Additive is a liquid, ready-to-use (RTU) formulation containing live bacterial agents, specifically lactic acid forming bacteria (LAB) and homofermentative bacterial populations. Designed for efficient crop preservation, it promotes a rapid pH drop in both clamps and bales, ensuring high-quality silage. The product is organic certified and can be applied using either ultra-low dosing or standard dosing methods, offering flexibility and ease of use for farmers aiming to enhance silage fermentation and nutrient retention.

Why a Fast Drop in pH is Crucial

The main job of lactic acid is to reduce the pH of the silage as quickly as possible. A fast pH drop:

• Stops harmful microbes like clostridial and enterobacterial species from proliferating
• Preserves more of the crop’s valuable crude protein
• Retains more energy and dry matter from the original crop
• Results in a golden and sweet-smelling silage

If pH drops slowly:

• The likelihood of nutrients being lost are heightened
• Dry matter is broken down
• Unwanted fermentation (e.g., butyric acid and biogenic amine formation) can occur

Lactic acid is far more powerful in reducing pH than the other acids we encounter in silage clamps and bales and therefore promoting the production of this is a fundamental aspect to making consistently great silage.

The Benefits of a Lactic Acid-Dominant Fermentation

✅ Higher Feed Quality
With more metabolisable energy and crude protein preserved, silage supports better milk yield or liveweight gain.

✅ Improved Palatability
Animals are more likely to eat well-preserved, sweet-smelling silage.

✅ Less Waste, More Efficiency
Lower nutrient and dry matter losses mean more value from each acre of grass.

✅ Supports Rumen Health
Hygienic silage supports better microbial balance in the animal’s digestive system.

How to Maximise Lactic Acid Production

If lactic acid is the goal, you need to provide the right conditions for homofermentative LAB to thrive. Here’s how:

1. Harvest at the Right Time

• Aim for a crop with high sugar levels
• Late afternoon cutting can help boost sugar content

2. Wilt to the Right Dry Matter

• Target 28–32% DM
• Avoid overly wet or dry crops

3. Compact and Seal Well

• Exclude oxygen as quickly as possible
• Oxygen delays fermentation and encourages spoilage organisms

4. Use a Proven Lactic Acid Bacterial Additive

• Products like Precision Microbes Silage Additive supply large populations of homo-fermentative LAB
• This ensures rapid fermentation, better pH drop, and nutrient retention

As Ryan Duffy puts it:

“It’s not just about fermenting — it’s about fermenting right.”

Why This Matters for Irish Farmers

In Ireland, we often face short periods of good weather, variable grass quality, and unpredictable harvest conditions. A strong fermentation helps protect the investment you’ve made in your forage and ensures you’re feeding your stock the best possible quality.

Whether you’re producing silage for:

• Dairy cows
• Finishing cattle
• Sheep or sucklers

…getting lactic acid working for you can improve your feed value, animal performance, and farm profitability.

Final Word: Make Lactic Acid Your Silage Ally

Lactic acid isn’t just a byproduct — it’s your best tool for preserving silage quality.

If you want:

• Faster pH drop
• Better nutrient retention
• Less spoilage
• Happier, healthier livestock

Then promoting lactic acid fermentation with high-sugar crops, good silage practices, and the right additive is a must.