Conversations: Ask your nutritionist about silage quality and hygiene

Having to throw away spoiled silage can be tough: The losses involved are right there to be seen, almost like dollar bills being pitched. Feeding spoiled silage can have more serious consequences, including decreased intakes, reproduction problems and reduced production, leading to bigger losses. As producers and their advisors meet in the conference room (or across the kitchen table), silage quality and hygiene should be subjects of conversation.

By Renato Schmidt, Ph.D. and Bob Charley, Ph.D.

Making top quality silages means starting with high-quality forage crops in the field. The ensiling process then relies on efficient conversion of sugars to acids – mainly lactic acid – under anaerobic conditions, to produce a stable, acidic material. Acids are produced by lactic acid bacteria either naturally coming from the field or added as microbial inoculants, to ensure a dominant population of efficient, effective bacteria. There are a number of microbes that can otherwise dominate, potentially causing significant spoilage.

Bob Charley

Below are a few questions to help focus on and understand potential issues, specifically with clostridia and yeasts in silages.


1) What issues can clostridia cause in silages?

Clostridia are in soils and manure, and can contaminate crops in the field. In silage, they grow anaerobically and can ferment sugars and lactic acid to butyric acid and degrade proteins to produce biogenic amines and ammonia. The end result of a clostridial silage fermentation is a foul-smelling silage that is difficult to feed and can cause health and reproductive issues. In addition, some clostridia can carry through into the milk and even cause problems in cheese making.

Ask your nutritionist about how to avoid getting silages spoiled by clostridial growth to help minimize production, health and reproduction issues in your herd.


Renato Schmidt



2) If clostridia are anaerobic, why do they sometimes occur in aerobically unstable silages?

Air penetrates the silage mass during feedout and is utilized by aerobic bugs, e.g. yeasts, that can grow on sugars and lactic acid in silage. The consumption of oxygen in these niche spots can subsequently restore anaerobic conditions that, along with increased pH due to lactic acid consumption by the yeasts, allows clostridia to become active and grow.

Discuss how to prevent aerobic growth of yeasts during feedout, and how to manage your silages to minimize aerobic spoilage.


3) What causes aerobic spoilage?

Yeasts that grow on sugars and/ or lactic acid are the initiators of virtually all heating (aerobic spoilage) events in silages. In the presence of air (oxygen), yeasts grow, generating heat, causing significant energy losses and consuming lactic acid, raising silage pH. This allows opportunistic microbes (bacilli, molds, listeria, clostridia) to become active and grow, consuming nutrients, generating more heat and potentially producing toxins. Preventing yeast growth is key to minimizing spoilage, maximizing the quality, and quantity, of silages available to feed.

Review your records to see if you have a history of heating events, especially in crops prone to aerobic spoilage (eg. corn, HMC).

4) What can be done to inhibit or reduce the growth of yeasts?

Make sure the crop is ensiled at the recommended stage of maturity, DM content and chop length. Utilize an approved inoculant to improve aerobic stability. Pack all silages and HMC crops tight to squeeze out trapped air, cover and seal as soon as each silo is filled. During storage, monitor condition of the cover and patch holes as necessary as soon as possible.

Review good silage management practices and set realistically achievable goals for key parameters (DM, chop length, packing density, etc.).


5) What can you do if you can’t afford to dispose of silage that did not ferment well?

Feeding spoiled silage needs to be managed very carefully. Moldy or obviously spoiled patches should be pitched out. If the whole silage mass did not ferment properly, dilute with other feedstuffs and/or consider specific components/additives that may help. Silages with a high level of butyric acid should not be fed to pregnant or transition cows, and feeding to other milking cows should be managed so that butyric acid intake is no higher than 50 grams per head on a daily basis.

Work with your nutritionist to correctly sample your feeds to obtain accurate test results to help manage any issues and find the specific cause of the problem.



Renato Schmidt (left), Ph.D., is Forage Products Specialist with Lallemand Animal Nutrition. Contact him via e-mail: or phone: 402-850-8089.

Bob Charley, Ph.D., is Forage Products Manager with Lallemand Animal Nutrition. Contact him via e-mail: or phone: 414-336-9549

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