On Farm Silage Audit

As ensiled forages represent up to 50% of the dairy cow’s diets, ensuring the silage produced is of the best quality possible is essential in controlling feedcost and driving profitability.

It’s all too easy to lose significant levels of forage from harvesting to the feed bunker. Dry Matter losses can range from 10 to 30% of the harvested crop. Taking control of the silage making process through simple and practical applications can help reduce these losses significantly.

To assess silage quality and better target areas where improvements could have a practical benefit to producers, Lallemand Animal Nutrition developed a silage audit method based on a set of practical evaluation criteria, measuring pH, temperature, density and packing of silage silos. The audit was carried out on over 140 farms.



The results of the audit showed that the weakest point on most of the farms is silo density. According to the audits, silo densities were low, with only 36% of the bunkers packed correctly (>240 kg DM/m3 for corn/maize). Silages packed at lower densities will have more retained air in the silo. This will cause the silage to ferment poorly which in turn results in higher dry matter losses and significantly increases the risk of wastage through aerobically unstable silage.

High densities are obtained when good silage practices are combined with the correct silo parameters. All farmers can achieve a proper density regardless of the equipment used for harvesting, as long as they respect the adequacy in between packing capacity and the other parameters. We have talked  previously about how to construct corn/maize silo with correct packing density in one of our articles.

Overall, on-farm silo audits are valuable tools. Monitoring the forage quality at any moment during the preservation process is the only real way to assess the given situation.


Lallemand Animal Nutrition does not purport, in this guide or in any other publication, to specify minimum safety or legal standards or to address all of the compliance requirements, risks, or safety problems associated with working on or around farms. This guide is intended to serve only as a beginning point for information and should not be construed as containing all the necessary compliance, safety, or warning information, nor should it be construed as representing the policy of Lallemand Animal Nutrition. No warranty, guarantee, or representation is made by Lallemand Animal Nutrition as to the accuracy or sufficiency of the information and guidelines contained herein, and Lallemand Animal Nutrition assumes no liability or responsibility in connection therewith. It is the responsibility of the users of this guide to consult and comply with pertinent local, state, and federal laws, regulations, and safety standards.

Leave us a comment

Dear Bernard,
The production of nitrogen dioxide (silo gas) does not mean that the farm has done something wrong. The gas is produced when the growing plant is harvested and it has not utilized all of the nitrogen that it has adsorbed for growth. After periods of stress (temperature or drought) all plants ‘luxuriously’ take up nitrogen and store it for growth – if not all of the nitrogen has been used when the forage is ensiled it will be released as ‘silage gas’. Very often we do not even notice that this has occurred because the gas is adsorbed into the body of the silage, but sometimes the gas escapes from the ensiled forage because the silo is not closed yet or because the silo is not perfectly sealed.

Silo gas is produced as the pH fall during the first days of ensiling. If the farm has a current issue then I am happy to speak directly with the farm and can be reached on +44 (0) 7584 127910 (Gordon Marley) and can be reached on this number, WhatsApp or gmarley@lallemand.com

The most important point with silo gas is ‘managing the issue’ as opposed to avoiding the issue. We can not adjust the environment so we can not adjust how the plant is going to react to the season.

If silo gas is being produced all staff and animal must be kept away from the bunker until gas is no longer produced. Silo should be sealed at earliest opportunity after filling is complete with a minimum of a 1m overlap of plastic. If anyone is exposed to silo gas they must seek immediate medical attention.