Controlling aerobic stability of silage based total mixed rations

Total mixed ration (TMR) is a feeding method for ruminants. Silage is the most important component of a TMR in Finland. TMR provides favorable conditions for microbial growth, which can cause rapid spoilage and spontaneous heating of the feed. MSc Arja Seppälä studied in her doctoral dissertation the factors contributing to heating and ways to control the spoilage of the TMR. Trials were conducted at Natural Resources Institute Finland (Luke).

The objective of this thesis was to explore the factors affecting TMR stability especially by varying both silage additive and silage dry matter concentration. The ensiled crops were a mixture of grass, timothy and meadow fescue, and faba bean-wheat and field pea-wheat whole crops. The grass was ensiled at two dry matter levels. Aerobic stability of both the silage and the TMR was measured by following the temperature rise in the feed materials during aerobic exposure.

Silage aerobic stability was shown to be a major factor contributing to TMR stability, the size of the effect of silage additive being 13 to 82 hours within crop. The preservative added into TMR at the time of mixing improved TMR stability by 1.5 to 41 hours depending on the microbial status of the TMR and the application level of the preservative. Low yeast count of the TMR was related to good stability. Poor hygiene reduced TMR stability remarkably and chemical TMR preservatives can improve TMR stability especially effective when the initial number of spoiling organisms is low. The results of MSc Arja Seppälä's thesis provide information needed for improvement silage and respective TMR aerobic stability.

MSc Arja Seppälä, will defend her doctoral dissertation entitled "Controlling aerobic stability of silage based total mixed rations" in the Faculty of Agriculture and Forestry, University of Helsinki, on 24 September 2020 at 12 o’clock. The public examination will take place at the following address: Metsätalo, Sali 6, Unioninkatu 40, Helsinki. Associate Professor Elisabeth Nadeau, Swedish University of Agricultural Sciences, will serve as the opponent, and Professor Aila Vanhatalo as the custos. The defence can also be followed remotely using the following link : 

The dissertation is  available in electronic form in E-thesis service.

Contact: Arja Seppälä,