Influence of heat stress and ensiling temperature on growth and performance of silage inoculants

Authors: CHIBUOGWU, MAXWELL - Oak Ridge Institute For Science And Education (ORISE); Panke-Buisse, Kevin; GRITTI, VIVIANE - Universidad De Sao Paulo; NUSSIO, LUIZ - Sao Paulo State Agency For Agribusiness Technology (APTA)

Submitted to: Animal Feed Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/17/2025
Publication Date: 7/18/2025
Citation: Chibuogwu, M.0., Panke-Buisse, K., Gritti, V.C., Nussio, L.G. 2025. Influence of heat stress and ensiling temperature on growth and performance of silage inoculants. Animal Feed Science and Technology. https://doi.org/10.1016/j.anifeedsci.2025.116446.
DOI: https://doi.org/10.1016/j.anifeedsci.2025.116446

Interpretive Summary: Many types of desirable lactic acid bacteria (LAB) commonly found in silage thrive at temperatures around 30 ºC. In contrast, some spoilage bacteria prefer warmer temperatures and can even grow above 45 ºC. This difference in temperature preferences between helpful LAB and harmful spoilage bacteria raise concerns about how higher temperatures might impact silage and the impact of warmer temperatures on LAB inoculants and their performance after exposure to heat stress is unclear. This study aimed to understand how LAB isolates react to heat stress and how stressed LAB contributes to the fermentation efficiency of silage. The findings from the study revealed that prior heat exposure affected how well the silage inoculants performed both in liquid culture and during the silage process. Specifically, some inoculants exposed to high heat stress had lower pH levels in silage fermented at higher temperatures. They showed different fermentation patterns compared to those exposed to lower heat stress or the control. For example, we detected greater lactic acid concentration in silage inoculated with one high heat-stressed LAB isolate in higher ensiling temperatures compared to samples with the same inoculant but not heat-stressed and in normal ensiling conditions. Overall, this study shows that heat stress plays a role in determining how inoculants contribute to silage fermentation. Additionally, different inoculants react differently to heat stress, some more positively than others during fermentation. In general, this body of work indicates that further research into the mechanisms of how heat affects silage bacteria could be vital for both industrial use and scientific understanding.

Technical Abstract: The main objective of this research was to observe patterns of fermentation between silages inoculated with lactic acid bacteria exposed to high, or low, levels of heat stress and corresponding ensiling temperatures. Commercial inoculants in liquid media were exposed to heat stress for 24 h at 30 ºC (low heat stress: LHS) and 40 ºC (high heat stress: HHS) to test growth. All inoculants showed significant inhibition of growth in liquid culture at 40 °C compared to 30 °C. Heat-challenged inoculants were then applied to mini silos of chopped, whole-plant corn incubated at 30 ºC and 45 ºC. Mini silos containing Inoculant 11 (Pedi coccus pentosaceus 12455 and Lactobacillus buchneri 40788) had the lowest pH when ensiled at 45 ºC regardless of prior heat stress level but was significantly lower in the HHS group. Despite their poor performance in liquid culture prior to ensiling, Inoculants 6, 7, 10 and 11 all showed significant improvement in silage pH after high-heat stress. In conclusion, prior exposure to heat stress produced varied effects on the performance of silage inoculants in liquid culture and during ensiling. Exposure to HHS resulted in lower silage pH values and varied fermentation profiles for some inoculants when compared to LHS or uninoculated controls. The results of the current study provides initial evidence that heat acclimatization of silage inoculants warrants further investigation for industrial and scientific agricultural applications.