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

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 stimulus and corresponding ensiling temperatures. Commercial inoculants in liquid media were exposed to heat stimulus for 24 h at 30°C (low heat stimulus: LHS) and 40°C (high heat stimulus: 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°C and 45°C. Mini silos containing Inoculant 11 (Pediococcus pentosaceus 12455 and Lentilactobacillus buchneri (formerly designated Lactobacillus buchneri) 40788 had the lowest pH when ensiled at 45ºC regardless of prior heat stimulus 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 stimulus. In conclusion, prior exposure to heat stimulus 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 provide initial evidence that heat acclimatization of silage inoculants warrants further investigation for industrial and scientific agricultural applications.