Dual sensor measurement shows that temperature outperforms pH as an early sign of aerobic deterioration in maize silage

Guilin Shan,Yurui Sun,Ismail-Hakki Acir,Christian Maack,Manfred Trimborn,Wolfgang Buescher,André Lipski,Fabian Kuellmer,David A Grantz,Ye Wang

doi:10.1038/s41598-021-88082-1

Abstract

High quality silage containing abundant lactic acid is a critical component of ruminant diets in many parts of the world. Silage deterioration, a result of aerobic metabolism (including utilization of lactic acid) during storage and feed-out, reduces the nutritional quality of the silage, and its acceptance by animals. In this study, we introduce a novel non-disruptive dual-sensor method that provides near real-time information on silage aerobic stability, and demonstrates for the first time that in situ silage temperature (Tsi) and pH are both associated with preservation of lactic acid. Aerobic deterioration was evaluated using two sources of maize silage, one treated with a biological additive, at incubation temperatures of 23 and 33 °C. Results showed a time delay between the rise of Tsi and that of pH following aerobic exposure at both incubation temperatures. A 11 to 25% loss of lactic acid occurred when Tsi reached 2 °C above ambient. In contrast, by the time the silage pH had exceeded its initial value by 0.5 units, over 60% of the lactic acid had been metabolized. Although pH is often used as a primary indicator of aerobic deterioration of maize silage, it is clear that Tsi was a more sensitive early indicator. However, the extent of the pH increase was an effective indicator of advanced spoilage and loss of lactic acid due to aerobic metabolism for maize silage.

Highlights

Aerobic deterioration of silage is unavoidable, during feed-out[1,2,3] because, once a silo is opened, air freely accesses the exposed silo face
Since samples sent to a forage laboratory for plate-culture counts create assessment delays of several days, an early indicator of aerobic deterioration that can be instantly measured in situ is needed to allow decisions to be made on commercial silage masses in real time
Relationships between pH and T si determined in situ following aerobic exposure of maize silage; and (3) evaluate aerobic loss of lactic acid associated with the temporal courses of Tsi and pH change

Summary

Introduction

Aerobic deterioration of silage is unavoidable, during feed-out[1,2,3] because, once a silo is opened, air freely accesses the exposed silo face. Previous studies of aerobic responses of silage pH used laboratory minisilos[7,15,16,17,18] and farm silos[5,10,19,20,21,22,23], both with invasive sub-sampling followed by liquid extraction of silage samples. Such ex situ pH determination may interfere with silage conditions, including the anaerobic environment, and is typically completed at daily (or longer) time intervals, which obscures important short term dynamic changes. Comparison of the silage treatments per se was not the study purpose

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