Different experimental designs in testing of silage additives

Quality of silage fermentation and consequent aerobic stability of silages is still a common problem of many types of silage. Experimental testing of silage additives is commonly conducted under routine ensiling condition with properly consolidated forages and airtight silos. Consequently, it is not surprising that results of these trials do often not display a potential of a product in the agricultural practice. Punctures and other damages of silo cover as well as uneven forage consolidation in a silo are common. These defects make ensiling conditions more difficult and challenge a silage additive to fulfil its purpose. It has been observed that silos which were not tight under the fermentation process are more prone to be aerobically unstable (Jonsson & Pahlow, 1984). Based on this observation, a German system for evaluation effects of silage additives (DLG, 2009) applies a design where silage additives are tested under difficult ensiling condition by two times of air ingress into a mini-silo for 8-12 hours combined with a very low packing density. This condition, however, does not properly reflect silo un-tightness. It is more common that a silo is exposed to a weak but constant air ingress. This condition is more closely reflected by a design with a 2-hours weekly air ingress used by Pauly and Hjelm (2015) in testing efficiency of silage additives on conservation of crimped maize. Therefore, the objective of this study was to compare the impact of ensiling challenged by weekly aeration in a silage additive test to improve forage conservation.