Effects on Aerobic Processes at Silage Faces

Abstract

In animal nutrition, one of the most important and indispensable requirements is high quality of feed. Especially the staple feed, which builds the basic feed for animals’ rations, has to fulfill high quality criteria. In most cases, silage is used as staple feed for productive livestock. The conservation of forage as silage, offers the opportunity of conserving nutrients and energy in an adequate way. The aim of silage production is to obtain a product which contains a maximum of nutrients and energy originating from the fresh plant. The production of high quality staple feed is critically important because the conservation of plant material represents a central cost factor for agricultural businesses. Aerobic-induced silage reheating is responsible for energy and nutritional losses in this preserved staple fodder. If the plastic cover of the silage is damaged or opened for feed-out, silage gets in contact with oxygen from the ambient air, which endangers the nutritional value.<br /> Since different methods for laboratory experiments with silage are used, the results are often neither comparable to each other nor to farm conditions. The amounts of losses caused by aerobic deterioration determined in laboratory experiments are different from losses observed on farms. One of the goals of the conducted project was the development of a new optimized method for trials investigating silage under aerobic conditions. The developed test method was used to quantify the physical, biological and chemical influencing factors on aerobic stability of silage. The test method has a practical orientation and simulates the circumstances of a clamp silo and is therefore similar to farm conditions. It includes temperature measurements, gas sampling and gas analyses and laboratory analyses of silage samples. In the further course of the investigations, the method was used for the trials conducted. The objective of the first study implementing the new method, was to investigate the effect of the physical factor ‘bulk density’ on temperature profiles, microbial respiration activities and DM as well as energy and nutritional losses during the reheating of maize silage. In conclusion, the results of this study showed that high density of plant material is an important physical factor supporting the aerobic stability at the open silage face. Furthermore, the compaction has a great impact on the reduction of the silage temperature during the feed-out period. Additionally, high density reduces microbial respiration activity in silage, can potentially reduce mass losses and it preserves DM, nutrients and energy during the aerobic feed-out period. <br /> Based on these findings, the following study investigated the effects of different factors (biological, chemical and physical) on silage during aerobic conditions. As a physical factor, different bulk densities were adjusted again to get more insights concerning this factor. Additionally, two different biological inoculants were added to the silage and a chemical additive was also used. The impacts of the different factors were compared to each other. The findings confirmed high bulk density to improve the aerobic stability of maize silage. The chemical additive prevented silage from deterioration very effectively and inhibited microbial heat production even during a period of ten days of air exposure. Higher density had no additional positive effect on silage in aerobic conditions when using the chemical additive. In this case, the high density offers the advantage of smaller volume of the silo stock, which may be positive if storage capacity is limited. The silages treated with biological inoculants also did not undergo reheating. Thus, the biological inoculants could also successfully prevent silage from aerobic reheating. Furthermore, higher density had no additional positive effect on silage in aerobic conditions when using the biological additives. The comparison of the different factors shows that the influence of the additive and inoculants used is high and the physical factor bulk density also had positive influence on aerobic stability. <br /> To transfer results into practice as a final step, silage density was investigated on a farm in a clamp silo. Therefore, packing quality was precisely assessed by a penetrometer-based mapping system which was especially developed for measurement at the silo face. The experiment was conducted in a maize bunker silo. The density distribution of such silos shows a big variation between different parts of the silo. The spoilage risk for a bunker silo, especially in the upper parts or in the side region with low density, is rather high. Developing a penetrometer-based mapping system was the major objective of the fourth study and was successfully met. The developed penetrometer mapping system offers the opportunity to represent the packing density and is thereby able to detect deficits in compaction. The mapping system may be beneficial for the rapid assessment of aerobic deterioration risks in bunker silos.