Highlights of progress in silage conservation and future perspectives

Abstract

Forage is the basis of ruminant nutrition, but forage production has a seasonal pattern. This is due to unfavourable growth conditions during winter (temperate climates) and during the dry season (Mediterranean climates). To overcome seasonal fluctuation and prevent shortage of animal feed, forage conservation has been practiced by farmers for centuries. To prevent spoilage of freshly harvested plant tissues, various options are available. Microbiological processes leading to decay can be stopped by drying or by acidification. Traditionally, grassland plants and forage crops such as lucerne were conserved through hay making. Ensiling of forages is a microbial process that relies on the generation of lactic acid by bacteria under anaerobic conditions. As a result of technological innovations, such as the invention of plastic and mechanisation, ensiling became popular among farmers. Silage making does not require prolonged periods of dry weather that are needed for hay making. Ensiling is an important means of preserving crops that was practiced initially mainly in temperate climates of the Northern Hemisphere, but nowadays is also widespread in tropical climates.Silage production is important in animal production systems across all climate zones. The demand for high-quality silage to provide conserved forage feeds for livestock is growing in importance as competition increases for limited arable land.Fermented forage substrates now also play a role for purposes other than ruminant feed, providing substrates for biogas production and for bio-refineries, as illustrated in this issue. Developments in silage conservation technologies in the past five decades, reviewed by Wilkinson and Rinne (2018), have led to increased speed of physical and microbiological processes. Current research themes include development of technological innovations during the harvest process such as shredding and leaf stripping devices, and their implications for silage quality and fermentation. Silage fermentation is a dynamic microbial process involving the acidification of the forage by lactic acid bacteria activity in order to stabilise the biochemical and microbial constituents. Silage fermentation quality depends on the microbial communities and their succession as well as the fermentative metabolites in the ensiled material. Advances in molecular biology are providing new insight into the complexity and diversity of microbial populations during ensiling. This will increase understanding of the role of the forage microbiome in the preservation of both silage and high-moisture forages. The traditional way to analyse silage composition includes the identification and classification of its components in categories such as protein, fat, fibre fractions, vitamins and minerals. Volatile compounds evolved from chemical processes or microbial activity can add essential features to silage quality. At the International Silage Conference that took place in Bonn (Gerlach & Südekum, 2018), scientific and technological progress in silage research acro...

Silage additives to reduce protein degradation during ensiling and evaluation of in vitro ruminal nitrogen degradability

“…It is supported by the absence of significant difference of ADIN content between treatments and control. Indeed, the occurrence of Maillard reaction results in increasing nitrogen content of acid detergent fibre (Van Soest & Mason, 1991). Given that higher temperatures are detrimental to the nutritive value of silage, practices promoting a higher temperature to induce Maillard reactions during the silage process are not good options.…”

“…However, conservation practices and treatments can save nitrogen from an excessive degradation during silo and rumen fermentations and improve its utilization by ruminants. Commercial acidifying additives, such as acids or lactic bacteria, are widely used to accelerate silage acidification and limit proteolysis (Wilkinson & Rinne, ). Also useful, tannin extracts are able to bind with proteins to form complexes and prevent protein hydrolysis both in silage and the rumen (Piluzza, Sulas, & Bullitta,; Salawu, Acamovic, Stewart, Hvelplund, & Weisbjerg, ; Tabacco et al., ).…”

Grass silage for biorefinery—A meta‐analysis of silage factors affecting liquid–solid separation

“…Ensiled grass instead of fresh grass can be used year round, which results in logistically more efficient use of green biomass (Kamm, Schönicke, & Hille, 2016) requiring a press with lower capacity as it would avoid the need to process a large amount of fresh grass in a short time. Furthermore, technologies for efficient harvesting and preservation of grass silage are well established (Wilkinson & Rinne, 2018).…”

Silage and haylage for horses

“…Technical developments in forage production methods have probably also contributed to the increased use of wrapped forages in equine nutrition, as the introduction of the big baler and bale wrapping technique made it possible to trade baled and wrapped forages as well as use such forages also on farms where daily forage consumption was comparatively low, excluding use of conventional silos (Wilkinson & Rinne, ). The idea of feeding ensiled forages to equine species is, however, not new; in , Nourse concluded from experiments that maize silage was a suitable feed for horses and mules if the animals were given time to adapt to the feed.…”