The impact of the quality of silage on animal health and food safety: a review.
This paper reviews the microbiological aspects of forage preserved by ensilage. The main principles of preservation by ensilage are a rapid achievement of a low pH by lactic acid fermentation and the maintenance of anaerobic conditions. The silage microflora consists of beneficial micro-organisms, i.e. the lactic acid bacteria responsible for the silage fermentation process, and a number of harmful micro-organisms that are involved in anaerobic or aerobic spoilage processes. Micro-organisms that can cause anaerobic spoilage are enterobacteria and clostridia. Clostridium tyrobutyricum is of particular importance because of its ability to use lactic acid as a substrate. Silage-derived spores of C. tyrobutyricum can cause problems in cheese making. Aerobic spoilage of silage is associated with penetration of oxygen into the silage during storage or feeding. Lactate-oxidizing yeasts are generally responsible for the initiation of aerobic spoilage. The secondary aerobic spoilage flora consists of moulds, bacilli, listeria, and enterobacteria. Mycotoxin-producing moulds, Bacillus cereus, and Listeria monocytogenes in aerobically deteriorated silage form a serious risk to the quality and safety of milk and to animal health.
Driehuis
F
F
NIZO Food Research, Ede, The Netherlands. driehuis@nizo.nl
Oude Elferink
S J
SJ
D000827:Animal Welfare; D000818:Animals; D001420:Bacteria, Aerobic / Q000254:growth & development / Q000378:metabolism; D001421:Bacteria, Anaerobic / Q000254:growth & development / Q000378:metabolism; D002417:Cattle; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D007778:Lactobacillus / Q000254:growth & development / Q000378:metabolism*; D012756:Sheep; D012820:Silage / Q000382:microbiology* / Q000592:standards