Silage processing and strategies to prevent persistence of undesirable microorganisms

International audienceYear-round access to good quality forage is a physiological priority for ruminants and an economic priority for farmers. Ensiling is a method for preserving moist crops based on organic acid production by lactic acid bacteria under anaerobic conditions. However, silage can be a vector for undesirable microorganisms, impairing crop preservation, animal performance or the health of both animals and humans. Major problems in silage processing are due to failure to apply good manufacturing practice (GMP). To improve silage preservation and guarantee the quality of this animal feed, silage additives such as chemicals, enzymes and bacterial agents can be employed. The purpose of the present paper is to review existing information on the desirable and undesirable microorganisms involved in silage processing, and possible methods, using GMP or silage additives, of limiting silage degradation and its economic effects and health impact on animals and humans. (C) 2013 Elsevier B.V. All rights reserved

Growth and Survival of Acid-Resistant and Non-Acid-Resistant Shiga-Toxin-Producing Escherichia coli Strains during the Manufacture and Ripening of Camembert Cheese

Growth and survival of acid-resistant (AR) and non-acid-resistant (NAR) Shiga-toxin-producing Escherichia coli (STEC) strains were investigated during the manufacture and ripening of microfiltered milk Camembert cheeses. The induction of acid resistance of the STEC strains in cheeses was also studied. Six different mixtures of AR and/or NAR STEC strains were inoculated separately into microfiltered milk at a level of 103 CFU mL−1. The STEC counts (AR and NAR) initially increased by 1 to 2 log⁡10 CFU g−1 during cheese-making. Thereafter, the populations stabilized during salting/drying and then decreased during the early stages of ripening. Exposing the STEC strains in artificially inoculated cheeses to simulated gastric fluid (SGF - pH: 2.0) reduced the number of NAR strains to undetectable levels within 40 minutes, versus 120 minutes for the AR STEC strains. AR and NAR STEC were able to survive during the manufacture and ripening of Camembert cheese prepared from microfiltered milk with no evidence of induced acid tolerance in NAR STEC strains