Quality of silages from Italian farms as attested by number and identity of microbial indicators

Abstract

This study evaluated the quality and possible hygiene risks related to farm-made silages by analysing the presence and number of micro-organisms that influence the preservation and safety in samples from four Italian regions. Lactic acid bacteria, clostridia, lactate-fermenting yeasts and propionibacteria (PAB) were isolated and identified by random amplified polymorphic DNA PCR, sequencing of the V2-V3 16S rRNA gene region, 5.8S-ITS rDNA RFLP and species-specific PCR. The Lactobacillus plantarum cluster was the most numerous and comprised strains mostly isolated from alfalfa silage. The Lactobacillus buchneri cluster, second in number, comprised isolates from both alfalfa and maize silage. Anaerobic spore formers were assigned to the species Clostridium baratii, Clostridium beijerinkii, Clostridium butyricum, Clostridium perfringens, Clostridium saccharolyticum, Clostridium tyrobutyricum and Paenibacillus macerans. Yeast isolates were identified as Candida apicola, Candida mesenterica and Pichia fermentans. PAB strains, detected only in unifeed, were all identified as Propionibacterium acidipropionici. The occurrence of spoiling micro-organisms was frequent and the possibility of contamination by potentially pathogenic clostridia was demonstrated. The results suggest the need for improved ensiling practices and appropriate control measures to safeguard the hygienic and nutritional quality of silages produced in farms.