Effects of dietary n-3 polyunsaturated fatty acids and ... - FINS

1 st WorkshopXIII International Feed Technology Symposiumapplied technological procedures and stability of the product in the storage conditions.Animal feeds can serve as a carrier for a wide range of microbial contaminants such asbacteria, yeasts, molds and their toxic metabolites (mycotoxins) [11]. Such contaminantshave been shown to influence animal performance adversely and to compromise thesafety of animal products.The growth and sporulation of microorganisms as well as toxin production to a largeextend are depending from moisture content of the substrates (feed ingredients andcomplete feed mixtures) as well as moisture and the relative humidity in the storageenvironment. It is known that minimum water activity (a w ) is: for bacterial growth a w =0.90, for yeast growth a w = 0.85 and for fungal growth a w = 0.65 [8].One of the contemporary feed manufacturing processes for reducing presence of themicroorganisms in feed is thermal processing (pelleting) [5]. This process involvesmixing steam with the feed, pressing the mixture through a die, and cooling the pelletsafterwards in order to remove heat and moisture. If the pelleting process is donecorrectly added 3-5% moisture in the form of steam is removed from the feed beforeshipment. However, if this excess moisture is not removed after cooling the pellets, moldgrowth will be encourage since pelleted feeds with higher water content are warmer andtheir storing in a cool bin will cause water condensation on the inside of the bin.Although pelleting of fodder has been shown to reduce mold and bacteria count by thefactor of 100 to 100,000 many fungal spores remain in the feed after it was pelleted. Inright conditions the remaining spores can grow and produce mycotoxins. Thus, pelletingprocess delays, but does not prevent, the onset of fungal growth.So, thermal processing alone will not guarantee the elimination of microorganisms. Onthe other hand, contaminated incoming ingredients, inadequate housekeeping measures,insects, rodents and food traffic through the feed mill can lead to recontamination of thefodder.The goal of this investigation was to determine influence of pelleting procedure of calvesmixture on microbiological and mycotoxicological proprieties of mixture during 150days storage period.MATERIAL AND METHODSSamples. Investigated powdered mixture (11.29% moisture) was produced in FeedMixture Industry, Padinska Skela. Components were mixed with horizontal mixer(Buhler), of 3000 t capacity. Pelleting of the same mixture was done by the press of thesame manufacturer at 75 o C. Pellet diamether was 4 mm, lenght 4 to 6 mm, and moisture11.13%. Composition of the mixture is shown in Table 1.Immediately after the production of feed and pelleting, the samples for microbiologicaland mycotoxicological analysis were taken (day 0). Feed mixtures were kept in nylonbags during 150 days and sampled periodically (November 2008 – March 2009), at 20cm above the floor, in ventilated, semi-dark and dry room. Average room temperaturewas 18 0 C (7-22 0 C).Microbiological investigations were performed according to Regulations on maximalquantity of harmful materials and ingredients in fodder [17]. Total count of bacteria,molds and yeasts as well as identification of pathogenic microorganisms (E. coli, coagul.positive Staphylococcus spp., Proteus spp., Salmonella spp., sulphito-reducing111