of Chapter 3. Samples of fresh duckweed were frozen in September 2015. Two samples were offered to Nutricontrol in Veghel (Netherlands) for analysis of their chemical composition. A composite sample was also offered to ILVO in Ghent (Belgium) for the analysis of the rumen breakdown characteristics and the in vitro digestibility of the energy components. This involved an analysis of the entire composition - dry solids, raw protein, raw fat, raw cellulose, raw ash, NDF, and sugar. Minerals were also analyzed, as were the patterns for fatty acids and amino acids, and several important characteristics relating to food safety. In 2011 Van Liere et al. executed a broad-based analysis to examine the possible risks to food safety associated with algae in combination with the use of minerals coming from manure. Experts carried out an initial assessment of possible risks related to duckweed cultivation using manure derived minerals (table below). Risk Prion diseases and BSE Viruses Hormones Dioxin Blue algae Residues of animal medication Anthrax Result It can be assumed that this is no longer a threat, given that no new cases of BSE have occurred in the Netherlands in the last few years, and because BSE affects only older animals. As long as the material remains on the premises of the farm, this does not have a high priority. This risk is not present either, as no hormones are used. Could be a risk because of the use of additives and incorrect drying of the duckweed. This toxic substance can be formed in stagnant water. As long as the duckweed pond is not stagnant, there will be no danger. This risk is not great in this situation, where there is a normal use of medicine. Low risk, as this disease does not occur at this farm. However, attention should be paid to the possible presence of dead rats or mice in the manure. Heavy metal content was below detection levels, with the exception of arsenic in one of the two samples. However, that result was also below the norm for GMP+. No salmonella was found in any of the samples. The quantities of Enterobacteriaceae were on the high side, though, but the upper limits were not exceeded. Of all the feed digested by ruminants, an average of 70% is broken down in the rumen. Bacteria produce volatile fatty acids and microbial protein in particular, which are digested in the rumen or small intestines, and released for the metabolism of the animal and for building up flesh and fat. Important nutrient features for growing ruminants are the net available energy (VEVI), rumen degradable protein (DVE), degraded protein (OEB), and fermentable organic matter (FOS). Neutral detergent fibre (NDF) is important for stability in the rumen. In the light of the high variation in the three samples investigated, an average result was used for calculating the rations. The optimization of the rations was carried out with a limited number of nutrients and a limited number of ingredients. The duckweed samples had low dry matter content. They contained more protein and ash in comparison to the information in literature. 123 Pagina 130
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