ISSUE FOCUS 40 FEED & ADDITIVE MAGAZINE May 2023 feed ingredients exported to the said country. Since microbial quality of raw materials can be contaminated by disease-causing pathogens, what are the things a feed producer can do? WAYS TO MANAGE MICROBIAL CONTAMINATION In managing contamination, producers should start with monitoring the quality of incoming ingredients in terms of microbial contamination like Salmonella, Enterobacteria, E. coli and molds. Eventually, major ingredients and their suppliers can be assessed on risk of contamination. Partnership with suppliers of good quality ingredients will help in managing contamination. Since there is always risk of contamination as new batches of ingredients go inside the feed mill, review of cleaning practices and their frequency is integral in managing contamination. Special emphasis should be taken care of on “hot spots,” or areas where contamination tends to build up as days progress. In machines like mixers, conditioners and coolers, regular cleaning frequency is necessary to reduce spread of contamination. It is also important to control dust accumulation in all areas of feed mill as it can be a vector of pathogenic bacteria and spread inside the mill. In most cases, use of feed additives with antibacterial properties like organic acids will help reduce the risk of contamination – especially for mash and young animals. For decades, acetic and citric acids have been added to food as preservatives and to inactivate foodborne pathogens. In feed and ingredients, organic acids like formic (Figure 1), propionic and blends of acids are known to be effective in a commercial scale in inhibiting growth of bacteria and molds. Thus, adding organic acids or blends of acids during cleaning or flushing of mixers may inhibit growth of pathogens in the equipment and production line. Study from Stonerock 2007 shows the inhibition capacity of an acid blend of formic and propionic acid at different dose level (Table 2). With 0.12% inclusion rate in vitro, it has already 5 log reduction against Salmonella enteritidis. Feed ingredient n1 EC2,3 n % Enterobacteriacae Salmonella Positives Brewers grains Corn Cottonseed meal Fishmeal Limestone Meat and bone meal Soybean hulls Soybean meal (47%) Wheat Whey Wheat middlings Adapted from Jones and Richardson, 2004 1Number of assays. 2Enterobacteriaceae counts = mean log10 colony-forming units per gram ± standard error. 3Standard errors were not listed if n < 5. 3 19 2 1 1 1 5 10 1 1 24 0 1 2 1 0 0 0 1 0 0 1 0 5.26 100 100 0 0 0 10 0 0 4.17 3.01 3.25 ± 0.44 2.90 0.00 0.00 0.00 4.30 ± 1.08 2.56 ± 0.60 5.61 0.00 4.10 ± 0.28 Table 1. Enterobacteriaceae counts (EC) and Salmonella contamination of feed ingredient samples
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