Examination of stockfeeds for Salmonella

Of 100 stockfeeds examined for Salmonella 45 were positive by pre-enrichment followed by selective enrichment of 10 x 25 g samples. Forty-three were positive by selective enrichment of pooled aliquots of the pre-enrichment broths from the 10 x 25 g samples. Aliquots of the pre-enrichment broths from the 10 x 25 g samples of 77 of the feeds were stored at 4 degrees C and retested after 6 days. One hundred and ten of these (770) subsamples were found to contain salmonellas initially, and 107 were found to contain salmonellas after storage for 6 days. The testing of feeds by the examination of multiple 25 g samples and pooled pre-enrichment broths is recommended. Aliquots of the pre-enrichment broths may be stored at 4 degrees C for 6 days and retested if an estimation of the numbers in the feed is required. Further pre-enrichment after cold storage is not required.