Fungistatic Compounds in Broiler Production: 2. Effect on Feed Microflora

Abstract

Feed samples were examined from five broiler experiments using either sorbic acid, gentian violet, or calcium propionate as fungistatic compounds. Feed samples were taken from storage and from the feed troughs of each pen at 0, 2, 4, 6, and 8 weeks of broiler age. Samples from the same diet and sampling location were composed and mixed. Serial dilutions of these mixed samples were made and plated for aerobic, anaerobic, and mold and yeast counts. The initial feed microflora counts varied greatly with their ingredient sources. In general, the log anaerobic counts were slightly lower than those of the aerobic counts with a difference of less than one log cycle. The addition of the fungistatic compounds had no consistent effect on the aerobic, anaerobic, and mold and yeast counts. After two and four weeks of feeding, a steady increase in total aerobic and anaerobic counts was observed for feed samples obtained from feeder troughs; however, there was no increase in mold and yeast counts. Increasing the moisture content of the feed to approximately 15% had no effect on the microflora counts. No visible mold growth or caking problems were detected for any feeds after four weeks of storage. In one experiment, sorbic acid consistently reduced the coliforms and the lactobacillus counts for feeds sampled from feed troughs.