Indigenous feed microflora and Salmonella typhimurium marker strain survival in poultry mash diets containing varying levels of protein

The effect of varying concentrations of different protein sources on the survival of a Salmonella typhimurium marker strain resistant to both novobiocin and nalidixic acid in nonsterile poultry mash diets was determined. A dry inoculum containing a primary poultry isolate of S. typhimurium was used to evaluate survival in mash containing one of two protein sources, soybean meal or meat and bone meal, at five concentrations (100, 150, 200, 250 and 300 g crude protein kg−1 mash) and stored at room temperature (21±1°C) for 56 days. In general, aerobic enumerations recovered from diets containing meat and bone meal were greater than those from diets containing soybean meal excluding day 0 and 56 (P<0.05). During the 56-day period a reduction by approximately 0.5 log10 colony forming units Salmonella g−1 mash was observed. The differences of Salmonella survival between soybean and meat and bone meal based diets was not consistent among 10 sampling points. No significant differences of either aerobic bacterial populations or Salmonella were observed for the five concentrations of protein for each source (P≥0.05). However, large numbers of this organism survived at all protein concentrations well beyond typical storage times.