Microbiology of Sanitized Broiler Hatching Eggs Through the Egg Production Period

Nest-clean and dirty eggs were sampled monthly across the productive period of a commercial broiler breeder flock. Eggshells and membranes were examined for total aerobic bacterial and Enterobacteriaceae counts per egg. Paired nest-clean and dirty eggs were spray sanitized in a two-stage commercial egg sanitizing machine (a chlorine detergent wash followed by a quaternary ammonia sanitizing spray) and tested for bacterial contamination. As the flock aged, numbers of bacteria per nest-clean egg fluctuated without a noticeable trend (from log10 4.1 to 5.3 aerobic bacteria). Bacterial populations were significantly lower on sanitized eggs (log10 0.8 to 3.2 cells total aerobic bacteria and 2 to 5 cells Enterobacteriaceae per egg) regardless of hen age. Those eggs classified as dirty had visible fecal contanmination and higher bacterial numbers than nest-clean eggs (log10 5.9 to 7.6 cells total aerobic bacteria per egg). After sanitization, previously dirty eggs had bacterial populations comparable to those of sanitized nest-clean eggs. When eggs were examined in the hatchery at transfer, sanitized dirty eggs were still microbiologically indistinguishable from sanitized net-clean eggs, though both groups had higher bacterial contamination levels than had been observed in samples taken immediately following sanitization.