Using Temperature to Control Pathogens

Temperature is considered one of the most important environmental factors affecting growth and survival of microorganisms. The optimum temperature for most pathogens is around 98°F. If temperatures rise to high levels (above 131°F), pathogen growth rate sharply declines, proteins denature and thermal breakdown of the cell membrane occurs resulting in cellular death.

In-house windrow composting of built-up broiler litter has been adopted in some production complexes as an attempt to reduce or destroy pathogens during flock downtime. If properly conducted, the process can achieve adequate temperatures for pathogen control; however, careful management is required for this process to work. The nature of modern litter management strategies and relatively short downtimes between broiler production flocks create challenges for successful adoption of in-house litter windrowing.

Litter management strategies attempt to achieve a dry litter, which conflicts with achieving optimal moisture content for effective windrowing. For windrows to properly heat and achieve pathogen kill, adequate C:N ratios (25:1) and moisture (at least 40%) are necessary. Normal litter has a C:N ratio of 15:1 and a moisture content around 20-25%.

These conditions are not conducive for effective windrowing, thus temperatures (which often go unchecked) do not reach adequate levels. Mixing wet litter into the windrow to provide the necessary moisture may only redistribute disease-challenged litter throughout the house.

The high level of ammonia produced both during and following the windrow process presents another challenge. Proper management must be in place so that ammonia concentrations after windrowing do not negatively affect the health of the next flock. Following windrow spreading, houses should be given sufficient time, with proper ventilation, to purge ammonia prior to chick placement. Thus, extended down times are required in order to manage the ammonia levels post windrow leveling.

Finally, windrowing litter degrades carbon bedding material to a fine particle size. Over time, windrowed litter becomes too fine and loses its absorption characteristics. Instead of moisture caking at the surface, it migrates to the pad to create deep litter ammonia challenges.