Q: I am getting customer complaints about mold, but my moisture levels are within target. What could be the cause?
By: Jose Ramirez, Technical Director
Feed moisture is incredibly complex, and for many feed mills, it is hard to achieve targeted moisture.
The struggle you are describing is not uncommon. Mold requires water, food, moderate temperature and oxygen to grow. Feed meets all of these needs. As you have already recognized, mold growth is not surprising when feed moisture is higher than targeted, but it is more confusing to reconcile in feeds at or below target. Many would attribute this mold growth to raw material quality, but you are on the right track, thinking it may still have something to do with feed moisture. Water in feed can be either retained or free. Free water in feed is more available for utilization by molds.
Moisture retention in feed can be assessed through a combination using two different tests, moisture measurement and water activity. Moisture measurement accounts for the total amount of water in feed. To assess for free water, you would need to measure the water activity. Binding water to feed is multifactorial. The research behind feed milling has taught us that conditioning promotes gelatinization, which aids in moisture retention. However, water also has a high surface tension due to hydrogen bonding, meaning that water binds tightly to itself because it is easier than binding to particles such as those found in feed. Adjusting moisture to achieve an optimized target within a formula requires us to understand the behavior and role of moisture during the conditioning phase.
When one adjusts moisture by simply adding water, moisture is unevenly absorbed, leaving areas of retention and free water throughout the batch. Maxi-Mil helps producers achieve optimal moisture targets and prevent mold growth by promoting the retention of water in feed. Maxi-Mil has been specifically designed to reduce the surface tension of water, increasing its ability to bind to feed. In addition, tailored application systems promote even distribution of moisture within the diet and promote uniformity in the finished feed.