Recovery of Propionic Acid (%)


PHOTO: DEVENISH


Managing moisture in animal feed production


Moisture can be lost during the grinding and pelleting process, resulting in lower moisture content compared to formulated levels. Not dealing with the issue of shrinkage can result in huge financial losses. So how can moisture be managed during the feed manufacturing process?


BY AMELIA DU PREEZ, TECHNICAL ADVISOR, DEVENISH T 91 90 89 82 80 77 75 70 4 8 Propionic acid esterified to glycerol 22 Time (weeks)


Propionic acid buffered with salt 12


16 20


he increase in the world population and the de- mand for livestock products have resulted in an in- crease in intensive livestock production. This, in turn, has led to an increased demand for safe raw


feed materials. The pandemic has highlighted the importance of food safety and security. However, due to climate change, the animal feed production system may face a higher frequency of fungal contamination. This can be as a result of unusual rainfall patterns, droughts, and shifts in temperature and humidity. Zoonotic bacterial pathogens such as Enterobacteriaceae also threaten food safety and security.


Economic losses due to poor feed safety Enterobacteriaceae and mould-infested animal feed has a detrimental effect on animal health and performance, causes significant economic losses, and has adverse effects on human health. Enterobacteriaceae, such as Salmonella, may disturb the bird’s gut health, leading to poor growth and diarrhoea. As the pathogen remains in the intestinal tract, it is


Figure 1- Stability of propionic acid from SmartMoisture. 100


94 93 92


continuously being shed into the environment and continuously re-contaminating the environment. Moulds reduce the nutritive value of feeds, reduce the palatability of feeds, and the spores may cause an immune response. Some moulds, such as Aspergillus, Fusarium and Penicillium, produce secondary fungal metabolites called mycotoxins. These mycotoxins may accumulate in the liver and long exposure to low levels will negatively impact animal production.


The proliferation of microorganisms Bacterial pathogens and moulds are widespread and cannot be entirely eliminated. They have adverse effects on animal health and performance resulting in financial losses and can be transmitted to humans. It is important that these organisms are controlled from pre-harvest right up until the animals consume the feed. The rate at which moulds and bacteria grow during feed processing and storage depends on factors such as pH, temperature, oxygen availability, and most importantly, water activity of the feed. Moisture content of feed merely describes how much water is in the product. Water activity describes how much of that water is free and therefore available to microorganisms for growth. Hot temperatures cause water to migrate during storage, while humid conditions will result in condensation, both resulting in higher activities of free water. The growth of microorganisms will be hindered when the water activity of a feed reaches below 0.9 for most bacterial pathogens and below 0.6 for most moulds. By managing the water activity of feed during processing and storage, we can reduce the proliferation of microorganisms and ensure feed safety. Heat-treatment steps can kill bacterial pathogens such as Salmonella, but moulds are stable and won’t be destroyed. This has necessitated the need for alternative solutions.


Managing moisture in feed production Shrinkage and milling loss results in huge financial losses for feed mills. Animal feed can lose up to 3% moisture during processing, so moisture management is vital. Untreated free water cannot simply be added to animal feed during processing as it will not be optimally absorbed by feed particles and will be easily driven off creating problems such as feed build-up. Free water will also increase water activity levels making the environment more favourable for microbial growth.


▶ FEED SAFETY | APRIL 2022


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