A coordinated mycotoxin management program at a feed mill begins with a comprehensive quality assurance program. The program must include more than merely testing for mycotoxins during the receiving process. The quality assurance program must also have strategies to prevent their introduction into the manufacturing process and minimize mold growth that could produce mycotoxins during grain storage, feed processing and finished feed storage on the farm.
Supply chain monitoring
The first step to minimize the risk of mycotoxins in finished feed is to reduce the amount of mycotoxins in the raw ingredients. A feed mill should have ingredient purchasing specifications that include the maximum level allowed for each mycotoxin. The maximum levels in ingredients have historically been based on the regulatory and advisory levels set by the Food and Drug Administration. Since aflatoxin is the only mycotoxin that has regulatory action limits issued by the FDA, the maximum level for other mycotoxins are typically based on FDA advisory or guidance levels. Therefore, maximum levels for DON, fumonisins, ochratoxin, T-2 and zeralenone must be clearly outlined in ingredient specification sheets and purchase contracts.
Proper sampling and testing of inbound ingredients is the first defense to minimize the receipt of ingredients that contain mycotoxins. The USDA Grain Inspection, Packers & Stockyards Administration has recommendations for sampling rail cars, as well as flat and hopper bottom trucks as noted in the probe sampling portion of GIPSA's Grain Inspection Handbook.
Obtaining a representative sample and properly dividing the sample are two critical steps prior to analyzing the sample. Mycotoxins are typically not evenly distributed throughout a load of grain.
The study, "Testing Shell Corn for Aflatoxin, Part I: Estimation of Variance Components," reported that when analyzing corn for aflatoxin, that sampling of ingredients contributes to the most variability followed by sample preparation and laboratory analysis.
How to preserve grain quality
Molds and fungi that produce mycotoxins typically do not grow when the grain is below 12 to 13 percent moisture. Therefore, to minimize the growth of mycotoxins in stored grain, feed mills must develop standard operating procedures to keep the moisture of the grain less than 13 percent. This includes preventing insect damage, routine aeration of the grain to equalize temperatures and annual cleanout of the storage bins.
Removing the broken kernels and foreign matter prior to storage will also reduce the potential for mold growth. In addition to grain storage, interior ingredient bins should be emptied and inspected at least monthly to prevent product accumulation that could lead to mold growth, especially in the ground grain bins. If feed bins are not periodically cleaned, feed can build up on the sides, encourage mold growth and create cross contamination. This becomes a greater concern if the feed is not properly cooled after the pelleting process or if warm mash feed is sent to the finished feed bins. Thus, finished feed bins should also be inspected at least once each month and cleaned as needed.
Equipment's role in mycotoxin managemen
Equipment selection, installation, operation and preventive maintenance are important when attempting to prevent mold growth that has the potential to produce mycotoxins. Equipment should be selected to minimize cross contamination, be accessible for cleaning, and be properly sealed to prevent the entry of water from rain and snow.
Material handling equipment, such as conveyors, located outside the mill should have peaked covers to prevent water from accumulating on the covers and then running into the conveyors. The lids should always be sealed with silicone to prevent dust leaks and moisture entry. The boot of a bucket elevator should also be cleaned on a routine basis to prevent mold growth, as the product in the boot section is static and can accumulate moisture over time. Bucket elevators external to the mill should sit on raised concrete pads to prevent water from running into the boot section during a rain event. Bucket elevators located in receiving tunnels or pits should be inspected more frequently due to the fact they are located in a cool damp environment. The bucket elevator associated with a hammermill grinding system has greater potential for moisture condensation and accumulation due to the heat generated and moisture driven from the grain during particle size reduction.
Pelleted feed has the potential for mold growth after the cooling process, especially if adequate cooling was not accomplished. During the pelleting process, dry feed is conditioned with steam to temperatures in excess of 170 F, resulting in a moisture content of 15 to 18 percent. The moisture in the hot pellet is removed after the pelleting process with either horizontal or counter flow coolers. The cooling process uses fans to pull ambient air through a bed of pellets in order to remove heat and moisture.
Cooling systems must be designed and properly installed to minimize accumulation of dust and fines in the ductwork and cyclones, as well as prevent condensation of moisture on the surfaces of the equipment during the cooling process. Coolers, ductwork and cyclones should be regularly inspected as part of the mill's preventative maintenance program. Inadequate cooling of pellets can also lead to moisture migration, mold growth and finished feed bin corrosion problems. The temperature of adequately cooled pellets should be within 5 degrees Fahrenheit of the ambient temperature. Cooling problems are generally associated with bed depths that are too high or low, incorrect air balance (volume and velocity), and uneven bed depth.
Ensuring safe transport
The quality assurance program does not stop once the feed is manufactured. Proper delivery and storage of the feed on the farm is the final step to minimize mold growth. The feed delivery driver should routinely check that each compartment is empty and clean, with no residual feed build-up.
The driver should also make certain that the bulk bin lid is closed and locked prior to leaving the farm.
Moisture accumulation due to rain or snow in the finished feed bins can also lead to mold growth. The slide gate on the boot section of a farm bin is another location where water can enter the feed and cause mold growth. Finally, farmers and contract growers should routinely inspect and clean the bins on the farm to prevent mold growth due to the accumulation of finished feed on the side wall and cone of the bin.
Mycotoxin management programs
A safe, clean and well maintained feed mill does not "just happen;" it takes the efforts of management, operators and maintenance working together. Management has to set the example and standards for the employees, operators need to alert management about potential problems, and maintenance employees must routinely inspect, clean and maintain equipment to prevent mold growth.
A coordinated mycotoxin management program goes beyond sampling and rejection of out of specification ingredients. The feed mill manager must establish a comprehensive quality assurance program, train employees, and implement the program across for all feed manufacturing and delivery processes. Feed mill managers must also educate their customers and growers in order to help prevent mold growth and mycotoxin production in the bin on farm.
The production of safe feed for animals is the responsibility of all employees at the feed mill. Employees must understand the importance of their job in the production of safe feed and this must be reinforced by the management within the feed mill. The production of high-quality safe feed is a team effort, which requires the commitment of top management, the feed mill manager and employees.