KANSAS CITY, MISSOURI, US — Quality assurance (QA) in the feed mill can be the dictating factor of success in both commercial and integrated feed mills. Ingredient and finished feed quality can be described by both physical and analytical characteristics that can influence animal performance, customer satisfaction, and have regulatory implications. 

 To establish a QA program that will best meet the needs of the feed mill, standards that align with the facility's objectives should be established. These standards may include but are not limited to measures in areas such as receiving, grinding, mixing, and batching, pelleting, nutrient analysis, and facility and personnel biosecurity. 

Purchasing and receiving ingredients

Typical ingredients received by the feed mill include grain and byproducts in bulk and micronutrients or other ingredients in bags or totes. It is important for individual feed mills to have defined criteria for accepting and rejecting ingredients as they are received. Standards for receiving ingredients may be the observation of manufacturing and expiration date, torn or damaged packaging, remnants of infestation from bugs or rodents, and in some cases analytical nutrient analysis.

Determining the quality of ingredients at receiving is critical for accurate formulation and strategic feeding. A representative ingredient sample is important to establish accurate assessment of quality and nutrient profiles for each ingredient. There are numerous factors that influence the quality of the sample, including ingredient characteristics, sample technique, sample tools, and the point in time the sample was taken. Once the samples are collected, the use of quick tests, such as NIR and mycotoxin testing, allows for fast, informed decision-making and eventually can lead to decreased commercial laboratory evaluation costs. 

Specifically, testing of all grains for animal feed should follow the quality measures listed in the Grain Inspection Handbook Book II Grain Grading Procedures. It outlines the procedures for grading grain in accordance with the Official United States Standards for Grain, explaining how to determine if standards have been met in accordance with the United States Grain Standards Act. Grain quality is typically determined by physical observations like damaged kernels, odor, bug infestation, and foreign material, and analytical observations like moisture, test weight, and mycotoxin concentration. 

The determination of the moisture content of grain is important for making decisions pertaining to storage, shrinkage, and other feed milling processes. Moisture analysis of whole grain ingredients should be done for every incoming load due to the effects that added moisture can have throughout the feed manufacturing process. Options for rapid analysis of moisture include using a Dickey-John moisture analyzer or near-infrared spectrometry (NIRS). Test weight per bushel can be determined using an electronic apparatus outlined by the Approved Equipment Handbook by the USDA Federal Grain Inspection Service. 

Mycotoxins are one of the major quality concerns for cereal grains. Mycotoxins can be produced in the field or in storage. Field toxins include deoxynivalenol (vomitoxin), zearalenone, and fumonisin and storage toxins include aflatoxin and ochratoxin. To determine the risk of mycotoxin contamination from grains, weekly reports are available to assess the risk of mycotoxin contamination in grains from specific areas that can help determine how many loads to sample. 

Lateral flow test strips or enzyme-linked immunoassay (ELISA) kits are commercially available and can be used as a single mycotoxin test to determine the toxin level present in grains and byproduct ingredients. However, it is important to note that each type of mycotoxin requires a specific test. The FDA has published guidance levels for vomitoxin and fumonisin and has published regulations and compliance policy for aflatoxin. 

Particle size reduction of cereal grains

Cereal grains are ground to improve mixability and bulk density and increase nutrient digestibility by breaking the hard, protective outer layer of the grain. Concentrated nutrients in the endosperm and germ become more available as the surface area to volume ratio increases, allowing more access for digestive enzymes. 

Factors that influence subsequent particle size of grains include grain growing conditions, grain moisture, mill type and settings, and mill maintenance. Therefore, measuring particle size becomes a critical step in quality feed manufacturing.

There are many factors that influence subsequent particle size and manipulation of any can produce a variety of particle sizes. For a complete particle size analysis both geometric mean diameter dgw and geometric standard deviation Sgw must be evaluated. Using the same particle size testing method (3-sieve or 13-sieve stack) is important to remain consistent to compare results to previous particle sizes and observe changes when manipulating equipment and equipment wear. 

For a detailed description of testing procedures, see “MF3342 Evaluating Particle Size of Feedstuffs — Kansas State University.”

Batching and mixing

Nutritionists formulate diets based on the assumption that the animal will receive all the nutrients needed for maintenance and growth each time they go to the feeder. Batching and mixing are the two major factors that influence ingredient/nutrient addition and distribution in feed. How ingredients are stored after receiving, order of ingredient addition to mixer, scale accuracy, ingredient characteristics, mixer type, and mixing time all play an integral role in final feed quality. 

Collecting system data over time can be a management tool used to create change and maintain processes and equipment. Using statistical process control (SPC) analysis can help with the predictability of the batching system. 

For precision formulation to be successful, a uniform mix must be determined by the coefficient of variation (CV). Procedures for testing mixer uniformity can be found in “MF3393 Testing Mixer Performance — Kansas State University.” 

A mixer uniformity test is often done by using a single source tracer (i.e. salt, trace minerals, or iron filings) as the indicator. Ten samples should be pulled in order from mixer discharge or sack off with a probe and the tracer analyzed to be tested for uniformity. The CV can be calculated by CV% = (standard deviation/mean) × 100%. Any changes in mixing should be validated by mixer uniformity. Mixer uniformity CVs should be done annually, if not bi-annually, for validation or when there are major changes in ingredient characteristics or equipment. The feed industry standard is to achieve a CV of less than 10%. 

If results are between 10% and 15%, it is considered a good mix, and mixing time should be increased by approximately 25%. With results of 15% to 20%, mixer time should be increased by 50%, and mixer wear and ingredient propriety should be addressed. Any results greater than 20% are considered poor and should be evaluated.

Pelleting

Pelleting animal feed provides many benefits from improved palatability and flowability to decreased feed wastage, reduced ingredient segregation, and destruction of pathogens. When quality is maintained, pelleting feed may show benefits with improved average daily gain and feed efficiency. 

There are numerous factors that impact the pelleting process, including diet formulation, pelleting conditions, and specific pellet mill components. There are also many processing parameters that influence the pelleting process and pellet quality. 

While there is an added cost and processing step to pelleting diets, the payout can be seen in increased bulk density and handling characteristics and animal performance. Factors such as formulation, equipment design, and manufacturing parameters not only determine pellet quality but also pellet mill production rate and energy consumption. Factors influencing the percentage of fines at the feeder include ingredient characteristics, the conditioning process, pellet mill configuration, pellet cooling, and transportation. After cooling, pellets are run through several feed lines and transported to farm sites that can be an abrasive process that influences what pellets look like at the mill compared to the feeder. 

To determine pellet quality at the feeder, the combination of pellet fines at the feeder and pellet durability index (PDI) at the feed mill are used. Percent fines are determined by the number of fines sifted from pellets. To determine PDI, a tumble box or a pellet durability tester from the Holmen series may be used. 

Comparing samples from the farm and feed mill can determine the adjustments needed. These adjustments include modifying the standard method or the amount of time pellets need to be in the chamber of the Holmen pellet tester. A detailed procedure is outlined in “MF3228 Evaluating Pellet Quality — Kansas State University.”

Finished feed

The transportation and unloading process of finished feed can be time consuming and challenging to maintain feed quality. Efforts should be made to minimize delivery mistakes through sampling, documentation, and attention to detail. 

It is important to make sure bagged feed is sacked and labeled appropriately, and bulk feed is delivered to the correct location at the correct time. This ensures the outline nutrition program is followed and that feed and resources are being optimized. Also, collecting a representative finished feed sample is important for finished evaluation. At a minimum, it is recommended to sample each formula once per week or 1 sample per 100 tons of production, whichever will provide more samples (Jones, 2006). 

Finished feed samples should be retained as composites for six months or one year for medicated feeds. New VFDs for category II medicated feed must be sampled and assayed three times in the first year and annually after that. Records must be kept for one year for finished feed and two years for VFD’s. Samples should be evaluated for texture, pellet quality, color, and odor. Anything unusual should be recorded and addressed. The nutrient composition can be evaluated using NIRS or a commercial laboratory. The NIRS technology can serve as an internal assessment before delivery or for problems with ingredients or finished feed. 

Establishing accurate NIRS calibrations is imperative for predictability. This technology can determine the nutrient content of ingredients or complete feed, which is helpful in determining ingredient quality. Advancements have been made with NIRS technology in feed mills to include in-line analyzers, providing results as ingredients pass along a sensor allowing for continuous monitoring and segregation based on nutrient value. 

Biosecurity

Biosecurity practices are implemented to minimize the risk of introducing biological hazards into the feed mill that could compromise animal health status and cause significant economic loss. Therefore, there is increasing interest in opportunities to reduce risk through the development and implementation of biosecurity plans for the feed mill. A biosecurity plan requires the identification and evaluation of hazards and the implementation of prevention and mitigation strategies. Implementing a plan to prevent or mitigate biological hazards in a feed mill is challenging because of differences in facility design, manufacturing operations, and significant risk factors among feed mills. The first step toward minimizing risk is to develop a feed mill biosecurity plan. 

While the success of biosecurity practices will never be known, the cost of an outbreak far outweighs that of prevention. Key feed safety and biosecurity resources can be found at the following website: https://www.asi.k-state.edu/research/feedsafetyresources/.

Quality assurance programs will vary depending on the objectives of the feed mill and the types of species being fed. It is important for feed mills to determine their most important quality assurance parameters to meet the mills objectives. Clearly defining quality assurance goals and providing resources to achieve these goals is key to a successful quality program.