Sample representativeness: Key considerations during sampling
Sampling is critical for ensuring good animal performance, food safety, and compliance with federal regulations.
By Wilmer Pacheco, Charles Stark, and Adam Fahrenholz
Sampling incoming ingredients, mash feed, pelleted feed, and finished feed at the feeder level is critical for ensuring good animal performance, food safety, and compliance with federal regulations.In this article, we will discuss the importance of obtaining representative samples during the journey of feed from ingredient receiving at the feed mill until complete feed reaches the feeder.
Ingredient receiving
Representative sampling of incoming ingredients is crucial for assessing their quality and safety. It is essential to obtain 10 evenly spaced random samples from different parts of the bulk carrier. These 10 samples will provide a representative sample of the entire load. In addition, sampling at least 10 bags of bagged feed ingredients will ensure the obtention of a representative sample of the entire lot. The sample size depends on several factors such as lot size (e.g., size of the truck, rail car, or number of bags on a pallet). Other considerations include variability of ingredients (i.e., more variable ingredients require a higher sampling frequency), laboratory capacity to process samples, analytical cost, and ingredient value. Collecting samples to evaluate mycotoxin contamination in incoming ingredients is important for compliance with the Food Safety Modernization Act (FSMA). Since mycotoxins are not evenly distributed in feed ingredients, collecting a sample from a single location can lead to inaccurate results.
Grinding
Particle size of ground cereal grains influences animal performance. Therefore, it is important to collect a representative sample after grinding. Samples can be collected from the transition between the transfer conveyor at the bottom of the hammermill or roller mill and the ground grain elevator. Samples should be split two or three times using a splitter to obtain 100 +/- 5 grams for particle size analysis. It is not recommended to take a sample from the top of a bag as small particles can segregate to the bottom, which can lead to an overestimation of the average particle size.
Batching and mixing
Batching and mixing processes are the core of any feed manufacturing operation, requiring precise weighing of ingredients and uniform mixing for optimal results. Mash feeds should undergo annual sampling to assess mixer uniformity. Collect 10 samples from various points within the mixer (adhering to safety protocols such as lockout/tagout procedures), surge hopper, bottom of drag conveyor, or transition between the drag conveyor and mash elevator. When collecting samples from the bottom of the drag conveyor or before the mash elevator transition, it is essential to time how long it takes for the entire batch to pass the sampling port. After calculating batch transfer time, the personnel responsible for mash sample collection can discard the initial and final portions. Samples should only be collected from the middle of the batch. For example, if the batch transfer time is 300 seconds, removing the initial and final 15 seconds entails collecting samples at intervals of 27 seconds, starting at 42 seconds, and ending at 285 seconds. Correct calculations will ensure 10 representative samples are collected from the entire batch. Feed mills may employ a self-administered analytical method, such as the Quantab® chloride titrator, to analyze their mixer uniformity, while others may send samples to a lab in order to measure synthetic amino acids (e.g., lysine, methionine, or threonine), micro minerals (e.g., zinc and manganese) or micro-tracers. However, if your feed mill uses a micro-tracer, ensure samples are collected before the feed batch reaches a magnet. This will prevent micro-tracers from being removed by the magnet, which could affect accuracy of the mixer uniformity test results.
Conditioning and pelleting
It is common practice to collect conditioned mash samples to determine moisture added during conditioning and steam quality. However, keep in mind that mash leaving the conditioner is both moist and hot. To accurately assess moisture content of conditioned mash samples, samples should be promptly sealed in a small container after collection to prevent moisture loss. Afterwards, samples should be cooled (e.g., samples can be placed in a refrigerator or left at ambient temperature for 30 to 45 minutes) to facilitate steam condensation on the feed particles. Once cooled, samples should be homogenized before measuring their moisture content. When we visit feed mills, it is commonly seen that personnel underestimate the moisture content of conditioned mash, typically due to incorrect sampling (e.g., hot samples exposed to the environment before sealing) or improper handling before analysis. For example, if the sample is analyzed while it is still warm or hot, moisture levels may continue to decrease because of moisture being released into the environment.
Cooling and crumbling
As a component of their quality control program, several companies gather samples of pelleted feed at various stages: post-cooler, after post-pellet liquid application, prior to storage in the finished feed silo, or during load out. This is performed to assess the percentage of fines or to conduct an analysis of pellet quality. During sample collection, it is crucial to gather information about factors that could impact pellet quality such as conditioning temperature, production rate, percentage of fat added in the mixer, and other relevant variables for the operation. Data collected can be utilized to generate run charts to assess the impact of various factors on pellet quality of finished feeds. Sampling for crumble quality is equally significant, as it directly influences performance during the crucial pre-starter and starter phases of broilers, turkey poults, and pullets. For optimal assessment, it is advisable to gather individual samples from each side of the crumbler and compare the quality of the crumbles from each side to gain insights into the alignment of the crumble rolls.
Farm sampling
Obtaining samples at the feeder level is important to assess physical and nutritional quality of feed directly in front of the animals. Remember that feed is typically fed as the only source of nutrients during animal production; therefore, it must contain all the necessary nutrients for growth and production. It is necessary to collect multiple feed samples to account for potential segregation during delivery or distribution within the production barn. Additionally, it is not advisable to collect samples directly from the feeder as animals typically prefer pellets, potentially leading to an underestimation of feed quality in front of the animals. Instead, approximately two pounds of feed can be collected from the auger at various points along the feeding line (i.e., beginning, middle, and end). This method could provide a more accurate measurement of both the physical and nutritional quality of the feed and to evaluate if segregation is occurring.
Remember, if the samples are not representative of the whole lot of ingredients, the batch of feed, or finished product, quality assurance results could be meaningless and can lead to poor management decisions.
