 The majority of feed ingredients used in poultry feeds require some type of grinding. Serial grains such as corn and wheat are ground at the feed mill, while other ingredients are received in a ground form. Grinding is the first stage in feed manufacturing prior to batching and mixing. Particle size reduction during grinding increases handling, reduces ingredient segregation after mixing, and increases the surface area of the feed particles, which improve steam penetration during conditioning and particle agglomeration during pelleting. However, excessively ground ingredients can increase grinding costs, lead to dust pollution, and moisture losses during grinding. Course particles reduce grinding costs, increase gizzard development, and reverse peristalsis, which can lead to better nutrient digestibility. Evaluating particle size is an important component of a feed manufacturing quality assurance program. Particle size analysis should be performed at least weekly, after preventative and or corrective maintenance, and when the characteristics of corn change, for example, when new crop corn with higher moisture content is received. The first step is to obtain a sample from a sampling port close to the hammer mill or roller mill. A good sampling spot is the transition between the grinding equipment and the ground corn elevator. The material is used to run the analysis of the following. The sample to be analyzed, a sample splitter with its cups, a scale with an accuracy of plus or minus 0.1 grams, a tray to weigh the sample, sieving agents such as silicon dioxide and the spoon, a brush, paper and pencil, a tray used as trash, and finally a road tap with its complete set of sieves. The next step is to divide the sample and weigh 100 grams using a scale with plus or minus 0.1 grams of accuracy. A 100 gram sample is recommended to avoid accumulation of more than 20 grams over any one sieve, which can prevent particles from moving to a lower sieve. Place the 100 gram sample into the tray. Now add 0.5 grams of sieving agent to prevent particle agglomeration, particularly in ingredients of feeds with the high fat content. After adding the sieving agent, mix the sample and the sieving agent gently to distribute the sieving agent homogeneously in the sample. Screen cleaners can also be used to ensure that every particle has the same chance to pass through the openings. A stack of sieves with different diameter openings is used to separate particles according to their size. The Tyler sieve series identifies sieves by the number of holes per inch, so a lower number equals to higher hole openings or less holes per square inch. The sieves can also be identified by size opening in millimeters or microns. You need to arrange the sieve stacks so the course's sieve is on top and the finest sieve is on the bottom. Remember, as the USA sieve number increases, the sieve opening becomes smaller. Place the stack of sieves in the ROTAP shaker, which mechanically produces a circular motion similar to hand sieving and a tapping mechanism which helps particles pass through the mesh screens until the particles reach a sieve small enough to pass. Adjust the time for 10 minutes. Once the ROTAP has stopped, remove the sieve stack from the shaker and proceed to weigh the amount of material in each sieve. Place the sieve with the retained material on the scale. Tear the scale to zero, and then thoroughly clean the sieve with a brush or using a vacuum. Do not wash the sieves as it will make the wire mesh rusty, narrowing the opening, making the results inaccurate and leading to an overestimation of the particle analysis. Weigh back the empty sieve and record the weight. The weight should be negative, which corresponds to the weight of the material in a particular sieve. Repeat the procedures for each of the sieves. This spreadsheet includes a variety of rows and columns which include materials used, date and initial weight, and if a sieving agent was used. The first column identifies the screen number. Second column refers to the diameter opening of the sieves and microns. Third column is the amount of feed or grain retained in each sieve. The percent column is used to create the histogram. And the percent less than column can be used when graphing using probability paper. The remaining columns are used for obtaining values that will be used in the formula to obtain particle size and standard deviation, and then surface area and particles per gram. Feed manufacturers and nutritionists are generally interested in the average particle size and the standard deviation. Data recorded should now be entered into the appropriate columns of a spreadsheet developed by Kansas State University. Now using the weight in each sieve, you can calculate the summation, the particle size and the standard deviation, as well as create a graph that shows the distribution of particle sizes around the sample that was evaluated based on the size of the sieves opening in the second column and the weight of each sieve in the third column. In this case, you can see that most particles have a size between 590 and 1190 microns. The recommended corn particle size in swine is around 600 microns in mashed diets and around 400 microns in pelleted diets. The optimum corn particle size for newly hatched chicks or pellets during the first two weeks should be around 850 microns, but can be increased during grower and finisher periods. Layers might benefit from even larger particles, but you should monitor feed segregation as excessive coarse particles can increase ingredient segregation in mashed diets.