 Batching and mixing are one of the most important processes during feed manufacturing and their main objective is to weigh each ingredient accurately and produce feed in which nutrients and medications are uniformly distributed. The mixing process is fairly simple and consists of transferring weighed ingredients to the mixer, mixing them for a designated dry cycle, apply liquids and then provide a sufficient wet cycle to ensure their distributions into a batch of feed. Although mixing is simple, there are many potential problems that can occur such as incorrect order of ingredient addition, overfilling if low density ingredients are used in some diets, build up on the ribbons or paddles, broken ribbons or leaking gates. These potential mixing problems can be identified and corrected with regular preventative maintenance and visual inspections. This feed bill managers and quality assurance supervisors should know the variation of nutrients in the finished feed produced in order to meet label guarantees and comply with FDA regulations if category 2 medicated feeds are being produced. In addition, animal feeds are intended to be fed as a sole source of nutrients and any nutrient deficiencies or toxicities caused by poor mixing can affect animal performance, health and egg production. Markers should be tested to evaluate mixer uniformity after installation, after corrective maintenance such as replacement ribbons and at least annually to determine optimum mixer uniformity. Mixer uniformity is used to measure the degree of dispersion of the ingredients in a batch of feed and it is estimated by the coefficient of variation of a specific nutrient or ingredient. Some of the most common markers used are chlorine from salt, trace minerals and synthetic amino acids. The desired markers should come from only one source, be approved for use in animal feeds, have a standard methodology of analysis and have an inclusion level less than 0.5%. Usually as mixing time increases, mixer uniformity increases. The first step to evaluate mixer uniformity is to label 10 sample bags from 1 to 10, verify the feed type, lot number, date and other relevant information to your facility. Representative samples should be taken directly from the mixer, surge hopper under the mixer from 10 pre-selected locations or during mixer discharge as feed moves from the mixer to the mash leg. Samples taken during discharge should be collected at evenly distributed intervals in order to sample the whole batch of feed. To analyze mixer uniformity using the Quantab Chloride Tie Trader Method you need a water heater with distilled water, a bottle of Quantab Strips, filter paper, a scale, labeled samples 1 through 10, labeled cups, a spoon and individual Quantab Strips. First you need to weigh a 10 gram sample from each bag into a cup. Then add 90 grams of hot distilled water to the cup using a 0.1 gram readability scale for both sample and water. The hot water helps to solubilize and extract the salt from the sample. The next step is to stir the mixture for 30 seconds and allow the mixture to rest for 60 seconds and then stir for another 30 seconds. After stirring, place a folded filter paper into the cup and then insert a Quantab strip with a range of 30 to 60 milligrams per liter into the liquid at the bottom of the filter paper. It is very important to use the same lot of Quantab Strips for all 10 samples you will analyze. The Quantab Chloride Tie Trader consists of a thin plastic strip laminated with a capillary column impregnated with silver nitrate and potassium dichromate, which together form silver dichromate. When the strip is placed in a chloride ion solution, the color of the column changes from reddish brown to a white yellowish color due to the reaction of the chloride ion with silver dichromate, which creates silver chloride. Once the reaction has finalized, the color on the top band of the chloride tie trader changes from yellow to black. The next step is to compare the Quantab strip reading to percent sodium chloride using the chart on the bottle. For example, if the reading was 4.6, the amount of salt in the sample is 0.036, then multiply that value by 10 to account for the dilution factor. This will be equal to 0.36 percent salt in the sample. Repeat the same procedure for the other nine samples. Once you have determined the salt content in each sample, you can compute a CV from the results of 10 samples within a batch to determine mixing uniformity. Using an Excel spreadsheet, you can calculate the average and standard deviation. The CV for each batch is calculated by dividing the standard deviation by the average value multiplied by 100. You can include batch, sample number, sample weight in grams, Quantab units, and percent sodium chloride. The next step of the assay is to interpret the results of the mixer uniformity tests and take corrective action if necessary. A percent CV of less than 10 percent is excellent and there's no corrective action needed. From 10 to 15 percent, it is good, and to make it better, the mixing time should be increased by 25 percent to 30 percent. From 15 to 20 percent CV, it's fair, and it can be corrected by increasing the mixing time by 50 percent, looking for worn equipment, overfilling, or sequence of ingredient addition. If it is greater than 20 percent, it is poor, possible combination of all of the above. Consult extension personnel or feed equipment manufacturers. Remember, if your mixer uniformity was poor or fair, you need to conduct the mixer uniformity assay again after the corrective action to ensure your mixer uniformity is good.