In our previous article, the importance of testing feed mixing uniformity was introduced and the reader was taken through the test procedure, from sampling the feed all the way to interpreting the results. If the feed mixing process is not monitored, measured, and evaluated correctly, bird performance and the return on investment of the feeding practices may be substantially compromised. After recognizing the importance of the feed mixing uniformity test, the following questions come to mind. What should be done if the test results are not satisfactory? What actions should be taken to correct the feed uniformity issue? Answers to these questions and more will be explored in this article.
Feed additives such as vitamin premix, synthetic amino acids, and supplements are provided as a powder. There is a science behind powder technology and it is important to understand the behavior of powder in a mixture to optimize feed mixture uniformity. For example, segregation of a powder blend can compromise mixture uniformity if proper corrective actions are not in place. Powder technology plays such an important role in feed and pharmaceutical manufacturing that numerous scientific journals such as Powder Technology Journal publish the science behind this technology! If you are interested in this topic, you may consider reading more articles in the respective scientific journals to learn the fundamentals of mixing technologies.
Corrective actions for improper mixing uniformity
The corrective actions should be planned based on the factors affecting the mixing uniformity. Several factors, such as mixing time, mixer type, mixer loading, ingredient quality, mixer maintenance, and the sequence of ingredient addition, can affect the uniformity of the mix. Common corrective actions for mixing uniformity issues include increasing the mixing time, looking for worn equipment, mixer loading, and considering the sequence of ingredient addition.
Weighing process
Always try to monitor, measure, and analyze the weighing process to optimize feed mixing uniformity. Weighing accuracy can be compromised due to personnel factors, equipment calibration errors, and ingredient dry matter, which can negatively affect the feed mix uniformity. To minimize the personnel effect, try to make one person responsible for the weighing process and calibration checking. Ingredient moisture content can vary from batch to batch due to the origin of ingredients and transportation conditions, which can subsequently affect dry matter content. Thus, try to measure the moisture content and adjust the ingredient weight before weighing.
Mixing time
Mixing time is the duration for which the ingredients are blended together in the mixer. A proper mixing time depends upon the mixer type, manufacturer’s guidelines and ingredients. Different mixers have different mixing mechanisms and can handle different types of ingredients. Vertical mixers have two mixing zones (one at the top and one at the bottom of the center screw). In contrast, twin ribbon/paddle mixers create multiple mixing zones from the opposing direction of the ribbons as they rotate. As a result, vertical mixers take a longer mixing time than horizontal mixers to achieve comparable outcomes. It is recommended to allocate at least 15 minutes for mixing in a vertical mixer, 7 minutes for a horizontal paddle mixer, and 4 minutes for a horizontal ribbon mixer. In addition, a proper mixing time depends on the ingredient particle size. A batch of feed consisting of ingredients with consistent particle size requires less mixing time than a batch with inconsistent particle size. Remember that if the mixing time is too short, the ingredients may not be mixed thoroughly, resulting in poor mixing uniformity. On the other hand, if the mixing time is too long, it can cause over-mixing and result in a loss of ingredient quality.
Ingredient order
The order in which ingredients are added to the mixer can also affect uniformity. Optimal results are obtained by initially loading the mixer with a portion of the major ingredients (grains, soybean meal, or other energy and protein sources), followed by the minor ingredients and additives (vitamins, minerals, synthetic amino acids, and other additives), and finally, the remaining portion of the major ingredients. It is essential to add liquids (such as oil) only after thoroughly mixing all the dry ingredients. This can help ensure that all ingredients are evenly distributed and mixed thoroughly.
Mixer loading
Overloading or underloading the mixer can also affect feed mixing uniformity. Overloading the mixer can result in uneven mixing due to the creation of dead spots above the top of the ribbons/paddles and insufficient space for ingredients to move around. Underloading can lead to overmixing and the loss of ingredient quality. An optimal level of loading also depends on the mixer type. Horizontal mixer designs are constantly evolving and improving. In recent years, the twin-shaft ribbon/paddle combination has become the preferred choice, replacing the traditional single-shaft double ribbon used in many feed mills. The twin shaft design offers several advantages, including a shorter mixing cycle due to the multi-directional flow of ingredients in the mixing zone and the ability to handle a greater range of batch sizes. When using twin ribbon/single shaft mixers, keeping them at least 50 percent full during operation is recommended. However, twin-shaft ribbon/paddle mixers can operate effectively at just 25 percent of their rated capacity without compromising the uniformity of the feed mixture.
Ingredient quality
The quality of the ingredients used in feed mixing can also affect uniformity. Ingredients that vary in size, electrostatic charge, shape, or density can result in uneven mixing. One of the most important analyses is checking the ingredient moisture content, which can vary from batch to batch. The moisture content of the ingredients can affect mixing uniformity, as ingredients with different moisture levels can clump together and not mix properly.
Mixer maintenance
The condition of the mixer can also affect feed mixing uniformity. Worn or damaged parts can compromise the mixing process and lead to uneven mixing. Regular maintenance, including cleaning, adjustment of mixer ribbons to reduce the space between the ribbons and the mixer shell, and replacing worn parts, can help ensure that the mixer is functioning properly and producing uniform mixtures.
In summary, feed mixing uniformity can be affected by several factors, including mixing time, mixer type, mixer loading, ingredient quality, mixer maintenance, and ingredient order. Understanding these factors and implementing best practices can help ensure that feed mixing is consistent and uniform, resulting in optimal animal nutrition and health.
References
Mavromichalis, I. 2014. Mixing uniformity affects piglet and broiler performance. Feed Strategy digital magazine. (Link)
Purkhiser, E. D. and P. D. Bloome. 1984. Calibrating Meter-Type Feed Mills. Pork Industry Handbook. (Link)
Stark, Ch., and Saensukjaroenphon M. 2017. Testing Mixer Performance. Kansas State University. (Link)
