A particle size test that is about 30 times faster than current methods, yes please! Most feed laboratory managers do not need to think long and hard about whether they would like a more convenient test for particle size in animal feed. In pursuit of this goal, Dr. Adam Fahrenholz at North Carolina State University has teamed up with analytical solution providers FOSS to look at how near infrared (NIR) instruments could take on the job.
A quick review of the current analysis method reveals why a faster analysis would be so welcome. Involving equipment such as sieves and sieve-shakers, the particle size test typically takes 15 minutes, plus five to ten minutes of preparation time and analysis time, not including the recording of time and date information. A single test can take a well-trained operator anywhere from 20 to 30 min depending on what they are testing for. At the same time, particle size is so important to the feed mill that multiple analysis may be required per day when setting up equipment, and often once per shift, or several times a week under normal operations.
Importance of particle size
One use is to gauge the performance of equipment. “If, for example, I have targeted a specific micron size, let’s say 700 microns, when I put new hammers and new screens on my hammer mill, I’m targeting these 700 microns based on screen size and hammer speed that I have chosen. So I know that my system is doing what it is supposed to do,” explains Fahrenholz. “By measuring the particle size continuously, I can evaluate when it’s time to change those wear components, or when to make a change because I start to receive a slightly different physical characteristic of grain that makes the particle size start to deviate from the target.”
Particle size is also important for the physical flow of the feed, especially for meal feeds. For instance, if the particle size is overly fine it can lead to problems in flow through feeders and out of bins. And perhaps most importantly, on the nutrition side, particle size affects feed conversion for both pigs and chickens either in terms of intake or digestion or both. For poultry, some coarse particles in the diet are necessary for gizzard health “At the end of the day it all comes down to what gives us the most efficient pounds of feed per pound of gain of that species,” concludes Fahrenholz. Yet another factor for feed millers to consider is the variability of raw material, for instance when a mill switches over from so-called old crop corn harvested the previous year to the new crop corn that will grind differently.
Tracking particle size
The bigger the operation, the bigger the potential impact of variations in particle size becomes. Some manufacturing facilities are turning out huge amounts of feed, perhaps around 20 to 25,000 tons of feed per week. Running 24/7, the mill is getting more mileage than a yellow cab and wear parts such as screens and hammers need replacement every few weeks.
With the current method, if the particle size starts to drift out of spec, a lot of feed can go through before a control test shows the trend. The feed is still usable and no animals are going to starve, but can it live up to the all-important feed conversion promised to customers? In this situation, the feed mill manager has to decide whether to live with the trend or change screens and hammers earlier than expected. “If you had the ability to generate ten particle size samples a day, anyone could easily run them and track it, and when the control parameter drops below a certain point, you would know it’s time to make a change,” says Fahrenholz. “This would bring value not only to the animal, but also to the feed mill bottom line.”