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Waking up to the fundamentals of pellet quality -
Dr Keith Benke gives the Anitox Breakfast Lecture at the IPPE in Atlanta “Mixing and pelleting are the most expensive operations you’ll find in a feedmill” says Dr Keith Benke (consultant, formerly of Kansas State University’ Grain Science and Industry Department in the US) to delegates invited to the Anitox Breakfast Lectures on the opening morning of the 2015 IPPE Exhibition in Atlanta, Georgia in January.
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r Benke was one of two specialist invited to address nutrition and health issues in poultry and pigs. Mixing is not expensive but if not done right it will have an adverse impact on chickens and pig production, he says. “The objective of mixing is to achieve a uniform mixture of both solid and liquid ingredients in a formula, without nutrient destruction and in the minimum amount of time.” Most feed manufacturers will be following the recommendation of the mixer manufacturer as to total time from last ingredient added to the drop of the mixed batch. “How do you know what is long enough?” he says he has frequently asked feed manufacturers. “Many says they ask the mixer manufacturer who will say just mix for two minutes!” However, mixing dry ingredinets first and then adding wet ones is the correct approach. Don’t add wet ingredients too early, he advises. “If we don’t mix the dry ingredients well before adding liquids you take the risk of slowing the mixing action – let’s use at least a 20-30 second period before wet additives are added.”
The importance of mixing can’t be overstated
Using tracers such as synthetic methionine and Lysine is often a good choice when checking the mixing accuracy. Co-efficient variation should be less than 10 percent on whatever you’re looking at, he explains when reviewing past results of trial work undertaken by Kansas State University for industry. “How well does the broiler industry do? Looking at methionine and Lysine as tracers, about 50 percent of industry within the 10 percent CV threshold while 30 percent was between 10-20 percent CV. The balance – about 25 percent were over the 20 percent CV mark. That means that half the mixers profiled were in the right region, under the defacto threshold. The 25 percent that were over the 20 percent threshold represents a lot of tonnage and in turn 46 | Milling and Grain
means that farmers have a problem. “There are mixers out there that are not doing a good job.” “I can guarantee that if your mixing is greater than 20 percent coefficient variation, your effecting animal performance. There are animal out there not getting the nutrient mix they need because the right job has not been achieved in the feedmill.” Concluding the section of his presentation on mixing he added ‘salt’ to the list of useful tracers.
The impact of poor mixing
Dr Benke explained that while a 180lb (80kg) pig may not exhibit the impact of nutrient shortfall in in one day - provided the pig gets a balance of nutrients over a period – the same cannot be said of poultry. They exhibit no differences that can be traced back to poor mixing in the mill. However, the same cannot be said of poultry. “The pig ate three to four pounds (1.5-2kg) of feed per day while the chiken on a starter diet eats only 100 grams.” Meal size is very important when reviewing the need accuracy at the mixer, he says. His comments are based on work done where mixing times and CVs were compared. “What does this mean in an actual mill that has, for example, a four tonne mixer? “The 4000kg of mixed feed, contains four million grams in each batch. For a starter diet for a day old chick the ration is just 10g. That means there are 400,000 one-day rations in one batch for one day rations for a starter feed for chickens? “What is the chances of those one-day 10 gram rations being exactly right as the nutritionist predicted them to be? Probably not too much. As you go through starter, grower to finisher and withdrawal feeds, the meal size gets bigger and the pressure on the mixer uniformity probably is a little less as the meal sizer become larger, he says. “But you can’t cut the mixing time down! That uniform random mixer is very important even at these latter stages.” The mixer needs to be clean – and cleaned safely – otherwise they build up layers of materials that will ultimately alter the mixing profile. Dr Benke warned that cleaning mixers is a dangerous task. “While an operator may have ‘locked out’ the mixer, but has he not overlooked the fact that the discharge doors are controlled by air cylinders and are on another circuit?” By entering from below he is at risk of injury or worse if he has not done both, he adds..