May 13, 2015

13/05/2015: Waking up to the fundamentals of pellet quality

Dr Keith Benke gives the Anitox Breakfast Lecture at the IPPE in Atlanta

First published in Milling and Grain, March 2015

“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.

Dr Benke was one of two specialist invited to address nutrition and health issues in poultry and pigs.
Image: nav in atl
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 say 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 de facto threshold. The 25 percent that were over the 20 percent threshold represents a lot of tonnage and in turn 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.
Image: Nick Saltmarsh
The impact of poor mixing
Dr Benke explained that 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. 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 chicken 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, has he 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.

“There are lots of mixers in the pig and poultry industries that are clogged with fat on their mixer spokes.
Image: Barry Skeates
“Mixing for five minutes in an un-cleaned mixer will still leave the mixed feed in the higher CV range. Whereas, with a clean mixer its almost down to the 10 percent CV threshold after five minutes and within the range at six minutes,” he says.
He concluded this section of his presentation saying uniformity can be measured using chloride ion, sodium ion, dyed iron particles, elemental ayalysis, antibiotics/drugs and crystalline amino acids.

“All of these are useful methods,” he added.

The impact of fines
There are food safety issues involved with too many fines in pelleted feeds, Dr Benke went on to say.

“And if we can’t do better than 30-40 percent pellets in the feed at the farm, we might as well turn the pellet mill off,” he adds.

With 25 percent pellets and 75 percent fines in a finished feed at the farm is a problem when 60 percent of what chickens consume is pellets. Almost all the chickens ignored the fines completely.

“Broilers are very selective eaters and will select pellets over fines. We all know this,” he says.

The ratio of pellets to fines impacts performance. Eating pellets means birds will eat and then sit, not burning energy. Chickens forced to eat fines utilize more energy doing so and partition their energy differently.

Dr Benke says the causes of fines occurring in feed pellets is 40 percent due to the formulation and just 20 percent due to pelleting.

“We can’t formulate for pellet quality successfully. The ingredients that go into a feed have a major impact on pellet quality.”

Fineness of grind – generally speaking the finer the better the quality – the better the pellet as finer particles have more surface area to absorb steam dueing the conditioning process.

“We can’t solve a pellet -uality issue by just looking at the pellet mill.

Conditioning is much more important than the die. And conditioning is anything we do to the feed after it leaves the mixer and before it gets to the pellet mill. Usually that includes just steam conditioning,” he says.

Long-term, or two-pass conditioners with some having up to four-pass conditioners, creates longer conditioning times.

“Thirty to thirty-five seconds is probably enough if we get enough steam and moisture in. In my opinion pellet quality is establish in the conditioner and not in the pellet die.

“Therefore we want to use the thinnest die we can get away with as it will impact throughput. We need to maximise conditioning.

“By conditioning we are activating the starch on the surface of particles. We are cooking, gelatinising the starch, on the surface of the particle. That doesn't affect the animal at all. We rely on cooked starch to hold the particles together. If we don’t, we get weak bonds and pellets will break apart and that’s how we end up with only 30-40 percent pellets in the feed out in the field.”

In-line moisture control

What happens to pellet quality if we precisely control moisture? He asks.

A trail with a moisture meter in the mixer allowed the operator to calculate how much moisture was needed to bring the feed up to what was required.

The device was extremely accurate, says Dr Benke, and worked very nicely with no recording our by more than 0.2 percent.

“If a pellet mills sees the same moisture in the feed coming through hour-after-hour, then a lot of the variability in pellet quality simply goes away,” he says.
Image: Alternative Heat
Energy at the die
The only source of heat at the die is friction. Moisture is acting as a lubricant with the load on the motor going down.

“There’s still a huge amount of pressure in there – up to 20,000lb/square inch - forming the pellets. If we can cut down on that frictional heat, which is electrical energy being converted into heat, will not mean the pellet quality is going down.
If we can cut down on energy we can save rather than just paying to convert electrical energy to friction at our expense.”

He says there is still controversy over adding addition water at the feedmill that millers see as simply hauling water from the mill to the farm with its implications for additional costs.

Dr Benke says there is still a huge amount of resistance to adding water at the feedmill as its claimed that for every percentage of water added there is a reduction in animal performance, or feed conversion, of two points.

“However, if I can improve pellet quality and keep the pellets between 70-80 percent of the feed and keep it there all the way to the bird in the end of the shed, I can match that with a five percent improvement in feed conversion – just through pellet quality.

“Besides we can get most of that moisture out through the cooling process these days. But we need to understand cooling much better than we do and the impact it has on pellet quality. Coolers need to be run much better.”

In conclusion, Dr Benke summarised several key points he had highlighted during the breakfast meeting:

  • Pellet quality is critical to animal performance
  • If millers do a good job they can improve animal performance
  • Nutrient uniformity is critical especial in the starter diets
  • Meal size is important
  • Use water intelligently. Water is critical to pellet quality and should be managed as an ingredient
  • Is it necessary to spend money to make money? Yes it is
“The industry over many years has gone too far in the direction of saving money, trying to limit costs, instead of spending money wisely and particularly on good feed manufacturing technology.”

Read the magazine HERE.

The Global Miller
This blog is maintained by The Global Miller staff and is supported by the magazine GFMT
which is published by Perendale Publishers Limited.

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