Egg Industry Articles

Uzelac Rotary Drying Systems to Process Layer Manure


Application of Uzelac Manure Drying Systems.


Uzelac Industries based in Greendale, WI. has developed considerable expertise in the design and installation of rotary drum dryers capable of reducing the moisture content of manure from high-rise houses with 65 percent water or belt systems with 45 percent water down to 15 percent. Manure handling and drying installations convert a waste product into a valuable pathogen-free fertilizer in a commercially acceptable form for domestic and institutional applications.


Direct application of raw manure to farmland will be subject to increasing restriction as nitrogen percolating through soil contaminates ground water and hence wells. Runoff entering streams and waterways will come under heightened scrutiny from state and federal regulators.

 A Uzelac rotary dryer installations reduces odor, obviating complaints and lawsuits and when used with belt manure collection, effectively eliminates fly problems without expenditure on insecticides. In the future environmental regulations may necessitate on-farm or remote processing of manure before application.


A typical Uzelac on-farm or remote installation comprises:-

  • Hoppers to accumulate raw material conveyed from houses or delivered from farms
  • A mixer to ensure that raw material is uniform in composition before processing
  • An air-heater assembly to fire the rotary drum dryer configured to the volume of input
  • A product collector to receive processed, dried material
  • A dust cyclone to limit air contamination
  • An optional pellet mill and pellet cooler to convert processed material into a saleable form
  • Packaging systems for either pelleted or granular products or a storage and delivery system for bulk product


Current Uzelac customers in the U.S. poultry industry include Herbruck’s Poultry Ranch, Giroux’s Poultry Farm, Michael Foods, Foster Farms and Tyson Foods among others.


Financial Evaluation of Uzelac Manure Drying Installations

Calculating the return from an investment in a manure drying installation is dependent on a number of factors including:-

  • Housing system such as high-rise, belt battery or aviary that will influence the moisture content of raw manure.
  • Prevailing power, gas and labor costs.
  • Single or two-shift operation to process manure from a complex or combination of smaller operations.
  • Seasonal climatic conditions with hot weather increasing water consumption of a flock, leading to manure with a higher moisture content
  • Size of supply flock influencing initial capital cost and utilization. Some installations are sited remotely to receive manure from a number of farms or complexes.
  • Form of product sold, whether bulk or bagged, granular or pelleted, will determine unit revenue.
  • State or local grants to offset capital cost.
  • Prevailing interest rates.


In order to calculate the return on investment from a manure-drying installation the following boiler-plate examples are provided. The first model assumes single shift operation, 40 hours/week; processing manure from one million hens in aviaries. The format allows insertion of specific values relating to a complex:- 

Capital cost of a Uzelac manure drying installation.

Buildings and installations


Mechanical equipment


Total Capital cost


Annual Fixed Cost of Operation :

Depreciation, Buildings @ 7% pa

$ 74,200

Depreciation, Equipment @ 15% pa

$ 441,750

Interest on capital @ 3% pa

$ 120,150

Overhead provision

$ 10,000

Annual Fixed Cost

$ 646,100

Annual Variable Cost of Single-shift Operation


$ 150,000

Maintenance provision

$ 50,000

Power Estimate

$ 250,000

Annual Variable Cost

$ 450,000

Annual Cost of Operation



In assessing the return on investment it is assumed that 1,000,000 hens in aviary houses produce 35,000 tons raw manure each year with 45 percent moisture content dried to 15 percent resulting in 24,500 tons of saleable product.


Revenue from dry product @ $145 per ton


Less value of wet manure @ $10 per ton

$ 350,000

Differential in revenue

$ 3,202,500

Add saving on fly and rodent control

$ 10,000

Annual Revenue

$ 3,212,500

Less Annual Fixed and Variable Costs

$ 1,096,100

Annual Contribution

$ 2,116,400


Discounted Cash Flow Calculation

In order to evaluate the capital cost of the manure drying installation the annual contribution over a five-year period would be:-


Year 1 2 3 4 5

5% discount factor

0.95 0.91 0.86 0.82 0.78

Annual Revenue ($ mil.)

2.01 1.93 1.82 1.74 1.65


Net Present value over 5 years attains $9.15 million


This exceeds Present Value applying 5% annual discount factor


Discounted payback of 25 months

In evaluating the effect of selling price as the major variable influencing ROI a series of DCF calculations were performed yielding the following results:-


Selling Price per ton Net present Value of Investment over 5 years


$ 75 $1.74 million
$ 85 $2.79 million
$105 $4.91 million
$125 $7.03 million
$145 $9.15 million


The return on investment is extremely sensitive to unit selling price. At $105 per ton the project would require 47 months to achieve a breakeven net present value of $4 million, corresponding to the original capital investment.


In demonstrating the influence of volume and price on the return on investment the manure-drying installation was evaluated with the theoretical output of 2 million hens, operating the Uzelac plant on a double-shift schedule 80 hours per week, corresponding to five, 16-hour working days. In this approach in the interests of simplicity, fixed costs of $646,100 would remain unaltered but variable costs would double to $900,000.


Annual Cost of Operation $1,546,100


In assessing the return on investment it is assumed that 2,000,000 hens produce

70,000 tons wet manure each year at 45 percent moisture content dried to 15 percent resulting in

49,000 tons of saleable product.

Revenue from dry product @ $145 per ton $7,105,000
Less value of wet manure @ $10 per ton $ 700,000
Differential in revenue $ 6,405,000
Add saving on fly and rodent control $ 20,000
Annual Revenue $ 6,425,000
Less Annual Fixed and Variable Costs $ 1,546,100
Annual Contribution $ 4,878,900

Discounted Cash Flow Calculation


In order to evaluate the capital cost of the manure drying installation the annual contribution over a five-year period would be:-

Year 1 2 3 4 5
5% discount 0.95 0.91 0.86 0.82 0.78
Annual Revenue ($ mil) 4.63 4.44 4.20 4.00 3.81

Net Present value over 5 years attains $21.08 million


Exceeds Present Value by a factor of 5 applying a 5% annual discount factor

Discounted payback period of 10 months

In evaluating the effect of selling price as the major variable influencing return, a series of DCF calculations were performed yielding the following results:-

Selling Price per ton Net present Value of Investment over 5 years

$ 75 $ 6.27 million
$ 85 $ 8.37 million
$105 $12.61 million
$125 $16.84 million
$145 $21.08 million


The return on investment is extremely sensitive to unit selling price. At $75 per ton the project would require 37 months to achieve a breakeven net present value of $4 million, corresponding to the original capital investment.


The calculations provided assume manure from an aviary house with 45 percent moisture. Manure from high-rise complexes with moisture content of 65 percent would require a higher drying capacity with proportional increases in capital and operating costs to reduce moisture content to 15 percent.


Uzelac manufactures components for rotary drying systems that can be adapted in capacity and layout to suit specific applications. Uzelac engineers are available to review specifications and to design custom installations.


Additional information on Uzelac installations can be accessed by clicking on to the Uzelac logo on the right side of the welcome page or on or (414) 529 0240 - contact Mike Terry.


What Does the Latest Study on Eggs and Cholesterol Mean?


Mickey Rubin, PhD, Executive Director, Egg Nutrition Center


Many of you may have seen the headline this morning touting another study on eggs and cardiovascular disease, with the headline “Are eggs good or bad for you? The truth may be somewhere in between.” This is one where your readers, followers or patients may have questions. I would encourage you to read past the headline because there are some important points made by experts, including Dr. Walter Willett from the Harvard School of Public Health.


“The study results are problematic because they only asked people once about their egg consumption, then followed them for many years without checking to see if their diet had changed” according to Dr. Willett, while other experts in the same article stated that "The conclusions of this study are overblown.”


What does the latest study on eggs and cholesterol mean? See below for a brief summary of the results and the broader context:


  • This new study reported an increased risk for all-cause mortality, cardiovascular mortality, and cancer mortality.


  • However, this study was limited by the fact it only assessed diet once at the start of the study 25 years ago and then never again.
    • In contrast, a stronger study from the Harvard School of Public Health assessed diet multiple times over decades and found no link between egg intake and cardiovascular risk.


  • Several studies published just in the last year on the topic of eggs, dietary cholesterol, and cardiovascular risk contradict the findings from this new study, including the Harvard study linked above, a meta-analysis of 23 studies that found egg intake reduced the risk of coronary artery disease, as well as a global analysis across 50 countries that found no link between eggs and cardiovascular disease.


  • One point not discussed extensively in this new study or the news article is the finding that consumption of eggs was linked to a reduced risk of Alzheimer’s disease. While this should be viewed in the context of the limitations of the study described above, this is consistent with other studies on choline – a nutrient for which eggs are an excellent source - that have shown favorable results for cognitive outcomes and reducing risk for dementia.


  • Finally, recent guidance from the American Heart Association (AHA) as well as the Dietary Guidelines for Americans 2020-2025 that have assessed the totality of evidence on the topic state that eggs can be a part of heart-healthy diet patterns.
    • The AHA stated in 2019 that healthy individuals can include up to a whole egg daily in heart-healthy dietary patterns, older healthy individuals can include up to 2 eggs per day in heart-healthy diets, and vegetarians who do not consume meat-based cholesterol-containing foods may include more eggs in their diets within the context of moderation.
    • The Dietary Guidelines for Americans 2020-2025 include eggs in all recommended healthy eating patterns starting from when children are first introduced to solid foods.


As always, there are often competing headlines in nutrition science, with one study showing one thing, and another study showing the opposite. Rather than getting caught with nutrition science whiplash, it is important not to focus too much on any one study, but rather view the research in totality. As is reflected in the latest nutrition guidance, nutrient-rich eggs are an important part of healthy dietary patterns across the lifespan.


Reducing feed cost during times of high feed-ingredient prices


Kristjan Bregendahl, Ph.D.; Poultry Nutritionist, Devenish Nutrition, Fairmont MN


The cost of feed accounts for 65 percent or more of the cost of egg production. Minimizing feed cost and optimizing feed utilization and production therefore becomes paramount for ensuring profitability. The following considerations are options for lowering feed costs without compromising performance.


Diet density

The three most expensive parts of laying-hen diets are energy, protein, and phosphorus (in that order), so it is tempting to lower the dietary concentration of one or more of these in an effort to lower feed cost. This could be done by re-formulating the diets, or—if the diet program includes different diets based on feed intake—switching to a higher-intake diet (e.g., from a diet designed for 25 lb/day feed intake to 26 lb/day, which lowers diet density and feed price. However, switching to such lower-density diets is only possible if the flock is ‘overfed’ to begin with. Otherwise, lowering diet density likely backfires, because the birds need the same amount of energy (calories) and nutrients regardless of feed-ingredient prices—the birds will either increase feed consumption in an attempt to obtain the needed calories and nutrients, or the smallest birds will reduce egg-production due to the now marginally deficient diet. The loss of income from either of these consequences will offset the decreased feed cost of the lower-density diet, and may even increase feeding cost (Table 1). Even if a small loss in production is accepted as a consequence of the lower-density diet, there is a very fine balance between lowering production slightly and crashing the flock.


Table 1. Lowering the feed price by reducing energy and/or nutrients often leads to an increase in feed consumption and thus feeding cost.

Energy and/or nutrient density  Feed price         Feed consumption             Feeding cost

                                                           $/ton                        lb/day                  $/day per 1,000 birds

Original                                               300           ×             0.25               =              37.50

Reduced                                              290           ×             0.26               =              37.70


To minimize feed cost and maintaining the desired production, it is important to work closely with the feed mill and nutritionist to ensure that the diet currently fed is formulated to supply the birds with only what they require and with no excesses or deficiencies. Be prepared to share with the nutritionist information about current and desired production performance, including feed intake, egg weight, percentage egg production, and body weight. The nutritionist, in turn, will have to evaluate the dietary nutrient content, including the amino acid concentration and balance.

Using the correct rounding or minimum production amounts in diet formulation is helpful to avoid deficiencies or overages. Perhaps the diet-formulation program optimizes a given diet by using 52.435 lb/ton meat and bone meal, but the mill’s major scale needs 5-lb/ton increments and instead adds only 50 lb/ton—or, 22 lb/ton of a major ingredient is suggested, but the mill’s scales need at least 50 lb/ton inclusion rate without having to manually override a system error. So, set your diet-formulating program to use appropriate minimum production amounts and round the ingredients to match the scales’ capabilities. Also, most mixers cannot adequality mix (distribute) ingredients from the micro-bins when added at less than 1.0 lb/ton with amounts between 0.50 and 1.0 lb/ton being borderline. Even if the diet-formulation program can balance a diet using, form example, 0.35 lb/ton (0.0175%) l-threonine, most hens in the flock will likely be fed a marginally threonine-deficient diet, because the too-small amount of l-threonine cannot be adequately dispersed in the diet.


Alternative and byproduct ingredients

Most poultry diets in the USA are based on corn and soybean meal, but using other ‘alternative’ ingredients (e.g., wheat grain, sorghum, canola meal, linseed meal) and byproduct ingredients (e.g., corn DDGS, meat and bone meal, bakery meal, corn gluten meal, wheat midds) may lower feed cost without impacting performance. A word of caution, though: The prices of these ingredient often follow those of corn and soybean meal, and the energy and nutrient contents of these ingredients are lower than those in corn and soybean meal, so the alternative or byproduct ingredients may not always ‘price in’ and lower feed cost while maintaining the desired energy and nutrient concentrations.  


Feed-grade amino acids

The diet’s protein is mainly supplied by corn and soybean meal; however, birds do not need protein per se, but rather the 20 amino acids that make up protein. When all the amino acids in the diet are supplied by corn and soybean meal, there are excesses of some amino acids. These excesses can be reduced by not formulating with a crude protein minimum and instead using digestible amino acids while allowing feed-grade amino acids to replace some of the soybean meal. Because protein is the second-most expensive part of the diet, reducing soybean meal—yet still meeting the birds’ amino acid requirements through the use of feed-grade amino acids—can be very cost effective. In organic production, only feed-grade methionine (dl-methionine and MHA-type products) is allowed, but the feed cost of conventional and non-GMO diets frequently benefits from including l-lysine•HCl, l-threonine, and possibly l-tryptophan l-isoleucine, and l-valine.


Feed enzymes

Feed enzymes improve the digestibilities of energy and nutrients in the feed ingredients. NSP enzymes work on the fiber fraction of feed ingredients and increase the digestibility of energy; these enzymes can therefore replace at least some of the added oil in the feed, or help maintain adequate energy concentration when high-fiber, low-energy byproducts are used. Phytase enzymes increase the digestibility of phosphorus in corn and soybean meal, and will therefore reduce the amount of expensive mono- or dicalcium phosphate in the diet. Feed enzymes are well studied and have been used for many years with good results, and organic-approved versions are available. Although the enzymes add cost to the feed, they easily pay for themselves in energy and phosphorus savings. That said, there are differences in both price and efficacy of the enzymes, so the choice of enzyme (brand name) should be re-evaluated on a regular basis in an effort to save on feed cost. 


Feed additives

So far, discussion has centered on the diet’s energy and nutrient contents and how to best meet the hens’ requirements. Another, sometimes substantial, cost in the diet is feed additives. Yeast, probiotics, and essential oils are often added to improve the birds’ production or feed utilization through increased health or improved food safety. Many, but not all, of these feed additives are well-researched, their mode of action known and shared with customers, and confer significant benefits to the flock. However, multiple, similar feed additives with overlapping effects are sometimes added to poultry diets with minimal or no additional benefit to bird health and only increase cost to the producer. In these cases—or when unproven feed additives are used—all feed additives should be reviewed to determine if one or more can be eliminated or if less expensive, but equally effective, versions (i.e., different brand names) can be used.

Sometimes, feed additives are added to control parasites (e.g., intestinal worms or coccidia), but these additives are often expensive per treated ton of feed, and their effectiveness variable. While there certainly may be benefits of using these feed additives to prevent parasites, there are cost advantages in using them only when necessary, rather than continuously. Work with the nutritionist and veterinarian to choose the best option for your particular circumstances.

Mycotoxin binders can be useful when there are high concentrations of mycotoxins present in the feed ingredients or when the risk of mycotoxins in feed ingredients is high, but they are too expensive to add routinely. In addition, some mycotoxin binders are more effective than others against certain mycotoxins, so work closely with the feed mill to determine the mycotoxin risks and with the nutritionist to select the most appropriate and cost-effective binder for your situation.


Take-home message

When feed-ingredient prices are high, the first step in attempting to save on feed cost is to make sure the current diet’s energy and nutrient concentrations closely match the need of the specific flock with no excesses or deficiencies. Additionally, alternative feed ingredients can be considered, the feed utilization optimized using enzymes and feed-grade amino acids, and the use and choice of feed additives re-evaluated.


Validating Feed Mixing with Micro-Tracers®


Article by David and Zachary Eisenberg


Microtracers® are used worldwide to assure quality of mixed feeds. They are used to identify the presence of additives and premixes in final feeds and to confirm the integrity of proprietary pharmaceuticals. In the poultry industry Microtracers® validate cross-contamination control procedures to prevent violative residues. This article describes the procedure to verify the accuracy of feed mixing.


The cost of validating the accuracy of mixers is trivial when compared with the costs of non-uniform diets that may impact animal performance. Inefficient mixer performance will require longer mixing times or smaller batch sizes than needed, wasting resources and reducing feedmill capacity. 


Microtracers® provide significant advantages over alternate tracers used to validate mixing including assays of amino acids, minerals and salt.


  • Microtracers® can be assayed either in a mill by non-technical personnel or in a feed laboratory. Assays are conducted rapidly and at a fraction of the cost of amino acid or mineral analyses. 
  • Microtracers® are added to feeds at 50 parts per million (ppm) or less as compared with salt added at 2% (20,000 ppm). 
  • Microtracers® are added to feeds as a discrete inclusion. Results obtained are not confounded by background levels of amino acids, minerals or salt in feed.
  • Microtracers can be used to detect extremely low levels of cross-contamination, by analyzing sequential samples. 
  • Microtracers® are included in the Standard of the American Society of Agricultural and Biological Engineers (ASABE) (USA) and in the GMP+ Test Methods (Holland). 


The four steps to validate mixer performance using Microtracers® are:-

  1. Addition of the Microtracer® to the feed
  2. Sampling the feed after mixing 
  3. Analyzing the feed samples for the Microtracer® 
  4. Interpreting data 


1) Addition of the Microtracer® to the Feed


The most common analytical procedure uses Microtracers® F. comprising 25,000 particles/gram. This Microtracer® is added to the trial feed at 50 grams per 2,000-lbs of feed or bulk feed premix to yield an expected 103 particles/colored spots from analysis of 75 gram subsamples.

The Microtracer® should be mixed in the proportion of 1 part tracer with 9 parts of extender such as limestone powder to simulate commercial practice where critical micro ingredients such as vitamins, minerals or drugs are added to a feed as a premix.

The Microtracer® premix should be added to the mixer at the same position and time that other micro ingredients are added -- whether by hand or from an automated microbin. 

 For paddle mixers, two different colored Microtracer® F products should be added with one at each end of the mixer. This allows validation of end-to-end distribution of the tracer in the mixer.

Two or even three mixing times can be validated in one test batch by adding different colors of tracer sequentially into the batch.

For example Microtracer F-Blue could be added at the time the mixer is fully loaded; Microtracer F-Red after one minute and Microtracer F -Orange after two minutes. Then the mixer could be left to mix for an additional minute. For the samples taken, the Blue tracer will have mixed 3 minutes, the Red for 2 minutes and the Orange for one minute. 


2) Sampling Feed After Mixing

The location of sampling depends on the purpose of the trial. 

  • To validate performance of the mixer, samples are obtained from within the mixer at different locations and depths. 
  • To evaluate the mixing quality of the feed or premix at the point of transfer from the mixer, samples should be taken at the point of discharge. 
  • To evaluate the mixing quality of the feed or premix prior to delivery, samples can be obtained directly from the vehicle discharge auger or from bags of feed.

Variability in mixing usually increases after discharge from the mixer science feed with tracer may commingle with feed not containing the tracer as cross contamination from prior batches of feed or premix may occur. 

A minimum of ten samples is recommended per batch. All samples must be discrete (not composites) and they should not be mixed prior to analysis since this reduces the power of the test. Tracer counts should be obtained from 75 g. units of feed not 200 g. units. A minimum of 200g per sample is recommended to permit retests if required.

In taking samples, safety must be the highest priority. It may be necessary to shut off power to a mixer if samples are taken from within a mixer or to a screw conveyer when samples are taken from the screw conveyer. Hands must never be placed between the conveyer screws even if power is shut off.


3) Analyzing the Microtracer® in Feed

The analytical procedure is summarized below:-

  • Lift the subsample from the top of the sample bag and weigh it in a weigh scoop or dish on a laboratory scale (75 suggested). 
  • Pour the sample through the upper hopper of a “Rotary Detector” laboratory magnetic separator to isolate the tracer on a sheet of filter paper resting over the rotating magnet. 
  • Brush the magnetically retrieved material including Microtracer® into a small aluminum weigh scoop and use a bulk tape eraser to “demagnetize” the material.
  • Sprinkle the retrieved material onto a large, 7 inch (18cm) diameter filter paper and use an artist's fan-shaped brush to disperse the tracer evenly on the test paper.
  • Use a polyethylene spray bottle with special head to “mist” the developing solution of 50% ethyl alcohol over the surface of the filter paper. As soon as colored spots begin to develop, transfer the test paper to a pre-heated hot plate or oven to dry the paper and “fix” the spots.
  • Determine the number of spots by eye using a hand-held counter or use a Microtracer® spot-counting app. (free download for Android and iOS devices). 

The Microtracer® “Rotary Detector” and peripherals including “bulk tape eraser”, hot plates, grinder (to reduce feed pellets to mash for analysis), filter paper as well as Microtracers® F can be purchased form Micro-Tracers, Inc., San Francisco.

A video of the rotary detector analytical procedure can be found at this link.

4) Interpreting Data

Microtracer® F particles yield colored spots that are counted as described above. Comparison of values is governed by Poisson particle statistics and the Chi-Squared test rather than percentage Coefficient of Variation (CV%) .

Click here for more information on the statistical interpretation of Microtracers® results.

Data is entered into either the Microtracer® Web Portal or App. (data input into one will sync to the other). The Portal or App will then calculate all statistics and provide a determination whether the mix is complete.

Completeness of a mix is determined by applying the Chi-Square test, which yields a “Chance Probability” or likelihood. If the chance probability denoted by the trial data is greater than 5%, the result is evidence of a complete mix because any excess variability is insufficient to be “statistically significant.” Results with chance probabilities between 1% and 5% are considered “Probably Incomplete” and with Chance Probabilities less than 1% mixes are considered as “Incomplete”.

Individual data points may only be discarded for good reason, as with first and last samples. For example, if the graphed values show significantly lower tracer recovery in the first and last sample taken from the mixer discharge, it may be concluded that cross contamination from prior batches of feed or premix occurred. By omitting those values, it can be determined that the intermediate samples were adequately mixed.



Microtracers® assay is the method of choice for validating feed mixing. The procedure can be performed on-site by mill personnel, rapidly providing valuable information at low cost. Free software, data interpretation, and support are provided by Micro-Tracers Inc. San Francisco.

Additional Comments

  • International Applications of Microtracer® Assays

Several types of Microtracers® are used to meet requirements of specific markets. In many European countries, feed manufacturers are required to attain a CV of 5% for trial results by counting tracer particles/colored spots, with the tracer added to feeds at 10 grams/metric tonne (10ppm). Special Microtracers® and methods developed by Micro-Tracers Services Europe (MTSE-Germany) have been developed to achieve these requirements.

In France, feed manufacturers achieve a CV of 5% in assays by using Microtracers RF (colored iron powder), and reading the color using a spectrophotometer applying methods developed by Tecaliman- the French Feed Research Institute.

In the USA and most of the world, feed manufacturers use Microtracers F (colored iron particles) with results interpreted using the applicable Poisson statistics and the Pearson Chi-Squared test. 

  • Reproducibility of Microtracer® Mixer Assays and Determining Cross-Contamination.

Since using Microtracers® to validate mixers is rapid and inexpensive it is possible to take large numbers of samples to evaluate a variety of parameters including mixing time, batch size, particle size of feed. Replication of data is possible using Microtracers® contributing to inexpensive, rapid and accurate evaluation of mixing accuracy.

Cross contamination can be easily determined by assaying for the Microtracer® in subsequent batches of feed in which the tracer was not added. Analyzing larger samples from these batches will increase the sensitivity of the test. For example, by analyzing 400g samples instead of the suggested 80g, a particle count of 500 would be expected if Microtracer were added at 50 grams/tonne. The proportion of cross contamination will be indicated by the actual number of particles determined divided by 500. If 25 particles were found, the cross contamination percentage would be estimated at 25/500 = 5%.



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