By Predrag Persak, Regional Technical Manager, EW Nutrition

In light of sustainability requirements, shortage of feed materials, and constant pressure on energy efficiency, we must rethink how we deal with all elements that impact our production. Shrinkage is one of the essential impacting elements.  

What is Shrinkage? 

In simple terms, shrinkage is the weight loss in feed or feed materials during receiving, processing, or storage. Shrinkage happens on the farm level but also in feed mills. In this article, we will focus on the latter one. Points or reasons why this happens are diverse but not unknown. Wastages, dust, pests, moisture loss, and scale deviations are some of the most important. Through time, we found efficient ways to close the doors to feather and fur pests that were stealing valuable resources and causing shrinkage. We are also good at weight control when receiving and dispatching, by thoroughly balancing the scales. But one point related to the core of feed production – and the most significant loss – is still left untackled. That is moisture loss through grinding. 

Figure 1: Points of moisture loss and addition in the feed mill 

Grinding is one central point of shrinkage

Grinding and subsequent particle size reduction is essential from many points (handling, nutritional, processing, mixing uniformity, …) and is unavoidable if we want to produce excellent feed. In the case of grinding with hammer mills, we use kinetic energy to make the hammers beat kernels to the desired size. This is a very efficient process. However, during that process, a part of kinetic energy is also transferred to thermal, increasing the temperature of the processed feed materials and resulting in the loss of one part of valuable moisture. Also, due to size reduction and enlargement of the surface, there is much more place for evaporation and moisture movement. Losses can be up to 2%. One essential parameter for high pellet quality is the particle size, but very fine grinding will result in higher shrinkage through moisture and dust losses.

Moisture is decisive  ̶  we must manage it!

The valuable moisture is needed for many reasons. One is weight. Another reason is that nutritional density for feed materials is calculated considering a certain moisture content. Additionally, moisture influences the processing parameters during the pelleting process (targeted moisture content in the conditioner should be 16-18%). Since moisture loss is unavoidable and represents the most significant part of loss or shrinkage, we must manage it. For this purpose, we must substitute lost moisture with added moisture. And in that process, we have a short time to do it properly. Usually, we don´t have enough time for so-called “soaking”. However, with the help of surfactants, the process can be speeded up.

Surf-Ace helps to keep the moisture in the feed

Surf-Ace, a liquid preservative premix for moisture optimization, which contains organic acids / organic acid salts, emulsifiers, and surfactants, helps to keep the moisture in the feed. Conditioning can be hindered by surface tension because water forms a film on the surface of the feed particles, or oil covers the particles. Surf-Ace improves water penetration and retention by decreasing surface tension. Trials show the moisture-optimizing effect of Surf-Ace.

A trial conducted in Jordan demonstrated an increase in moisture in different processing phases (feeder, heater, and the final product). It also showed better maintenance of water in the product during storage (Fig. 2).

Figure 2: Surf-Ace achieved higher moisture levels in different phases of the feed production process

Two further trials conducted in Poland and Serbia also showed that feed millers could increase moisture in the final feed by using Surf-Ace (Fig. 3).

Figure 3: Surf-Ace provided for higher moisture content in the feed

Effective surfactants minimize shrinkage in feed

Shrinkage in times of increasing costs must be minimized by all means. The feed industry offers surfactants that keep the moisture in the feed during processing and prevent at least this part of shrinkage.

Besides the financial aspect, the optimal moisture content in feed and feed materials is important to provide high feed quality, whether concerning pellet quality or percentage of nutrients. Using surfactants, therefore, not only increases profitability but also does its bit concerning sustainability.

By Marisabel Caballero, Global Technical Manager Poultry, and Ivan Ilić, Global Manager Technical Product Applications, EW Nutrition

 

Modern large-scale feed mills operate extremely efficiently and have few variable costs that could be reduced to lower the total cost of the final feed (Stark, 2012). In light of worrying energy price hikes, feed producers, however, should reduce their electricity use per unit produced, to maintain profitability. Find out how optimizing the feed mill’s moisture management increases feed quality while decreasing the energy required to produce it.

Due to climatic challenges, variability in raw material quality, and technical constraints, it can be challenging for feed producers to stabilize the water content in compound feed across time, raw material batches or even different machinery.

Combined with high temperatures, high moisture in feed can favor the growth of molds. They spoil feed, depleting energy and nutrients and generating reactive oxygen species (ROS) that reduce feed palatability. Even worse, some molds release toxins harm animals’ health and performance. On the other hand, low moisture levels in feed has a negative impact on pellet durability, increasing fines, process loss, and energy consumption while decreasing pellet press yield (Moritz et al., 2002).

What does feed moisture management have to do with a feed mill’s electricity consumption?

Moisture from raw materias can be lost during storage and processing. Silo aeration and enviroment conditions can contribute to moisture loss when the grains are stored at higher than optimal moisture levels (Angelovič, 2018). During feed processing, the intense friction of grinding results in heat and moisture from the grains is lost as vapor. As an optimal level of moisture is critical to ensure production output and feed quality, it must be added back to the system and adequately managed to keep or increase final feed quality.

For pelleted feeds, managing moisture is a two-step process:

1. Adding moisture in the mixer. This ensures that the mash feed is enters the conditioning process at the right moisture level, facilitating the penetration of steam and increasing the efficiency of the process.
2. Managing steam during conditioning. Steam added to the conditioner must be dry (meaning saturated with water droplets in suspension), and when this dry steam contacts the feed, it condenses and adds moisture.

However, simply adding water into the mixer does not give optimal results: Pure water does not completely bind to the feed; it mostly “sits on top” of the feed surface, increasing its water activity, and thus increasing the danger of microbial growth. Plus, a high proportion of pure water evaporates again when the feed is cooled.

Surfactants improve moisture retention

Surfactants change the way water behaves: by reducing the surface tension of water, they enable the feed particles to absorb the water and ensure that it is evenly distributed throughout the feed.

Improved moisture retention can:

• facilitate the starch gelatinization during conditioning (important making the pellet more durable and the feed more digestible),
• minimize feed shrinkage,
• reduce friction and hence the energy required for the pellet die (improving milling efficiency), and
• curb microbial growth by reducing water activity.

SURF•ACE: Improve throughput and reduce energy requirements

While surfactants contribute to mold control, feed producers also require the help of organic acids such as propionic acid (cf. Smith et al., 1983). The objectives are to optimize the moisture content in feed and to reduce its mold contamination. EW Nutrition’s SURF•ACE^TM feed mill processing aid combines organic acids and surfactants to achieve the objective of adding moisture without risking either the significant loss of moisture during cooling or the development of mold.

The effect of adding SURF•ACE to diets with different levels of fat was evaluated at more than 40 feed mills, with production capacities ranging from 5 to 20 tons per hour. SURF•ACE is added to water sprayed during mixing. This hydrating solution lubricates the mash feed, improves steam penetration and starch gelatinization, and reduces friction in the pellet dies. The results show that, relative to pure water, the addition of SURF•ACE increases press throughout (t/h) by between 5 and 25 %.

Trial results: SURF•ACE increases press yields while lowering energy consumption

• For a trial at a Turkish beef and poultry feed mill, the same feed was run through the pelletizer in two batches, one with a 1 % water and one with 1% water mixed with 200 g of SURF•ACE per ton of feed. Adding SURF•ACE resulted in higher pellet output (6% for beef; 9% for poutry) and reduced energy consumption (13% for both beef and poultry):

• In Poland, another trial conducted at a commercial feed mill found that when SURF•ACE was added to 1% mixer-moisture, this lead to a 28.6 % higher feed throughput in the pellet press, 23 % lower energy consumption per unit produced during the pelleting process, and a nearly 1 %-point higher moisture content in finished feed. This resulted in higher profitability: based on the costs in Poland at the time of the trial, an ROI of 2.4:1 was achieved.

• A recent trial at an Indian feed mill evaluated the difference between adding 1% moisture to produce crumble feed (control group) and upgrading the water with 200 g of SURF•ACE per ton. The addition of SURF•ACE reduced power consumption by 6% and improved throughput by 18%.

Feed mills must deal with rising energy costs head-on

Operating in a tight margin environment, feed mills always need to prioritize efficiency. The advantages of using SURF•ACE feed mill processing aid are clear: reduced energy consumption, better pellet quality, fewer fines, better PDI, moisture optimization, lower maintenance costs, and higher productivity (throughput). During times of increasingly high ingredient and energy costs, it is even more important to utilize savings opportunities at every production stage. Thanks to its dual surfactant and preservative effects, SURF•ACE enables feed mills to improve feed quality and increase throughput while lowering electricity use.

References

Angelovič, Marek, Koloman Krištof, Ján Jobbágy, Pavol Findura, and Milan Križan. “The effect of conditions and storage time on course of moisture and temperature of maize grains.” BIO Web Conferences 10 (2018): 02001. https://doi.org/10.1051/bioconf/20181002001

Moritz, J. S., K. J. Wilson, K. R. Cramer, R. S. Beyer, L. J. McKinney, W. B. Cavalcanti, and X. Mo. “Effect of Formulation Density, Moisture, and Surfactant on Feed Manufacturing, Pellet Quality, and Broiler Performance.” Journal of Applied Poultry Research 11, no. 2 (2002): 155–63. https://doi.org/10.1093/japr/11.2.155.

Smith, Philip A., Talmadge S. Nelson, Linda K. Kirby, Zelpha B. Johnson, and Joseph N. Beasley. “Influence of Temperature, Moisture, and Propionic Acid on Mold Growth and Toxin Production on Corn.” Poultry Science 62, no. 3 (1983): 419–23. https://doi.org/10.3382/ps.0620419.

Stark, Charles. “Feed manufacturing to lower feed cost”. Presentation at Allen D. Leman Swine Conference, Volume 39, 2012. https://conservancy.umn.edu/bitstream/handle/11299/139624/Stark.pdf?sequence=1

Why moisture management requires both surfactants and organic acids

Moisture management starts with monitoring certain indicators. The moisture content measures the total amount of water contained in a substance, usually expressed as a percentage of the total weight. Feed manufacturers track the moisture contents of raw materials, mash feed, and pellets during all processing stages  to optimize quality, yields, and profitability.

For the purpose of preventing mold growth, however, another indicator is even more critical: water activity (a_w) is technically defined as the ratio of partial vapor pressure of water in a substance to the partial vapor pressure of pure water under the same temperature and pressure conditions. What this captures is the energy state of water in a substance, i.e. its potential for (bio)chemical activity, including the growth of bacteria, yeasts, and molds. Simply put, microorganisms will usually not grow below a certain water activity level, and the higher the water activity, the higher the chance of microbial growth (Roos, 2003).

Minimum water activity (a_w) for growth and toxin production of toxigenic fungi affecting grains

		Minimum aw
Fungal species	Mycotoxin	Growth	Toxin production
Aspergillus flavus	Aflatoxin	0.78 – 0.84	0.84
Aspergillus parasiticus		0.84	0.87
Aspergillus ochraceus	Ochratoxin	0.77	0.85
Penicillium aurantiogriseum		0.82 – 0.85	0.87 – 0.90
Penicillium viridicatum		0.80 – 0.81	0.83 – 0.86
Aspergillus ochraceus	Penicillic acid	0.77	0.88
Penicillium aurantiogriseum		0.82 – 0.85	0.97
Penicillium patulum	Patulin	0.81	0.95
Penicillium expansum		0.82 – 0.84	0.99
Aspergillus clavatus		−	0.99
Fusarium verticillioides	Fumonisins	0.88	0.93
Fusarium proliferatum		0.88	0.93

Adapted from Magan, Aldred, and Sanchis (2004)

Can we condition feed with pure water?

Why does this matter? The intense friction during grinding and mixing results in heat; subsequently, moisture from the mash feed is lost in the form of vapor. These losses need to be mitigated, when the feed is too dry, the milling equipment cannot function optimally and the pellet quality deteriorates. However, simply adding water does not work well: Pure water does not readily bind to the feed; it effectively “sits on top” of the feed surface, increases the feed’s water activity and thus becomes a perfect substrate for microbial growth. Plus, pure water steam largely evaporates again when the feed is cooled.

Surfactants

Hence, at the conditioning phase, it is critical to add surfactants to the hydrating solution. Surfactants change the way water behaves: by reducing the surface tension of water, they enable the feed particles to absorb the water and ensure that it is evenly distributed throughout the feed. There are numerous beneficial effects as improved moisture retention

• facilitates the starch gelatinization during conditioning (important for pellet digestibility and durability),
• minimizes feed shrinkage at the cooling stage,
• reduces friction and hence the energy required for the pellet die (improving milling efficiency), and
• curbs microbial growth by reducing water activity.

While surfactants contribute to mold control, feed manufacturers also require the help of organic acids to optimize the moisture content in feed while reliably preventing mold (re)contamination hazards along the distribution chain.

Organic acids

Let us consider how the most effective one, propionic acid, works: In its non-dissociated state, propionic acid has all its hydrogen ions attached to the molecule. Once it enters a mold cell, the propionic acid dissociates, meaning the hydrogen ions separate from the molecule. They reduce the intracellular pH in the mold cell and inhibit its metabolic pathways, ultimately leading to cell death (Smith et al., 1983).

Common feed ingredients such as soybean meal, maize, wheat, barley, and dehulled oats are often stored for several months. Given variable and likely challenging temperature, oxygen, and moisture conditions, their water activity levels can easily escalate (Mannaa and  Kim, 2017) – rendering the long-lasting anti-fungal activity of targeted organic acid preconditioning even more important.

SURF•ACE: Improve mill performance and pellet quality

A synergistic blend of organic acids and surfactants can achieve the objective of adding moisture without risking either the subsequent loss of moisture during cooling or the development of mold. This is the working principle behind SURF•ACE^TM feed mill processing aid, carefully formulated to best achieve the dual objective of higher feed quality and higher production efficiency. This objective is achieved in concordance with optimal resource use and lower energy requirements, thus also contributing to the feed industry’s environmental commitments.

Improved press yield

The effect of adding SURF•ACE to diets with increasing levels of fat were evaluated at more than 40 feed mills, with production capacities ranging from 5 to 20 tons per hour, under identical electricity consumption conditions. The results show that the addition of SURF•ACE to the preconditioning solution increases press throughout (t/h), relative to pure water preconditioning, by between 9 and 23 %, depending on how much preconditioning solution is applied and the level of fat in the diet:

Addition of SURF•ACE increases press throughput

*Including large volumes of hydrating solution in high-fat diets might adversely affect the durability values of the feed

 

What is the role of fat in this scenario? Dietary fat acts as a lubricant between the feed and the pellet die, reducing the pressure within the die. The higher the percentage of fat included in the mixer, the lower the energy required to process the mash (Pope, Brake, und Fahrenholz, 2018). The surfactants contained in SURF•ACE have an emulsifying effect; they help bind water to the fat element of the feed. The emulsion of water and fat “behaves” like fat, improving the lubrication of press and generating a higher throughput for the same electricity consumption.

Higher pellet quality

Importantly, adding SURF•ACE does not negatively affect pellet durability, a common issue in high-fat diets (Moritz et al., 2003). On the contrary, it enhances pellet durability as more crystal starch becomes gelatinized. This translates into improved results for Holmen pellet durability testing:

Addition of SURF•ACE improves pellet durability

Pellets need to withstand significant pneumatic handling, for example, during bagging and transport, and in the feed lines. The Holmen durability tester simulates this handling, and calculates the percentage of fine generated, expressed as a pellet durability index (PDI). Across six different poultry compound feed types, SURF•ACE improves pellet quality and thus the PDI. Fewer fines equate to less reprocessing for feed manufacturers and higher palatability for animals.

The next level in compound feed production

Achieving optimal moisture levels in compound feed is a complex balancing act involving technical constraints, raw material variability, microbial challenges, and the price pressures of competitive feed markets. Feed mills generally operate within a particular comfort zone, a throughput and quality level at which they minimize production problems. Thanks to its dual surfactant and preservative effects, SURF•ACE feed mill processing aid expands the comfort zone in two dimensions: From an economic point of view, the improved lubrication gives mills the choice of either pushing their performance levels closer to their equipment’s potential capacity or achieving the same results at lower electricity use. From a feed quality angle, effective mold prevention and improved pellet quality allow for safer, more palatable feed – and from there we come full circle, to safe, nutritious food for all of us.

References

Magan, Naresh, David Aldred, and Vicente Sanchis. “The Role of Spoilage Fungi in Seed Deterioration.” Essay. In Fungal Biotechnology in Agricultural, Food, and Environmental Applications, edited by Dilip K. Arora, 311–23. New York: Marcel Dekker, 2004.

Mannaa, Mohamed, and Ki Deok Kim. “Influence of Temperature and Water Activity on Deleterious Fungi and Mycotoxin Production during Grain Storage.” Mycobiology 45, no. 4 (2017): 240–54. https://doi.org/10.5941/myco.2017.45.4.240.

Moritz, J. S., K. J. Wilson, K. R. Cramer, R. S. Beyer, L. J. McKinney, W. B. Cavalcanti, and X. Mo. “Effect of Formulation Density, Moisture, and Surfactant on Feed Manufacturing, Pellet Quality, and Broiler Performance.” Journal of Applied Poultry Research 11, no. 2 (2002): 155–63. https://doi.org/10.1093/japr/11.2.155.

Moritz, J. S., K. R. Cramer, K. J. Wilson, and R. S. Beyer. “Feed Manufacture and Feeding of Rations with Graded Levels of Added Moisture Formulated to Different Energy Densities.” Journal of Applied Poultry Research 12, no. 3 (October 1, 2003): 371–81. https://doi.org/10.1093/japr/12.3.371.

Pope, J. T., J. Brake, and A. C. Fahrenholz. “Post-Pellet Liquid Application Fat Disproportionately Coats Fines and Affects Mixed-Sex Broiler Live Performance from 16 to 42 d of Age.” Journal of Applied Poultry Research 27, no. 1 (March 1, 2018): 124–31. https://doi.org/10.3382/japr/pfx054.

Roos, Y. H. “WATER ACTIVITY | Effect on Food Stability.” Essay. In Encyclopedia of Food Sciences and Nutrition Second Edition, edited by Luiz Trugo and Paul M. Finglas, 6094–6101. Cambridge, MA: Academic Press, 2003.

Smith, Philip A., Talmadge S. Nelson, Linda K. Kirby, Zelpha B. Johnson, and Joseph N. Beasley. “Influence of Temperature, Moisture, and Propionic Acid on Mold Growth and Toxin Production on Corn.” Poultry Science 62, no. 3 (1983): 419–23. https://doi.org/10.3382/ps.0620419.