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NET IS BETTER THAN GROSS !


from : 123rf


In Swine and Poultry diets, energy drive the formula cost. Therefore, it is critically important that the energy content of a diet is optimized as a way to reduce feed cost. We all know that net energy is more accurate than gross. Despite this statement, we are still formulating a lot based on gross or digestible energy. We tend to believe that using net energy as formulation driver would lead to higher cost. This is a misconception that prevents many companies from moving from gross to net energy. The article below will explain how you can reduce your formula cost by 2% by using net energy as driver to formulate.


There are several systems available for the characterization of dietary energy. The most common ones - digestible and metabolizable energy - describe the energy animals can potentially derive from the feed. Net energy has been proposed as a superior system that describes the feed energy animals actually do use. The following will describe these energy systems and make the case why net energy should be adopted by feed industry.

(INRA, Jean Noblet)

Feeding refers in general, to four energy systems: - First Gross Energy (GE) is the total energy of a feedstuff or a diet. GE is determined by burning and measuring the amount of energy liberated. The animal, however, can only utilize the digestible part of the GE, and therefore a more descriptive and animal-specific method is required. - The Digestible Energy (DE) system takes into account the loss of not digested and not absorbed energy of the diet. Digestible energy is simply calculated as the gross energy (GE) minus fecal energy (both measured by burning). The energy of feces is originated from the diet and mainly from the indigestible fraction of its fiber content. In the past the use of DE was rather common in Europe, and assuming a cereal-soybean meal based diet, DE level could be approximately 85% of GE. - Because energy losses during the diet digestion refer not only to the fecal energy, but also to the losses in urine and gas, a third system: the Metabolizable Energy (ME) system occurred. This system is more accurate because energy lost in urine, can vary considerably, with high protein (increasing energy lost through urine) and high fermentable feedstuffs (increasing fermentations in the large intestine). Because most of the commercial diets are formulated close to animal requirements, the ratio of ME to DE is constant: ME for cereal-soybean meal based diets is typically around 96-97% of DE. The ME system is obviously more precise than the DE system, and is commonly used by nutritionists in the United States and in Asia. - The most accurate energy system is the Net Energy (NE) system. NE is the final step of energy retained by the animal for productive purposes: Growth, protein and fat deposition, fetus and milk production. In that system not only fecal, urinary, and gas losses of energy are accounted for, but also heat produced (due to the digestion and the maintenance). In average, the loss accounts for 25% of the ME (for growing pig) Since almost 20 years, the NE system is largely used all over Europe for Swine feed formulation. This system proves its efficiency on pigs over 25 Kg. NET ENERGY IS CHEAPER !


The main difference between DE or ME and NE is that the former two express potential energy, while the latter expresses useable energy, and includes the efficiency with which nutrients can be utilized. This efficiency is different between nutrients. Body protein is subject to a constant breakdown and synthesis process, during which a certain fraction of amino acids is inevitably lost. Protein synthesis requires energy, and the repeated breakdown and synthesis of protein increases this energy expenditure; this means that dietary protein is used with a mean efficiency of only 54% for body protein deposition. In comparison, starch and lipids are utilized for lipid deposition with a mean efficiency of 74% and 95%, respectively (de Lange and Birkett 2004).

(INRA, Jean Noblet)



Formulation is to select the cheapest way to provide the required level of energy. When looking at the Net Energy, protein sources as Soybean meal or Canola meal appear more expensive sources of energy as their gross energy would make us think. When moving to net energy formulation, the system would automatically reduce the contribution of Soybean meal and Canola meal and select cheaper sources of energy as lipids or carbohydrates. In Asia, feed formulas are traditionally very high in protein contents. This underlines a poor energy conversion of feed formulas in general and an increase of feed conversion. By substituting the protein with low energy conversion by starch sources or fat, the exploration of a net energy model would have the benefit to reduce feed conversion and either to reduce the feed cost by selecting more effective source of energy. In parallel, to maintain similar level of gross protein as requested by customers, the system will move to cheaper sources of protein with lower digestibility ratio. HOW TO CONVERT TO NE MODEL? To implement the Net Energy model, we need to update in the formulation matrix every raw material with their net energy value. Some tables are available for the most commonly used raw materials. You can find them on INRA / EVAPIG website - http://www.evapig.com or The Netherlands – CVB table (available with subscription). European nutritionists use as well NE prediction equations related to the feedstuff characteristics analyzed from various samples. You will find below 3 equations depending on the input you already have from your raw materials. All nutrients are expressed in g / kg dry matter of ingredient and NE, DE, ME are expressed in Kcalories / kg dry matter NE = (0.0121 NP + 0.0350 DF + 0.0143 Starch + 0.0119 Sugars + 0.0086 DRes)*239 NE = (0.703 DE + 0.0066 FAT + 0.0020 Starch – 0.0041 CP – 0.0041 CF)*239 NE = (0.730 ME + 0.0055 FAT + 0.0015 Starch – 0.0026 CP – 0.0041 CF)*239 (From J.NOBLET) NE = Net Energy, DE = Digestible Energy, ME = Metabolisable Energy CP = Crude Protein, NP = Net protein FAT = Fat, DF = Digestible Fat DRes = Digestible Organic Residue CF = Crude Fiber As formula requirement, we are looking for a target of Net Energy target to reach between 2,294-2,390 Kcalories / Kg Dry matter;

  • NE target for Growing pig from 25 to 60kg : 2,294 – 2,342 Kcalories/kg dry matter

  • NE target for Finishing pig from 60 to 115 kg : 2,342 – 2,390 Kcalories/kg dry matter

IT STARTS TODAY! It would take some times to move from DE or ME to the new NE model. I recommend all feedmillers to start looking at this model and experiment into 2 parallel directions;

  • You should make some simulations in your software in order to validate the economical interest for your company. Every potential gain above half percent of cost savings should become a research project for you especially on growing and finishing pig where margin are thin.

  • You should start building your materials matrix on net energy and validate the relevancy of the figures by testing the new formulas through zootechnical performance at your research center.

The availability of new materials as cereal by products or animal fat in a commercial diet would render the Net Energy system more and more relevant. More and more nutritionists all over the world used or choose to use the NE system, mainly because of the accuracy for animal performances and NE requirements. This model ensures that we make the correct arbitration between materials in order to provide sufficient energy available for maintenance, growth and reproduction. This model provides a strong correlation between Feed conversion ratio and NE level of the diet.



The consequence for diet formulation is that rations formulated under the NE system will impact the protein sources (Rademacher 2001), because the cost/Kcalories energy prohibits the inclusion of a large amount of soybean and canola meal. Proteins are not only selecting for their contribution in digestible energy but the choices are made as well to match the energy requirement. If we precise the rules of arbitration, the system will choose others ingredients with a lower cost of net energy. This requires that we open the formulas to new raw materials with higher net energy conversion as cereals, fats or molasses. This new arbitration will reduce the cost of a mixed diet by as much as 2% during the grower and finisher phases (Rademacher 2001). It is sufficiently significant for a feed mill to be explored. This could by itself become a competitive edge in term of cost optimisation strategy. It will take times and I advise you to start working on it now. Once the industry will migrate to the NE model, it may be too late to start working on the matrix. I encourage you to make some simulation in your system to validate the economical interest for your company.

Related tags: Net Energy - Formulation - Feed

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