NET IS BETTER THAN GROSS !


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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).