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High time for net energy

Dr Ioannis Mavromichalis
When was the last time you checked your formulations? If your diets are still formulated on digestible energy (DE) or metabolisable energy (ME), it is high time to question these nutrition practices. The net energy (NE) system is by far the best and most accurate system to use in all pig diets and it will enable you to better match available ingredients with actual animal needs. So, let's talk more about it!

When was the last time you checked your formulations? If your diets are still formulated on digestible energy (DE) or metabolisable energy (ME), it is high time to question these nutrition practices. The net energy (NE) system is by far the best and most accurate system to use in all pig diets and it will enable you to better match available ingredients with actual animal needs. So, let's talk more about it!

Gross energy
The total or gross energy (GE) in feed is used by the animal with a very low efficiency. For example, from 16.2 MJ GE in a kilogramme of maize, the growing animal receives only 11.1 MJ NE, with an efficiency of GE to NE at just 69%. Nearly a third of all energy is lost.

For soybean meal, the same efficiency of converting GE to NE is only 47%, and this despite the fact soybean meal contains more GE (at 17.3 MJ/kg) than maize! In contrast, the efficiency of energy utilisation in sources of lipids is much improved, with lard having 29.8 MJ NE out of 39.3 GE per kilogramme, or 76% GE/NE.

Disparity
The reason for the disparity in the efficiency of energy utilisation is found in the very nature of the nutrients bearing energy. Lipids require few digestive and metabolic processes to be oxidised for energy or deposited as fat. Starch is a bit more demanding, whereas proteins are the most difficult to be used as an energy source. In the last case, protein in excess of requirements results in a negative energy balance as the deamination process requires more energy than what is derived from it.

The same disparity in GE/NE that we observe among sources of energy is also observed when we discuss intermediate forms of energy, such as DE and ME.

Unfortunately, the coefficients of utilisation does not remain similar in proportion among different ingredients, multiplying thus the confusion! The end result is that when feeds are evaluated for their energy content different hierrarchies develop.

Take the following table for example.

Feed stuff DE (MJ/kg) Order based on digestible energy  NE (MJ/kg) Order based on net energy
Soybean meal 14.7 1 8.1 4
Wheat 13.9 2 10.5 2
Maize 13.9 2 11.1 1
Cassava 12.6 3 10 3
Wheat bran 9.3 4 6.3 5


Protein-rich ingredients
It is evident that a protein-rich ingredient like soybean meal that ranks high in the list when ordered by DE content does not fare equally well in terms of NE. It is equally interesting to note that maize and wheat, which contain similar levels of digestible energy are quite different in net energy content. This is due to the higher level of protein and the presence of anti-nutritional factors, such as polysaccharides, in wheat.

How does this translate into practical terms? It makes little difference if you use GE or NE, or anything in between, as long as you always use the same cereals and protein sources and you're achieving maximal growth in your pigs.

But, when it comes to replacing one ingredient with the other or when trying to manipulate growth performance and carcass characteristics, anything but the NE system will result in inaccuracies, with over- or under-supply of energy in relation to other nutrients. This translates to lost profitability no less!

So, check your matrix again and make sure you have NE values in there!

12 comments

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    Dr.R.Bhaskaran

    Highly useful and excellent

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    harryfernandes

    hitherto I am using maize,ragi,polishricehusk, and other ingrediyats to my piglets. This costs Rs.100 per piglets and also vegetables. Do you have any other information than this.

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    Juan Kalinowski

    More than a comment, an inquire on the availability of information about energy requirements expressed in NE, as well as NE values of feedstuffs

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    abiodun

    can i use bird feather as alternative to soya bean in the feeding of pig

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    Gerry

    Not all feed ingredients have published net energy values. Where can we get them?

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    Kwame

    May I know if cassava contains any protein.

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    Ioannis Mavromichalis

    Kwame, according to INRA2004 Tables, dried cassava root (70% starch, 97% dry matter) contains 2.5% crude protein.

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    Ioannis Mavromichalis

    Juan, I use the INRA Tables. Check the Nottingham University Press or Wageningen Academic Publishers websites. These places sell this book (it's a green one!)

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    Ioannis Mavromichalis

    Gerry, you're correct, not all ingredients have been tested for NE. Nevertheless, the French institute INRA has published well researched regression equations that predict fairly accurately the NE content in almost every feedstuff based on its chemical composition. Check my answer below to find where you can buy the Green book where you might find all the information you need.

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    Ioannis Mavromichalis

    Abiodun, hydrolyzed feather meal is not as good a protein source as soybean meal. It is deficient in lysine AND histidine. It has very low palatability. Its protein is quite undigestible and it risks the problem of Salmonella contamination. I would only use it in diets for growing-finishing pigs and gestating sows adding no more than 2% in the final feed.

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    Ioannis Mavromichalis

    Harry Fernanders, if you're satisfied with the performance of your piglets, then there is not much to add. If not, then you should consider adding some protein sources and balancing the amino acids. Also, adding some salt always helps...

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    clarisa

    I think so that using NE is much accurate than ME. But on the other side, you think it is best to formulate based on digestible amino acis rather than total?

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