for example, the energy values of some feed ingredients are expressed in gross energy while some researchers expressed theirs in metabolizable energy, i want to know if they can be converted to each other using a particular formular
Gross energy is the combustion value and metabolizable energy takes digestion by the animal into account.
Digestibility of feedstuffs or feeds can differ considerably; thus one formula to take digestibility into account is quite unlikely.
See also the attached table
yes you can convert your gross energy to ME values if you precisely analyse for proximate composition. The analysed values are then inputted into regression equations published by several authorities to this effect - for specific animal classes. For poultry, you can consult NRC (1994). Also you should be able to find the formula in most standard nutrition text books. But you cannot convert ME back to gross energy unless you have access to the original metabolic data. It is in fact pointless to do so.
Yes! Metabolisable energy (ME) is estimated from gross energy (GE) of the feed (Pond et al., 1995). The GE content of whole feeds or of their constituents is measured in an apparatus known as bomb calorimeter (McDonald et al., 1987). Energy lost in faeces is about 20% (DE = 0.8GE), and 5% lost in urine (ME = 0.95DE). According to Pond et al., (1995), the ME is commonly used to evaluate feedstuffs, and to establish feeding standards for poultry because faeces and urine are excreted together. Therefore, the total energy loss from faeces and urine is about 25% (ME = 75GE). Given gross energy of a feedstuff, its ME can be determined.
Animal feed tables will give you estimations of that value. But remember that those values are only the mean of some trials with a limited number of animals and feedstuffs. Experience and knowledge of your own animals behaviour will enable you to judge and select what "in your case" may be the most useful information.
The first chapters in most tables will guide you in use and interpretation of the published figures.
Good luck and enjoy your journey into animal science
I share with the views of Elly Ndyomugyenyi. If you have the value of the GE then you can estimate the ME.This is only an estimated value as the real value will be based on your particular situation and the feed-stuff used.
If you want to convert GE to ME, do not forget to consider that different quality of feed has different result.
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