Modified assay for true and apparent metabolisable energy based on tube feeding.

1. To improve the accuracy with which true metabolisable energy (TME) values of feedingstuffs are determined, a modification to the assay based on tube-feeding is proposed. 2. To ensure that the gastrointestinal tracts of the experimental birds are as empty as possible at the start of the assay it is recommended that the normal food is withdrawn 48 h before tube-feeding. 3. In order to partly alleviate the effects of starvation, all birds are given two doses of 25 g glucose (as an aqueous solution) about 40 and 16 h before tube-feeding. Birds, from which endogenous energy losses are to be derived, are fed 50 g glucose rather than given no food. 4. All birds are given 50 ml water by tube about 32 h after feeding to overcome any effects induced by low water intake. 5. A comparison of the two procedures with 8 feedingstuffs showed that the mean coefficient of variation was reduced from 5.5% to 1.5% for TME and from 4.7% to 1.8% for TME.