European reference method for the in vivo determination of metabolisable energy with adult cockerels: Reproducibility, effect of food intake and comparison with individual laboratory methods

Abstract

1. A common reference procedure adopted by several European laboratories to determine apparent metabolisable energy corrected to zero‐nitrogen balance (AME_n) is described.

2. Reproducibility has been estimated by comparing results from 4 diets measured in 7 laboratories. The standard deviations between laboratories of dry matter, gross energy, Kjeldahl nitrogen and AME_n were respectively, on average, 11.29 g/kg, 0.242 MJ/kg, 1.56 g/kg and 0.380 MJ/kg dry matter; the corresponding coefficients of variation between laboratories were 1.27, 1.29, 4.39 and 2.92%.

3. Effect of food intake was tested by comparing AME_n from birds fed either 0.90 or 0.45 of ad libitum: the amount of food intake had a negligible effect on AME_n values. Endogenous energy losses corrected (EEL_n) or not (EEL) to zero nitrogen balance were estimated either by regression between excreted energy and ingested energy or in fasted and glucose‐fed cockerels. EEL_n estimated by regression was, on average, 8.7 kJ/bird/d.; it was independent of diet composition. EEL and EEL_n determined in fasted or glucose‐fed birds were higher than those determined by regression.

4. AME_n values measured by individual laboratory procedures were very close to those obtained by the reference method, except from laboratories using a tube feeding procedure, where deviations were probably a consequence of overestimated EEL.