In 12 experiments with S.C.W.L. roosters it was shown that for each of 12 feedingstuffs there was a linear relationship between feed input and the amount of energy voided as excreta. In the 24 h. period, following 21 hr. of starvation, roosters receiving no feed excreted 4.07 kcal./kg. of body weight. When dextrose was fed the energy voided as excreta did not increase with dextrose input; consequently, the true metabolizable energy (T.M.E.) value of dextrose is its gross energy value. The T.M.E. values were not affected by the level of feed input and appeared to be additive. A simple, rapid assay for T.M.E. was developed, based on gross energy assays of the test feed and of excreta voided over 24 hr. by roosters force fed the test feed and other starved over the same period.

this Bulletin. Several people provided references to TME-related publications while others provided samples of feedingstuff s for analysis; their cooperation is appreciated. The preliminary drawings for the figures illustrating cage design and construction were prepared by F. Nachbaur; final drawings and all photographs were prepared by Research Program Service, Agriculture Canada. The feed composition tables could not have been compiled without the technical help of S. Winter, R. Cochrane and L. Hope; the proximate and amino acid analyses were made, in part, by the Chemistry and Biology Research Institute, Agriculture Canada. The staff of the poultry unit of the Animal Research Centre, Research Farm provided valuable help by caring for birds and participating in bioassay work. Finally, my thanks to D. Leger for editorial assistance throughout the preparation of the Bulletin. DISCLAIMER Mention of a trade name, proprietary product, or specific equipment does not imply its approval to the exclusion of other products which may be suitable.

inary studies were designed to test two basic assumptions: 1) that the M.E. value of an ingredient is independent of the other diet components, and 2) that the value remains relatively constant irrespective of the age of type of bird to which

Two experiments were made with S.C.W.L. roosters to test the hypothesis that the apparent M.E. value of a feedingstuff is affected by the level of intake. In the first experiment the birds were starved for 18 hr. and then fed varying amounts of whole wheat. Excreta voided during the 24 hr. experimental period was collected quantitatively and assayed for gross energy. Energy voided as excreta increased in a linear manner as the intake of wheat increased. The apparent M.E. value also varied with wheat consumption according to the equation M.E. (kcal./g.) = 3.17X - 8.5/X where: 3.17 kcal./g. is the true M.E. value of the wheat; 8.5 kcal. represents the sum of the metabolic fecal and endogenous urinary energy losses; and X is the weight of wheat consumed (g). A supplementary observation was that the metabolic fecal and endogenous nitrogen excretion of the roosters was 144 mg./kg./24 hr. In the second experiment corn oil was placed in the crops of starved roosters and the energy voided as excreta in 24 hr. was measured. The true M.E. value of the corn oil was 9.40 kcal./g. but the apparent value varied with intake. It is therefore concluded that the original hypothesis is correct. The findings of these experiments may explain some of the reported variations in M.E. data. A new approach to the assay for M.E. is proposed.

An experiment was made to determine if the basic methodology of the bioassay for true metabolizable energy (TME) can be applied to the measurement of available amino acids (AAA) in feedingstuffs. Administration of graded levels of glucose (0-30 g) had no effect on the excretion of 13 AA by adult roosters. Feeding graded levels of soybean meal, alone or in combination with glucose, caused linear increases in AA excretion. Methods of measuring AAA are described and the importance of correcting for metabolic and endogenous AA excretion is discussed. A bioassay for AAA which may be combined with the measurement of TME is described.1979 Poultry Science 58:668-673Samples of the soybean meal, glucose, and excreta (lg) were hydrolyzed with 6N HC1 as described by Smith et al. (1965) and AA concentrations were measured in a Beckman, Model 121M, automatic AA analyzer. The feeds and excreta, if sufficient, were assayed for gross energy content in an adiabatic oxygen bomb calorimeter. The procedures used to interpret 668 at Albert R. Mann Library on December 15, 2014 http://ps.oxfordjournals.org/ Downloaded from