Repository hosted by TU Delft Library

1. The aim of the study was to determine the ideal ratio of the essential amino acids lysine (Lys), methionine (Met), threonine (Thr), tryptophan (Trp), arginine (Arg), valine (Val) and isoleucine (Ile) and to assess the required dietary lysine concentration for optimum performance in broiler chickens of 2 commercial strains from 20 to 40 d of age. 2. An identical basal diet was used throughout all experiments. It consisted mainly of maize and soyabean meal and contained 172 g crude protein and 13.2 MJ AMEN per kg. For each experiment, the basal diet was adequately supplemented with all essential amino acids except the one to be tested, which was supplemented in 6 graded concentrations in exchange for maize starch. One (Met, Trp, Arg, Val, Ile) or 2 (Lys, Thr) growth trials were conducted per amino acid tested and the response in weight gain, food: gain ratio, breast meat yield and abdominal fat were examined. 3. The ideal amino acid ratio relative to Lys (expressed as a percentage) was calculated to be 75% Met+Cys, 63% Thr, 19% Trp, 112% Arg, 71% Ile and 81% Val on a true faecal digestible basis when the data were subjected to broken-line regression analysis. From both lysine studies the concentration for optimum food: gain ratio was calculated, by exponential regression analysis, to be 11.5 g true faecal digestible lys per kg diet. © 1999, British Poultry Science Ltd.

Pea starch, hulls and cotyledon inner fibres, isolated from pea seeds, were incorporated in N-free diets, on a NDF-content basis, in order to study their effect on the ileal endogenous amino acid (AA) excretion in the growing pig. Maize starch and wood cellulose were selected as references. The inner fibre-containing diet was also supplemented with enzymatically hydrolysed casein (EHC) in order to test the peptide alimentation method on a diet containing a fibre source with a high water-holding capacity (WHC = 10.9 g water g-1 DM). The fibres were also analyzed by different methods (crude fibre, NDF, ADF, enzymatic gravimetric method, Englyst method). The fibre content of the inner fibre fraction varied widely from one method to another and ranged from 109 g crude fibre to 480 g AOAC fibre kg-1 DM. Compared to the 'maize starch + wood cellulose' diet (11.0 g AA excreted kg-1 DM intake), pea starch had no effect on ileal AA losses (9.6 g), whereas pea hulls slightly increased them (14.2 g). The AA excretion dramatically increased with the incorporation of inner fibres (28.0 g), because of their very high WHC. The addition of EHC increased the output (48.0 g) further, at a level that can hardly be explained only by an increase of the endogenous secretions. The results suggest that the NDF content of grain legume products is not indicative of their effect on the ileal endogenous AA losses in pigs and that the physiological effects of fibres along the gastrointestinal tract are due to both their chemical and physical properties.

We assessed the use of 15N-labeled dietary proteins as a possible tool for the determination of the true ileal amino acid (AA) digestibility in pigs. The first experiment was designed to study the dietary N excretion pattern at the ileum subsequent to the ingestion of a single 15N-labeled meal. In a second experiment, we compared ileal endogenous AA outputs and true AA digestibility estimates obtained in pigs ingesting 15N-labeled dietary proteins in a single meal vs. intravenous infusion of [15N]Ieucine for 10 d during the ingestion of a pea-based diet and a protein-free starch diet. The proportion of endogenous N found in the ileal digesta differed when the label was delivered orally (50%) vs. intravenously (72%) and changed with time. As a consequence, the true ileal AA digestibilities measured with labeled diets were lower. A third experiment demonstrated that this was due to the rapid recycling of labeled dietary N in endogenous moieties, because 15N was found in blood within 10 min of consuming the labeled meal, within 50 min of consumption in pancreatic enzymes, 90 min in bile and 4 h in ileal mucins. We conclude that the use of 15N-labeled meals for determination of true ileal AA digestibilities is limited by the fast recycling of dietary N in endogenous secretions following a single 15N-labeled meal. The accuracy of results will depend on meaningful estimates of AA flow during a limited period and accurate estimates of 15N in AA.