Determination of endogenous amino acid losses in poultry by different methods

In the first experiment 32, 8 weeks old broiler chicks were kept in idividual cages. Endogenous amino acid losses (EAAL) of birds were determined by three different methods. Chicks were either fasted, force fed with N-free diet or fed with diets containing graded amount of extracted soybean meal as a sole protein source. Both in the first and second methods 6 animals were used. In the third procedure 20 chicks were devided into 4 groups. Birds in the different groups were fed diets, containing graded levels of crude protein (5, 10, 15 and 20 percent), but the same levels of metabolisable energy and crude fibre. According to this last procedure EAAL was calculated with linear regression. In a second experiment EAAL of 3 and 9 week old broilers were compared. Chicks were fed N-free diet containing TiO2 as a marker. Five replicates of two birds of the 3 week old and 1 bird of the 9 week old group were used. Both ileal and faecal samples were taken in this case. Using different methods resulted different EAAL values. The lowest EAAL was measured with fasted chicks (7.10 mg/day). Feeding N-free diet increased the average EAAL to 15.33 mg/day. Since the highest dry matter intake was registered during the regression method, the daily EAAL was the highest in this case (24.72 mg/day). However, when the daily average EAAL values were divided by the daily dry matter intakes the value which was measured with N-free diet (0.54 mg/g DM) exceeded that of the regression method (0.38 mg/g DM). Ileal EAAL of 3 week old chicks (0.27 mg/g DM intake) was significantly (P0.01) higher than that of the 9 week old broilers (0.12 mg/g DM intake). On the other hand, EAAL determined from excreta was in the older group slightly higher (0.25 and 0.22 mg/g DM intake in the 9 and 3 week old group respectively). The endogenous amino acid content of excreta of 9 and 3 week old broilers was significantly higher (P0.01) than the ileal amino acid flow. The opposite was found with 3 week old chicks. The present study demonstrate that the conventional nutritional techniques, currently used for measuring endogenous amino acid losses in poultry, produce significantly different results. The age of chicks and the place of sampling has also significant influence on the EAAL