No abstract

Two feeding trials were performed on rainbow trout of mean initial weights of 40 and 50 g and lasting for 12 and 14 weeks, respectively. In trial 1, diets contained per kg 300 g fish meal and varying proportions of gelatinized maize starch plus either casein or hydrolyzed feather meal. Dietary crude protein content varied from about 27 to 53%. In trial 2, all diets had about 45% crude protein. Fish meal (300 g/kg) was replaced in 3 steps by hydrolyzed feather meal either without or with supplementation of L- lysine.HCl and/or DL-methionine. In trial 1, efficiency of utilization of digestible energy (DE) rose from 38 to 50% when the ratio digestible crude protein (DCP)/DE was increased from about 11 to 17 g/MJ irrespective of the source of additional DCP, but did not further increase at higher ratios DCP/DE. Efficiency of utilization of DCP was about 50% as long as the ratio DCP/DE did not exceed 17 g/MJ. With progressing replacement of fish meal by hydrolyzed feather meal, efficiencies of utilization of DE as well as of DCP were reduced, the respective rates of reduction being about halved by supplementing lysine with no effect of supplementing methionine.

Zusammenfassung Weizen und Weizenstärke als mögliche Quellen von verdaulicher Energie für Regenbogenforellen (Onkorhynchus mykiss) An Regenbogenforellen wurden acht Futtermischungen gefuttert, in denen entweder zu 25 oder zu 45% eine der folgenden Komponenten enthalten war: unbehandelter Weizen, hydrothermisch behandelter Weizen, rohe Weizenstärke, Weizenquellstärke. Der Gehalt an verdaulicher Energie (DE) in den übrigen verwendeten Mischungskomponenten (Casein, Weizenkleber, Fischöl) war aus vorangegangenen Untersuchungen bekannt. Die Summe aus zu testender Komponente und Casein machte in jeder Mischung 75% aus. Jeder Mischung war Cr2O5 als inerter Marker zugesetzt. Kot wurde durch Abstreifen gewonnen. Für jede zu testende Komponente war der DE‐Gehalt bei einem Mischungsanteil von 45% niedriger als bei 25%. Ausgedrückt als Funktion des Mischungsanteils L ergab sich für die einzelnen Komponenten folgender Gehalt an DE (MJ/kg Trockensubstanz): 22.8 – 0.36 L für unbehandelten Weizen; 22 2 – 0.20 L für hydrothermisch behandelten Weizen; 8.9 – 0.08 L für rohe Weizenstärke; 18.5 – 0.20 L für Weizenquellstärke. Die Verdaulichkeit des Rohproteins war für alle Mischungen mindestens 96% und zeigte keine negative Beeinflussung durch Steigerung des Proteingehaltes der Mischung.

7 diets were prepared containing as their only source of protein one of the following feeds: fish meal, casein, hydrolyzed feather meal, grieves, wheat gluten, maize gluten, soybean meal. Crystalline amino acids were supplemented except in cases of fish meal and casein to prevent specific amino acid deficiencies. Concentrations of N x 6.25 ranged between 436 and 457 g/kg dry matter (DM). Cr2O3 was added to each diet for indirect determination of digestibilities. Each diet was fed to triplicate groups of 20 rainbow trout of an average initial weight of 60 g. After 66 feeding days, all trout were killed and used for whole body analyses. Due to severely reduced intake, trout fed the casein based diet gained only about half as much weight as trout fed the fish meal based diet, though at the same fed conversion ratio of 1.0 kg gain per kg dietary DM. Gains on the other diets ranged between these two treatments with poorer feed conversion ratios. Digestibilities of crude protein of fish meal, casein, hydrolyzed feather meal, grieves, wheat gluten, maize gluten and soybean meal were: 86, 98, 67, 81, 97, 87, and 94%, respectively. The corresponding contents of digestible energy were: 21.2, 21.8, 15.4, 16.5, 19.6, 18.3, and 14.4 Mj/kg DM. Efficiency of utilization of digestible energy ranged between 43 and 54%, that of digestible crude protein between 32 and 41%.