Effect of several feeding stimulants on diet preference by juvenile gibel carp (Carassius auratus gibelio), fed diets with or without partial replacement of fish meal by meat and bone meal

The objectives of this work were to study the effects of several feeding st imulants on gibel carp fed diets with or without replacement of fish meal b y meat and bone meal (MBM). The feeding stimulants tested were betaine, gly cine, L-lysine, L-methionine, L-phenylalanine, and a commercial squid extra ct. Three inclusion levels were tested for each stimulant (0.18, 0.5%, and 1% for betaine and 0.1, 0.25 and 0.5% for the other stimulants). Two basal diets (40% crude protein) were used. one with 26% fish meal (FM), and the o ther with 21% fish meal and 6% MBM, Betaine at 0.1% in the fish meal group and at 0.5% in the meat and bone meal group was used in all experiments for comparison among stimulants. In the experiment on each stimulant, six tank s of fish were equally divided into two groups, one fed the FM diet, and th e other fed the MBM diet. After 7 days' adaptation to the basal diet, in wh ich the fish were fed to satiation twice a day, the fish were fed for anoth er 7 days an equal mixture of diets containing varying levels of stimulants . Each diet contained a unique rare earth oxide as inert marker (Y2O3, Yb2O 3, La2O3, Sm2O3 or Nd2O3). During the last 3 days of the experiment, faeces from each tank were collected. Preference for each diet was estimated base d on the relative concentration of each marker in the faeces. Gibel carp fed the FM diet had higher intake than those fed the MBM diet, b ut the difference was significant only in the experiments on betaine, glyci ne and L-methionine. None of the feeding stimulants tested showed feeding e nhancing effects in FM diets. All feeding stimulants showed feeding enhanci ng effects in MBM diets. and the optimum inclusion level was 0.5% for betai ne, 0.1% for glycine, 0.25% for L-lysine, 0.1% for L-methionine. 0.25% For L-phenylalanine. and 0.1% for squid extract. The squid extract had the stro ngest stimulating effect among all the stimulants tested. (C) 2001 Elsevier Science B.V. All rights reserved.