Replacement of fish meal in diets for Australian silver perch, Bidyanus bidyanus: I. Digestibility of alternative ingredients

Apparent digestibility coefficients (ADCs) for dry matter, nitrogen, energy and individual amino acids for 29 commonly used feed ingredients were dete rmined for silver perch, a native Australian freshwater species currently b eing cultured in Australia, Taiwan and China. ADCs were determined using fa eces collected following settlement. Results from 11 experiments are report ed. Each experiment included a reference diet and test diets, which were co mposed of 69.3% reference diet, 29.7% test ingredient and 1% chromic oxide (inert indicator). Ingredients tested included Australian, Danish and Peruv ian fish meals, blood meal, meat and bone meals from beef and lamb, poultry meal, feather meal, soybean and canola meals (both expeller and solvent ex tracted for each), full fat soybeans, peanut meal, cottonseed meal, linola, two species of lupins, field peas, faba beans, chick peas, vetch, cow peas , wheat gluten, corn gluten meal, two cultivars of wheat, millrun and sorgh um. ADCs for dry matter, energy and nitrogen were highest for fish meal, althou gh several other ingredients, including some animal meals and gluten from w heat and corn, had similar ADCs for dry matter and energy. Digestible prote in from these ingredients was in the range 52-86% compared with 63-69% for fish meals. Silver perch were capable of digesting protein very effectively in almost all ingredients tested. Amino acid availability reflected nitrog en digestibility except for Peruvian fish meal and the two meat and bone me als, for which the availability of some amino acids was lower, possibly ind icating protein damage during processing. Oilseeds and legumes also tended to have lower ADCs for some amino acids (e.g., sulphur amino acids) than fo r other amino acids. Differences in ADCs for nitrogen and individual amino acids indicate the need for individual amino acid availability data. The data provided a useful starting point for least-cost formulation of die ts for silver perch. (C) 2000 Elsevier Science B.V. All rights reserved.