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 determined for silver perch, a native Australian freshwater species currently being cultured in Australia, Taiwan and China. ADCs were determined using faeces collected following settlement. Results from 11 experiments are reported. Each experiment included a reference diet and test diets, which were composed of 69.3% reference diet, 29.7% test ingredient and 1% chromic oxide (inert indicator). Ingredients tested included Australian, Danish and Peruvian fish meals, blood meal, meat and bone meals from beef and lamb, poultry meal, feather meal, soybean and canola meals (both expeller and solvent extracted 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 sorghum. ADCs for dry matter, energy and nitrogen were highest for fish meal, although several other ingredients, including some animal meals and gluten from wheat and corn, had similar ADCs for dry matter and energy. Digestible protein 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 nitrogen digestibility except for Peruvian fish meal and the two meat and bone meals, for which the availability of some amino acids was lower, possibly indicating protein damage during processing. Oilseeds and legumes also tended to have lower ADCs for some amino acids (e.g., sulphur amino acids) than for 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 diets for silver perch.