Ž .
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.
q 2000 Elsevier Science B.V. All rights reserved.
Keywords: Nutrition; Bidyanus bidyanus; Digestibility; Meat meal; Legumes; Oilseeds; Cereals
1. Introduction
The shift to more intensive culture practices has contributed to a global increase in Ž
aquaculture production of about 12 per annum from 1984 to 1997 Tacon and
. Dominy, 1999 . This shift has only been possible because of the increased availability of
formulated diets. In Asia, the demand for aquaculture diets increased more than fourfold Ž
. Ž
. between 1986 and 1990 Akiyama, 1991 and Tacon and Dominy 1999 predicted the
Ž .
global market for aquaculture diets was over 11 million t metric tonnes in 1997. Marine based ingredients, especially fish meals are highly sought after as the protein
source of choice for many formulated aquaculture diets. Fish meals provide high contents of essential amino and fatty acids, are low in carbohydrates, are usually well
digested and, provided they are fresh, contain few anti-nutritional factors. However, production of fish meal already uses approximately 35 of the total global fish catch
Ž
. Tacon and Dominy, 1999 . As about 4 kg of wet fish is needed to produce 1 kg dry fish
meal, if diets contain more than 17 fish meal andror the food conversion ratio exceeds 1.5:1, aquaculture entails a net loss of fish protein.
Ž The search for alternatives to fish meal is an international research priority Manzi,
. 1989; Hardy and Kissil, 1997 . In Australia, very little fish meal is produced, although
abundant supplies of lower value agricultural protein sources, such as animal meals, oilseeds, grain legumes and cereals are available. For example, about 460 000 t of meat
meal, 860 000 t of canola, 1.4 million tonnes of lupins, 300 000 t field peas and 19.4
Ž million tonnes of wheat, are produced annually Australasian Agribusiness Services,
. 1993; ABARE, 1998 .
The determination of digestibility is the first step in evaluating the potential of an ingredient for use in the diet for an aquaculture species. In this study, digestibility
coefficients for 29 commercially available ingredients in Australia were researched. Silver perch is a native Australian freshwater finfish, which is being cultured due to its
rapid growth, high production in static earthen ponds and excellent eating qualities.
2. Materials and methods
