Summary

Objectives

Obtain an early commitment from feed manufacturers (preferably Australian) to produce and market feedsTo develop coordinated and collaborative research and development to replace fish meal in feeds with cost-effective alternatives.

Non Technical Summary:

If aquaculture is to continue to expand in Australia cost-effective diets based on Australian agricultural ingredients urgently need to be developed. The replacement of fish meal as the protein source of choice is a global research priority driven by static or declining supply of fish meal and rapidly expanding aquaculture and aquaculture feed industries. Australia has very poor supplies of fish meal and other aquatic meals but fortunately has abundant supplies of agricultural ingredients with potential for use in aquaculture diets.

In recognition of the need to develop diets for Australian aquaculture species, with reduced contents of fish meal, a number of institutions independently commenced this type of research in the early 1990's. The Fisheries Research and Development Corporation (FRDC) was approached by a number of institutions to financially support this research. In response, FRDC created their first 'Sub-Program' with the aim of coordinating research to develop Australian aquaculture diets. The two primary objectives were to replace fish meal and obtain an early commitment from commercial aquaculture feed manufacturers to adopt results.

Six separate projects were formed; four on species considered to represent most 'types' of species being farmed in Australia, one on feed processing and one on a technology audit for amino acids. The four 'model' species were prawns Penaeus monodon, silver perch Bidyanus bidyanus, barramundi Lates calcarifer and Atlantic salmon Salmo salar. Each project involved a number of collaborating scientists from different institutions and all projects were coordinated through a Sub-Program Steering Committee. Regular meetings with investigators from all projects as well as feed manufacturers, ingredient suppliers and R&D corporations were held twice each year.

This report describes the subprogram administration, lists the reports produced and provides a brief summary of conclusions. Final reports for all six projects are available (see Appendix 1). In addition, collaborative research in vitro digestibility conducted on each of the four species within each of the "species" projects was reported separately. Two additional nutrition projects, which were funded by FRDC before the Sub-Program commenced, were brought under the Sub-Program umbrella. These projects were on the "development of more cost-effective salmon feeds for the Tasmanian Atlantic salmon industry" and the "dietary requirements and optimal feeding practices for barramundi". Final reports for these are also available. Results with barramundi nutrition research prompted an extension to this research to study the efficacy of crystalline amino acids and to specifically evaluate meat meal as a replacement for fish meal. Results obtained during the Sub-program, including technical workshops and separate experiments funded by other R & D Corporations to investigate particular aspects of fish meal replacement, were produced and these are also available (Please see Appendix 1 for information on how to obtain all reports).

Summary of Conclusions

• Precise and reproducible methods for determining apparent in vitro digestibility for diets and ingredients were developed (or evaluated) for prawns, silver perch, barramundi and salmon. The influence on digestibility of collection times and period, indicator type, fish size and stage, season and feeding pattern was investigated for one or more of the target species. Due to intrinsic differences between species, different methods of determining digestibility were developed. For prawns, silver perch and small salmon, faeces were collected by settlement while for barramundi and large salmon, faeces were collected by stripping.

• Digestibility coefficients for over 60 ingredients were determined for silver perch (the only omnivorous fish species targeted) and digestibility coefficients for the most promising ingredients were determined for other species.

• Rapid methods for in vitro digestibility determination were developed or evaluated and results were compared using in vivo methods. In vitro methods were very useful as qualitative rather than quantitative indications of digestibility.

• Digestive capacities of aquaculture species were determined. Barramundi and Atlantic salmon were adapted to carnivorous diets, silver perch and tiger prawns were omnivorous and redclaw crayfish and tilapia were adapted to more herbivorous diets.

• Carnivorous species had a limited capacity to digest starch while omnivorous and herbivorous species could digest starch very well. A possible pathological accumulation of glycogen in barramundi livers was identified. Not even the omnivorous silver perch could digest non-starch polysaccharides in lupins.

• Maximum practical inclusion contents for a large number of ingredients were determined using growth assays and comparative slaughter techniques to assess ingredient utilisation. Utilisation of meat meal was high for all species examined (prawns, silver perch and barramundi) and this ingredient could be used to replace 70-100% of fish meal. Other terrestrial animal proteins such as blood meal, poultry offal meal and feather meal were also well utilised in the species where they were tested. In general, plant protein sources were less well utilised. Silver perch and prawns were better able to utilise plant protein sources than barramundi and salmon. Reducing the carbohydrate content through dehulling and further protein concentration improved the potential value of these ingredients. Cooking starch-rich plant protein ingredients improved their value

• Studies on nutrient requirements concentrated on protein and protein:energy requirements:

• The maintenance requirement of P. monodon for protein and energy were 0.007g digestible crude protein, 0.3 KJ digestible energy/g body weight/day respectively.
• For silver perch fed diets with 14-15 MJ/kg digestibility energy, increasing digestible protein and digestible lysine above 25.3% and 1.5% respectively did not increase growth.
• For optimal growth rate and food conversion, barramundi held at high water temperature (26 to 29^oC) require diets high in protein and energy (>45% bprotein and protein:DE of 30mg/kj) and not less than 1.5% EPA+DHA.
• High DE diets for barramundi (>16 kj/g) were advocated as a management strategy to minimise the slow growth rate of fish held at low water temperatures during winter.

• The deterioration in amino acid profile which occurs when terrestrial protein ingredients are used to replace fish meal was considered unlikely to adversely affect barramundi performance if the dietary protein was >50% and fish were fed liberally.

• Cyrstalline amino acids were less effective than intact protein sources but were found to be more effective supplements for low protein diets than high protein diets.

• Exogenous enzyme supplements including proteases, carbohydrates and phytase were evaluated with Atlantic salmon. Only phytase elicited a growth response.

• For Atlantic salmon, adaptation to changes in the ingredient composition were identified and shown to be of great importance when assessing the performance of diets containing new or unusual ingredients.

• A survey of commercial diet pellet characteristics was completed.

• Optimal extrusion conditions for salmon and silver perch diets were described.
• An audit concluded that in the short-term, crystalline amino acids will be the major form of amino acid supplementation but development of peptic supplements has great long-term potential.

• Technologies which were identified as having possible long-term potential for the production of peptides include: chemical modification of proteins, chemical synthesis of peptides, enzymatic modification of proteins, enzymatic synthesis of peptides and generation of defined peptides by recombinant DNA technology.

• Practical diets for silver perch based on meat meal and grain legumes, with only 5 or 10% fish meal, out-performed earlier reference diets based on fish meal and soybean meal in large-scale experiments with fish grown to market size in earthen ponds.

• Barramundi diets containing high meat meal contents, with or without any fish meal, but with additional fish oil, produced equivalent production and fish with similar sensory characteristics to fish reared on fish meal-based diets.

• These results have already been commercialised. Silver perch diets with 5% fish meal, based on formulations developed during this Sub-Program, are available commercially at lower prices than earlier diets. Results for barramundi have also been adopted by industry as the basis for new commercial diets for this species. On-going evaluation of results with prawns and salmon is also attracting great commercial interest.