The lipid composition and biochemistry of freshwater fish.

Trace minerals in fish nutrition

The evaluation of feed ingredients is crucial to nutritional research and feed development for aquaculture species. In evaluating ingredients for use in aquaculture feeds, there are several important knowledge components that should be understood to enable the judicious use of a particular ingredient in feed formulation. This includes information on (1) ingredient digestibilities, (2) ingredient palatability and (3) nutrient utilization and interference. Diet design, feeding strategy, faecal collection method and method of calculation all have important implications on the determination of the digestible value of nutrients from any ingredient. There are several ways in which palatability of ingredients can be assessed, usually based on variable inclusion levels of the ingredient in question in a reference diet and feeding of those diets under an apparent satietal or selfregulating feeding regimes. However, the design of the diets, the parameters of assessment and the feeding regime can all be subject to variation depending on subtleties of the experimental design. Clearly, issues relating to feed intake are the key performance criteria in palatability assessments, and it is important that such experiments maintain sufficient stringency to allow some self-discrimination of the test feeds by the fish. The ability of fish to use nutrients from the test ingredient, or defining factors that interfere with that process, is perhaps the most complex and variable part of the ingredient evaluation process. It is crucial to discriminate effects on feed intake from effects on utilization of nutrients from ingredients (for growth and other metabolic processes). To allow an increased focus on nutrient utilization by the animals, there are several experimental strategies that can be adopted, which are based on variations in diet design and feeding regime used. Other issues such as ingredient functionality, influence on immune status and effects on organoleptic qualities are also important consideration in determining the value of ingredients in aquaculture feed formulations. A key aspect to note is the need to design all experiments with sufficient experimental capacity to detect significant effects.

A feed is only as good as its ingredients – a review of ingredient evaluation strategies for aquaculture feeds

Publisher Summary Varying egg quality is one of the limiting factors for successful mass production of fish fry. It may also cause some of the variability in recruitment observed in many wild stocks, since poor egg quality may decrease the survival potential of the hatched larvae. In the literature, the term egg quality has been defined and used in various ways by different authors. Due to the limited knowledge in the field, it has been difficult to pinpoint valid quality criteria. The only definition of egg quality that has general validity is probably the egg's potential to produce viable fry. The egg's potential to produce viable fry is determined by several physical, genetic, and chemical parameters, as well as the initial physiological processes occurring in the egg. If one of the essential factors is lacking, or is incomplete, egg development will fail at some stage. Thus, egg quality should be regarded as determined when the egg has left the female fish and the fertilization process is complete. This definition is, however, of very little practical value, since fry viability obviously cannot be determined before the fry is produced. Good practical criteria for the determination of egg quality should be both possible to identify early in development, and be simple to use. The problems of egg quality have received increasing attention, in relation to cultivation as well as to the assessment of reproduction of wild fishes. This chapter discusses the possible criteria for the determination of quality of fish eggs.

Egg Quality in Fishes

Chitin is the (1→4)-β-linked homopolymer of N-acetyl-D-glucosamine (Fig. 1). The individual polymer chains can be thought of as helices, as each sugar unit is inverted with respect to its neighbors. This leads to their stabilization as rigid ribbons by 03—H … 05 and 06—H … 07 hydrogen bonds. The commonest form of chitin is α-chitin. Its unit cell is of two N,N‵-diacetylchitobiose units of two chains in an antiparallel arrangement. Thus, adjacent polymer chains run in opposite directions, held together by 06—H … 06 hydrogen bonds, and the chains are held in sheets by 07 … H—N hydrogen bonds (Minke and Blackwell, 1978). This gives a statistical mixture of CH2OH orientations, equivalent to half oxygens on each residue, each forming inter- and intramolecular hydrogen bonds. This results in two types of amide groups; all are involved in the interchain C=O … H—N bonds, while half of the groups also serve as acceptors for 06—H … O=C intramolecular bonds. This extensive intermolecular hydrogen bonding leads to a very stable structure, the individual polymer chains eventually giving rise to microfibrils if allowed to crystallize (Gooday, 1983). A less common form of chitin is β-chitin, in which the unit cell is of one N,N‵diacetylchitobiose unit, giving a polymer stabilized as a rigid ribbon, as for α-chitin, by 03—H … 05 intramolecular bonds (Gardner and Blackwell, 1975). Chains are then held together in sheets by C=O … H—N hydrogen bonding of the amide groups and by the CH2OH side chains, forming intersheet hydrogen bonds to the carbonyl oxygens on the next chains (06—H … 07). This gives a structure of parallel poly-N-acetylglucosamine chains with no intersheet hydrogen bonds.

The Ecology of Chitin Degradation

Apparent digestibility of rendered animal protein ingredients for rainbow trout Oncorhynchus / mykiss

Development of high-nutrient-dense, low-pollution diets and prediction of aquaculture wastes using biological approaches

Feather meals and meat and bone meals from different origins as protein sources in rainbow trout (Oncorhynchus mykiss) diets

Effect of extrusion processing and steam pelleting diets on pellet durability, pellet water absorption, and the physiological response of rainbow trout (Salmo gairdneri R.)

C.Y. Cho

Papers

Apparent digestibility of rendered animal protein ingredients for rainbow trout Oncorhynchus / mykiss

Development of high-nutrient-dense, low-pollution diets and prediction of aquaculture wastes using biological approaches

Feather meals and meat and bone meals from different origins as protein sources in rainbow trout (Oncorhynchus mykiss) diets

Effect of extrusion processing and steam pelleting diets on pellet durability, pellet water absorption, and the physiological response of rainbow trout (Salmo gairdneri R.)

Phosphorus utilization by rainbow trout (Oncorhynchus mykiss): estimation of dissolved phosphorus waste output