L. calcarifer may be fed with several types of feeds, viz. trash fish, pressed pellets and high-energy, extruded pellets. The advantages and disadvantages of these feeds are summarized in Table 6. barramundi is reluctant to feed from the water surface or off the bottom. Under Australian pond culture conditions farmers prefer to use floating/slow-sinking extruded pellets (Glencross, 2006) and under cage culture conditions a pressed sinking pellet is equally effective (Musa et al., 1999). Recent improvements in feed use efficiency more than fully offset the higher production costs when using high energy pelleted feeds (Glencross et al., 2003). However, the use of high energy (lipid) feeds can lead to significant increases in body lipid content (Williams et al. 2003a).

FCRs usually range from 1 to 1.5:1 with dry pellets. An extensive review of feeding trials can be found in Tucker et al. (2005). When using trashfish, FCRs range between 4 and 8:1 (Kungvankij et al., 1985).

Animal protein sources:

Fish meal is widely used in barramundi feeds and can support good growth at inclusion levels of up to 60 percent. Meat meals have also been successfully used at inclusion levels of 40 percent. Organoleptic characteristics of the flesh have been studied and fish that had been fed diets with a high meat meal content obtained high scores for overall liking from the panellists (Williams et al., 2003b). Microbound diets for larvae using squid meal powder were found to have a significantly high nutritional value and digestibility than fish meal based microdiets (Nankervis and Southgate, 2006a).

Plant protein sources:

Plant proteins can partially replace fish meal (Table 7). Several cereals have been tested and solvent extracted soybean meal (SBM) was shown to support good growth at a 10 percent fishmeal protein replacement level (Tantikitti et al., 2005). Williams (1998) did not observe palatability problem with SBM up to a 30 percent inclusion level. Solvent extracted SBM is more palatable than extruded or steamed full fat SBM (Boonyaratpalin et al., 1998). Coloso et al. (1996) obtained good weight gain and FCR (1.7:1) in fish fed with a combination of fishmeal, shrimp head meal, scrap squid meal, SBM, and kangkong leaf meal as protein sources. Ipil-ipil leaf meal can also be used but this may result in a lower FCR. White cowpea and green mung bean meals have been used as protein sources in practical diets at inclusion levels of 18 percent of the diet without affecting growth (Eusebio and Coloso, 2000). Corn gluten meal can be included at up to 10 percent of the diet (Pongmaneerat and Boonyaratpalin, 1995).

Lipid sources:

Raso and Anderson (2002) have shown that fish oil can be replaced with soybean oil with no effect on growth because of its appropriate ω3:ω6 ratio. Similarly, Anderson and Raso (2003) reported that partial replacement of fish oils with vegetable oils (soybean, canola and linseed) has no significant effect of the lipid, moisture and protein content of the fish carcass.

Carbohydrate sources:

Several cereals can also be blended with the feed as a carbohydrate source but McMeniman (2003) observed that increased gelatinization of starch led to decreasing energy digestibility.

According to Smith (2001), the major ingredients used in barramundi feeds are (percent as used): fish meal (40 percent), feed grade cereals (30 percent), meat meal (10 percent), soybean meal (10 percent), fish oil (5 percent) and others (5 percent). Examples of practical feed formulations are given in Table 8 and Table 13 and specifications of commercial feeds are listed in Table 10.

Several amino acids have attractant properties (Kolkovski, 2000) and their use in microdiets contributes to weaning efficiency (Curnow et al., 2006). Kanazawa et al. (1984) have successfully used an amino acid mixture, presented in Table 11b, as a feeding stimulant. A growth promoter (Barramundi IGF-I) has been developed but is presently only used for research purposes (Table 11a). Vitamins and minerals should be added to the feed and examples of premix compositions are given in Tables 12 and 13.

Feeding rates and frequencies for intensive barramundi culture are presented in Table 14a and details of reported feeding methods in cage culture are given in Table 14b. Williams and Barlow (1999) suggested that there was no benefit in feeding small fish (40 g) more than twice daily, and large fish (>270 g) more than once a day.

Harpaz et al. (2005a) have shown that the feeding time had almost no affect on fish growth. The fish consumed food whenever it was fed, even during the night.

During the weaning process feeding time and place should be fixed, and the fish should be attracted by sound to induce them to school to improve the feeding response (Kungvankij et al., 1985).

Barramundi show compensatory growth after moderate feed restriction (50–75 percent satiation for 2 weeks; Qin and Tian, 2004).