Development and evaluation of microparticulate diets for early weaning of Atlantic cod Gadus morhua larvae

Abstract

Early weaning trials were conducted with cod larvae to investigate the effectiveness of microparticulate diets (microbound and microcoated) with and without lipid‐walled capsules (LWCs). The microparticulate diets were evaluated by measuring physical parameters of the diet in the water column (leaching and settling rate), palatability (intestinal fullness), performance of the diet (survival and growth), and examination of the diet in the larval intestine (histological analysis). A feeding trial was conducted using four experimental diets (carrageenan microbound diet, carrageenan microbound diet with LWCs, zein microcoated diet and zein microcoated diet with LWC), one commercial diet (BioKyowa: A‐250) and a live feed control (rotifers and Artemia). Survival of cod larvae to 39 days post‐hatch ranged from 5 to 10% with the experimental diets, 22.9% with the BioKyowa diet, and 36.5% with live prey. There was evidence of food absorption with all diets in the form of lipid vacuoles in the midgut and supranuclear vacuoles in the hindgut. Large vacuoles in the midgut were more abundant in the enterocytes of larvae fed the experimental diets compared with larvae on the BioKyowa diet and the live feed control. Based on observations of intestinal fullness, the experimental diets appeared to be less palatable than the BioKyowa diet. As a result, it took longer to wean the larvae and higher mortality was experienced during weaning. Once successfully weaned, the experimental diets yielded growth rates equivalent to larvae feeding on the commercial diet for the remainder of the experiment.

Early weaning of yellowtail amberjack Seriola lalandi dorsalis (Gill 1863) larvae

“…In many fish species, early weaning of fish larvae may reduce the quality of fish, and skeletal malformations have been frequently reported in this process [3,5]. The cause of skeletal malformations in early weaning larvae may be due to the malnutrition supply to fish larvae and early cannibalisms (mechanical damage) during the weaning process [2,18,19].…”

“…In practice, weaning of most temperate marine fish species such as Trachinotus ovatus and Seriola lalandi are usually commenced after metamorphosis [1,2]. Previous studies have demonstrated that early introduction of micro-particles diets to marine fish larvae can have positive effects on fish adapting to the micro-particles diets [3,4]. But premature introduction of the micro-particles diets can also inhibit fish growth and survival as fish cannot digest the artificial diets when their digestive system is not properly developed [2,5,6].…”

Degradation of amino acids by leaching in feeds for shrimp

“…The amino acid leaching in water has been evaluated in several studies (Lopez-Alvarado et al 1994;Baskerville-Bridges & Kling, 2000;Yufera et al 2002;Onal & Langdon, 2004), these researchers observed that leaching can be extensive and there are major differences between types of food and between different components.…”

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“…The development of microdiets for larval marine fish, such as the Pacific bluefin tuna (Thunnus orientalis) (Haga et al, 2010(Haga et al, , 2011Takeuchi & Haga, 2015), red sea bream (Pagrus major) (López-Alvarado & Kanazawa, 1994a;Teshima, Koshio, Ishikawa, Alam & Hernadez, 2004), olive flounder (Bai, Cha & Wang, 2001;Takeuchi et al, 2003;Wang et al, 2004;Ji et al, 2013), gilthead seabream (Sparus aurata) (Saleh et al, 2013), European sea bass (Dicentrachus labrax) (Person-Le Ruyet, Alexandre, Thebaud & Mugnier, 1993) and Atlantic cod (Gadus morhua) (Baskerville-Bridges & Kling, 2000;Johnson, Cook, Nicklason & Rust, 2009) have been successfully made. Especially, Takeuchi et al (2003) reported that a mixture of microparticle diets containing two different molecular weight peptides (1000-2000 and 30,000 Da) was a good source of protein and this type of diet can be given to olive flounder from the larval to juvenile stage.…”

“…The possibility of the complete replacement live food with microdiet alone for some marine fish larvae seems to be limited (Baskerville-Bridges & Kling, 2000;Takeuchi et al, 2003;Wang et al, 2004;Faulk & Holt, 2009;Tang, Chen & Wu, 2010;Alam et al, 2013;Li et al, 2013), but the combination of microdiet with live food effectively improved the survival and growth of the larval stages of marine fish (Kolkovski, Koven & Tandler, 1997;Yúfera et al, 2000;Teshima et al, 2004;Ji et al, 2013). Teshima et al (2004), in particular, showed that live food (Rotifer and Artemia) could be completely replaced with a zein-microbound diets containing a molecular weight of 1000 and 3000 Da soybean peptides or with the combined half amount of zein-microbound diet containing a molecular weight of 1000 Da soybean peptides and live food for 30 days after hatching (DAH) in red sea bream larvae; however, for 15 DAH olive flounder larvae, the combined half amount of zein-microbound diet containing a molecular weight of 1000 Da soybean peptide and live food only.…”