Abstract
The present study intended to evaluate the effects of early introduction of inert diet in lipid digestibility and metabolism of sole, while larval feed intake, growth and survival were also monitored. Solea senegalensis larvae were reared on a standard live feed regime (ST) and co-feeding regime with inert diet (Art R). Trials using sole larvae fed with Artemia enriched with two different lipid emulsions, containing glycerol tri [1- 14C] oleate (TAG) and L-3-phosphatidylcholine-1,2-di-[1- 14C] oleoyl (PL), were performed at 9 and 17 days after hatching (DAH) to study lipid utilization. Co-feeding did not affect sole survival rates (ST 59.1 ± 15.9%; Art R 69.56 ± 9.3%), but was reflected in significantly smaller final weight at 16 DAH (ST 0.71 ± 0.20; Art R 0.48 ± 0.14 mg). Higher feed intake was observed in sole larvae fed on Artemia enriched with labeled PL at 9 DAH but not at 17 DAH. At 17 DAH, the smaller larvae (Art R treatment) ingested proportionally more Artemia in weight percentage, independently of enrichment. At 9 DAH lipid digestibility was equal among treatments and higher than 90%, while at 17 DAH it was higher in ST treatment (around 73%) compared to the Art R group (around 66%). Lipid retention efficiency at 9 DAH was higher in the Art R treatment, reaching values of 50%, while these values almost duplicated at 17 DAH, ranging up to 80% in both treatments without significant differences. These results show that co-feeding of live feed and inert diet from first-feeding in Senegalese sole has a toll in terms of growth and lipid digestibility but does not seem to compromise lipid metabolic utilization.
Highlights
These results show that co-feeding of live feed and inert diet from first-feeding in Senegalese sole has a toll in terms of growth and lipid digestibility but does not seem to compromise lipid metabolic utilization
In order to successfully achieve the objective of a significant partial replacement of live feed by inert diets from first feeding, a detailed understanding of the larval digestive physiology and how it may be influenced by the dietary components is indispensable (e.g., Cahu and Zambonino Infante, 2001; Morais, 2005; Engrola, 2008)
The handling to transfer the larvae with the Pasteur pipette was a methodology that has been previously used in other study (Engrola et al, 2009b), in which it was observed that the larvae were actively feeding on Artemia in the incubation vials and, it is believed that this factor did not affect the results, regarding the stress caused to larvae
Summary
In order to successfully achieve the objective of a significant partial replacement of live feed by inert diets from first feeding, a detailed understanding of the larval digestive physiology and how it may be influenced by the dietary components is indispensable (e.g., Cahu and Zambonino Infante, 2001; Morais, 2005; Engrola, 2008).The Senegalese sole (Solea senegalensis, Kaup 1858) is a flatfish found along the Mediterranean and Atlantic coasts, and is a promising candidate for aquaculture in Europe since the nineties due to good market prices (Howell, 1997; Dinis et al, 1999; Imsland et al, 2003). In order to successfully achieve the objective of a significant partial replacement of live feed by inert diets from first feeding, a detailed understanding of the larval digestive physiology and how it may be influenced by the dietary components is indispensable (e.g., Cahu and Zambonino Infante, 2001; Morais, 2005; Engrola, 2008). Weaning success of Senegalese sole is still a critical step, with two strategies being possible: sudden weaning and weaning in co-feeding with Artemia metanauplii (Engrola et al, 2007). In spite of recent progress in sole larvae nutritional requirements and understanding of larval digestive physiology, weaning results obtained so far are variable and difficult to reproduce (Conceição et al, 2007b). It has been demonstrated that protein digestibility and retention are depressed by co-feeding with high levels of Artemia replacement by inert diet, and thereby lead to lower growth (Engrola, 2008)
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