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- Co-feeding of inert diet from mouth opening does not impair protein utilization by Senegalese sole (Solea senegalensis) larvaePublication . Engrola, S.; Mai, M.; Dinis, Maria Teresa; Conceição, L. E. C.In most marine species inert diets alone have a poor ability to sustain fish larvae growth and development. Furthermore, results of co-feeding inert diets and live prey are variable, which may be related to the effect of inert diets on digestive maturation and subsequently protein utilization. The aim of the present work was to investigate how different feeding regimes, live feed alone or co-fed with an inert diet, influence protein utilization in Senegalese sole larvae. Feed intake, protein absorption, protein retention and protein catabolism were estimated in sole from 8 to 35 days after hatching (DAH), using 14C-labelled Artemia protein and posterior incubation in metabolic chambers. Postlarvae that were co-fed with an inert diet from mouth opening ate more than postlarvae fed Artemia alone at most sampling ages. Sole Artemia protein digestibility ranged from 56.97 (16 DAH) to 81.32% (22 DAH). Sole larvae that were fed a second meal had a slightly, though significant, higher digestibility than sole fed a single meal. Digestibility was lower in co-fed sole during metamorphosis climax, and similar between treatments at other developmental stages. Retention efficiency remained almost constant during early development, and was not affected by feeding regime. In short, co-feeding of an inert diet from mouth opening does not impair protein utilization by Senegalese sole larvae.
- Senegalese sole larvae growth and protein utilization is depressed when co-fed high levels of inert diet and Artemia since first feedingPublication . Engrola, S.; Dinis, Maria Teresa; Conceição, L. E. C.A large effort has been dedicated in the past years to the development of nutritional balanced inert diets for marine fish larvae in order to suppress the nutritional deficiencies of live feed. In this study growth performance, Artemia intake, protein digestibility and protein retention were measured for Senegalese sole (Solea senegalensis Kaup), in order to provide insight into how protein utilization affects growth performance. Three feeding regimes were tested: ST – standard live feed; ArtRL – live feed and 20%Artemia replacement with inert diet (dry matter basis) from mouth opening; ArtRH – live feed and 58%Artemia replacement with inert diet from mouth opening. Artemia intake and protein metabolism were determined at 6, 15 and 21 days after hatching using 14C-labelled Artemia protein and subsequent incubation in metabolic chambers. At the end of the experiment, sole fed exclusively with live feed were significantly larger than sole from Artemia replacement treatments. Protein digestibility decreased during sole ontogeny, and more sharply in ArtRH sole. Concomitantly retention efficiency increased during ontogeny but with a slight delay in ArtRH sole. Senegalese sole larvae growth and protein utilization is depressed when co-fed high levels of inert diet and Artemia, mostly during metamorphosis climax.
- Co-feeding of live feed and inert diet from first-feeding affects Artemia lipid digestibility and retention in Senegalese sole (Solea senegalensis) larvaePublication . Mai, M.; Engrola, S.; Morais, S.; Portella, M. C.; Verani, J. R.; Dinis, Maria Teresa; Conceição, L. E. C.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.