Pike-perch larvae growth in response to administration of lactobacilli-enriched inert feed during first feeding

Abstract

This study evaluated whether inert feed enriched with Lb. paracasei subsp. paracasei BGHN14 may be used as a weaning diet for first feeding pike-perch larvae. Three experimental groups were weaned from the start of exogenous feeding: two groups were given inert feed enriched with BGHN14 either via 12 h incubation with live BGHN14 cells or via coating with homogenized BGHN14 cells and one group was supplemented non-enriched inert feed. In all three groups Artemia was co-fed with inert feed during weaning. Control group larvae were fed Artemia exclusively during the treatment period. Treatment lasted fourteen days, starting from the 6th day post-hatch (DPH). Larval sampling was performed on the 20th DPH for gene expression and enzyme activity analysis. Larvae were also sampled on the 32nd DPH for morphometric and body composition analysis. Our results showed that weaning of first feeding pike-perch larvae was associated with an increase of fish condition (0.72 ± 0.12–0.77 ± 0.11 versus 0.67 ± 0.11 in controls), but it suppressed skeleton development, according to Col1 mRNA expression (1 ± 0.51–1.06 ± 0.36 versus 2.07 ± 0.53 in controls) and reduced fat deposition (1.25 ± 0.23–1.49 ± 0.33 versus 1.84 ± 0.31% in controls). This presumably reflected lower availability of soluble proteins in microdiet as opposed to live food, along with high leaching rate of amino acids from solid feed particles, as reported in our previous studies. However, skeleton differentiation was not impaired in group weaned on BGHN14 homogenate coated feed (Col1 mRNA expression: 2.68 ± 0.72), which was enriched in skeleton building and taste stimulating amino acids. These larvae were also presented with substantially higher length (15.28 ± 2.55 versus 13.93 ± 2.31 mm in controls) and weight (26.56 ± 13.83 versus 21.03 ± 11.25 mg in controls), which correlated with lower trypsin activity (1.06 ± 0.13 versus 1.43 ± 0.26 mU/mg of proteins in controls) and an increase of PLA2 to trypsin activity ratio (453.12 ± 109.36 versus 264.84 ± 69.03 in controls). Present study suggests that weaning of first feeding pike-perch larvae using BGHN14 homogenate coated microdiet supports skeleton development and improves fish growth.