Incidence of systemic granulomatosis is modulated by the feeding sequence and type of enrichment in meagre (Argyrosomus regius) larvae

Abstract

Systemic granulomatosis is the most frequent disease in juvenile and adult meagre, but studies regarding the first appearance of granulomas in larvae do not exist. In order to evaluate this, meagre larvae were fed four different feeding regimes as follows: RS and RO (rotifer enriched with Easy DHA Selco or Ori-Green from 3 to 30 dph respectively), RAS and RAO (rotifer enriched with Easy DHA Selco or Ori-Green from 3 to 21 dph and Artemia enriched with Easy DHA Selco or Ori-Green from 12 to 30 dph respectively). All treatments were also fed with commercial microdiet from 20 to 30 dph. At 30 dph weight, length, specific growth rate and survival were significantly higher in Artemia-fed larvae, regardless of the enrichment.Microscopic first appearance of granulomas was observed in 20 dph larvae fed RS and RO. At 30 dph granulomas and thiobarbituric acid reactive substances (TBARS), values were significantly higher in RS and RO-fed larvae than in RAS and RAO-fed larvae. The results showed that granulomas first appeared in meagre larvae at 20 dph when fed rotifers only. Conversely, a reduced appearance of granulomas and lipid peroxidation occurs when Artemia is included in the feeding sequence reinforcing the hypothesis of a nutritional origin of the systemic granulomatosis. K E Y W O R D SArtemia, feeding sequence, meagre larvae, rotifer, systemic granulomatosis, vitamin E

Appearance of systemic granulomatosis is modulated by the dietary supplementation of vitamin E and C in meagre (Argyrosomus regius) larvae fed inert microdiets

“…It has previously been shown that the co-feeding with rotifer and Artemia enriched with Easy DHA Selco prior to eating an inert commercial microdiet prevented the appearance of granulomas in meagre larvae (Ruiz et al, 2018b). Consistently, no granulomas were observed at 30 dph in the present trial after following the same feeding sequencing and enrichment protocol what seems to reinforce the role of nutrition as the main trigger in the appearance of systemic granulomatosis.…”

“…The substitution of fish oil by krill oil was enough to the correct growth of meagre larvae but increased the percentage of granulomas and the peroxidation index. Therefore, it has been demonstrated in the present and previous studies (Ruiz et al, 2018b) that systemic granulomatosis can be completely mitigated in meagre larvae by controlling feeding sequence as well as levels of antioxidant nutrients.…”

“…It must be noted that the prevalence of systemic granulomatosis is so high in adult meagre that it can affect almost 100 % of population (Ghittino et al, 2004), being this stage too late to try to avoid the appearance of the disease. Nevertheless, granulomas have not only been detected in adult fish, but meagre larvae have also been found to show this histological alteration at very early stages (Ruiz et al, 2018b). In the afore mentioned study, granulomas were first described in liver and kidney at 20 days post hatching (dph) albeit differences were found among larvae fed the different dietary treatments/feeding sequences.…”

“…Artemia was enriched with Easy DHA Selco (0.6 g million Artemia -1 ) for 24 h before being fed to the larvae. Meagre larvae were fed with enriched Artemia from 12 to 30 dph following the protocol established by Ruiz et al, (2018b). Before each feeding, Artemia were counted and added to maintained at a density of 1.3-1.5 Artemia L -1 in the experimental tanks.…”

“…The overall aim of the present study was to evaluate the role of vitamin E and C in the appearance of systemic granulomatosis in weaned larvae (30 dph). Prior to the start of the study larvae were co-fed with rotifer and Artemia enriched with Easy DHA Selco as larvae fed this dietary regime did not show any granulomas at 30 dph in a previous trial (Ruiz et al, 2018b). Following this feeding sequence meagre will be fed four microdiets formulated to contain graded levels of inclusion of vitamin E and C. Additionally a fifth diet was formulated to contain krill oil as the single lipid source.…”