Administration of host‐derived probiotics does not affect utilization of soybean meal enriched diets in juvenile turbot (Scophthalmus maximus)

Abstract

In today's aquaculture, the cost‐intensive and scarce fishmeal is increasingly replaced by plant‐based feedstuff such as soybean meal (SBM). However, SBM contains saponins which can have adverse effects on fish's digestive tract potentially culminating in severe enteritis. In a 60 day feeding trial we studied the use of autochthonous bacteria as probiotics upon SBM supplementation on juvenile turbot. Growth performance, feed conversion, body composition and health status were assessed for five different treatment groups, comprising a fishmeal control (FM ctrl), a SBM control without probiotics (SBM ctrl) and three multi‐species probiotic treatments. For the production of the probiotic treatments a basal diet with a composition identical to the SBM ctrl including 40% SBM of total dry matter likewise was prepared. The basal diet was stepwise top coated with three different probiotic supplementations: (a) three distinct isolates with saponin‐metabolizing ability (SBM + degrad); (b) three distinct isolates inhibitory towards the pathogen, Tenacibaculum maritimum (SBM + anta); and (c) a commercial probiotic application (SBM + com). Individual weight gain was highest in FM ctrl but only SBM + degrad diet showed a significantly lower value (p < 0.05). The feed conversion ratio was lowest in FM ctrl and significantly higher in SBM + degrad (p < 0.01). The protein retention efficiency did only differ significantly between FM ctrl and SBM + degrad (p < 0.05), whereas lipid retention efficiency remained unaffected. Whole body composition and gross energy content were similar in all treatments lacking significant differences. The condition factor was significantly elevated in SBM + degrad compared to FM ctrl (p < 0.05). Hematocrit was highest in FM ctrl and significantly lower in the other treatments (p < 0.01) with SBM + com accounting for the lowest value (p < 0.001). The hepatosomatic index was slightly increased in FM ctrl but no significant difference was detected. Regarding the spleen somatic index SBM + anta treatment revealed the highest and SBM ctrl a significantly lower value (p < 0.05). In conclusion, the growth performance of fish did not benefit from the different probiotic treatments, while body composition and gross energy content remained at an appropriate level. Moreover, the overall health status was on a sufficient level in all treatments which confirms the high dietary tolerability of our putative probiotic isolates by the fish.

Sustainable fish feeds: potential of emerging protein sources in diets for juvenile turbot (Scophthalmus maximus) in RAS

“…Even though the condition factor (CF) of turbot from the PLANT group showed statistically a difference to the control and PAP group (2.07 vs. 2.11 and 2.10, respectively), the physiological relevance is minor and does not indicate poorer nutritional status. CFs above 2 indicate an overall good nutritional status of the fish, as presented CFs are similar to values of in previous studies (Fuchs et al 2015;Nagel et al 2017;von Danwitz et al 2016;Wanka et al 2019;Weiß and Buck 2017). In previous studies, a reduced CF was observed in turbot fed with plant-based diets (Bonaldo et al 2015) and insect meal-based diets (Kroeckel et al 2012) at a substitution/replacement level of more than 55%.…”

“…Interestingly, it has been shown that the reduction and replacement of fishmeal with alternative feed ingredients could lead to contradicting results. Decreasing fishmeal content may lead to a decreased HSI (Bai et al 2019;Gu et al 2017;Kroeckel et al 2012;von Danwitz et al 2016;Wanka et al 2019), unchanged HSI (Bonaldo et al 2015;Fuchs et al 2015;Wang et al 2016;Weiß and Buck 2017) or even increased HSI (Dietz et al 2012;Fournier et al 2004;Nagel et al 2017). This aspect might be worth investigating in more detail to unravel the observed variation in HSI, hepatic glycogen and lipid dependent on alternative feed ingredients.…”

Effects of dietary plant and animal protein sources and replacement levels on growth and feed performance and nutritional status of market-sized turbot (Scophthalmus maximus) in RAS

“…At final sampling, the condition factor (CF) of the individually tagged fish from the PAP60 (1.9) group was significantly lower compared to the fish from the CTRL group (2.0). The difference is very small and the CFs presented in the fish from all groups is considered as normal (Fuchs et al, 2015;von Danwitz et al, 2016;Nagel et al, 2017;Weiß and Buck, 2017;Wanka et al, 2019), whereas turbot strains from France appear to have a lower CF (Imsland et al, 2000;Arfsten et al, 2010). In smaller turbot the CF was reduced at FM replacement levels of 45% by fermented soybean and blood meal in turbot (Dan et al, 2021;Zheng et al, 2022) more than 55% with plantbased diets (Bonaldo et al, 2015) and insect meal-based diets (Kroeckel et al, 2012).…”

Probiotics in Fish Nutrition—Long-Standing Household Remedy or Native Nutraceuticals?

“…Previous findings indicate that the use of multistrain probiotics improves functionality and efficacy. Provided that mutual inhibition can be excluded, the combination of multiple beneficial isolates is recommended [75][76][77].…”