Effects of Dietary Soy Protein Concentrate on Growth, Digestive Enzymes Activities and Target of Rapamycin Signaling Pathway Regulation in Juvenile Soft-Shelled Turtle, <i>Pelodiscus sinensis</i>

Abstract

Soft-shelled turtle, Pelodiscus sinensis is important aquatic species in China, and searching for alternatives protein resources to fish meal (FM)-based feeds in feed has become urgent and important for its sustainability development. The present study was conducted to assess the effects of dietary soy protein concentrate (SPC) on growth, digestive enzymes and target of rapamycin (TOR) signaling pathway of juvenile P. sinensis (4.56 ± 0.09 g). SPC was applied to replace FM protein at 0%, 15%, 30% and 60% (designated as T0, T15, T30 and T60, respectively), and each diet was fed to triplicate groups. The results showed that there was no significant difference in growth performance and feed utilization except of the turtles fed with T60 diet, of which showed poorer daily weight gain and feed conversion rate. The pepsin/trypsin and Na + -K + ATP-ase activities decreased dramatically when SPC level increased, and lipase activities in liver and intestinal tract also showed decline tendency. However, amylase activities were unaffected. No significant differences were observed in TOR, S6K1 and 4E-BP1 genes mRNA expression level of TOR signaling pathway among the treatments. However, the relative phosphorylated level of these proteins decreased significantly when SPC level increased. The present study indicated that high SPC substitution level would suppress digestive enzymes and TOR signaling pathway proteins phosphorylated level and eventually result in growth reduction of P. sinensis.

Aquaculture Impacts on China’s Marine Wild Fisheries Over the Past 30 Years

“…The trophic level of fish also decreased from 4.5 in 1985 to 3.77 in 2014, and that of other species also decreased from 3.00 in 1985 to 2.31 in 2014 (Tang et al, 2016). Increased knowledge on the digestive processes and nutritional requirements of farmed species and on the processing of raw material combined with the use of alternative proteins has led to impressive reductions in fishmeal inclusions in aquafeeds and rise in feed conversion ratios in cultured species in China (Zhou et al, 2015;Han et al, 2018). Moreover, the cultured species that previously only feed on low-valued fish/trash fish, for example, large yellow croaker, can also feed on compound aquafeeds, and the proportion of aquafeeds is continuously increasing (Li et al, 2013(Li et al, , 2021Zhang et al, 2016).…”