Growth Performance, Digestive Enzymes, and TOR Signaling Pathway of Litopenaeus vannamei Are Not Significantly Affected by Dietary Protein Hydrolysates in Practical Conditions.

Jianchun Shao,Xinwei Liu,Wei Zhao,Lei Wang

doi:10.3389/fphys.2018.00998

Abstract

Protein hydrolysates have been widely reported as the protein source of aquatic feed. However, previous studies on protein hydrolysates focused on fish under experimental conditions. In this study, a 6-week feeding trial in a greenhouse was conducted to investigate the effects of partially replacing fishmeal by protein hydrolysates on growth performance, digestive enzymes, and TOR signaling pathway of Litopenaeus vannamei under practical conditions. This involved randomly selecting 72,000 shrimps (initial body weight 2.26 ± 0.02 g) and placing them in groups inside nine concrete tanks (L 5 m × W 5 m × H 1 m) (3 treatments × 3 replicates × 8000 individuals per concrete tank). Two isonitrogenous (430 g kg-1) and isolipidic (80 g kg-1) diets were prepared: fishmeal diet (FM) containing 400g kg-1 fishmeal, and protein hydrolysates diet (PH) in which 15% of the fishmeal was replaced by protein hydrolysates. A commercial diet (CD) was used as reference. The final weight (FW), percent weight gain (PWG), specific growth ratio (SGR), and total weight for each tank (TW) of L. vannamei fed with FM and PH diets were not significantly different (P > 0.05). However, shrimp fed with PH diet had significantly higher FW, PWG, SGR, and TW values than those fed with CD diet (P < 0.05). Trypsin activity was significantly lower in shrimp fed with CD diet, than in shrimp fed with FM and PH diets (P < 0.05). However, trypsin activity of L. vannamei fed with FM and PH diets were not significantly different (P > 0.05). The mRNA expression of tor, s6k, and 4e-bp genes were not significantly affected between FM and PH diets, while tor and s6k expression levels of CD diet were significantly down-regulated. Based on the above data, 15% replacement of fishmeal with protein hydrolysates did not make any difference on shrimps compared with FM group. Therefore, protein hydrolysates can partially replace fishmeal as the protein source of shrimp formula feed in practical conditions.

Highlights

The white shrimp, Litopenaeus vannamei, is a commercially important species and widely cultured in farms in the western hemisphere
Shrimp fed with protein hydrolysates diet (PH) diet had significantly higher final weight (FW), percent weight gain (PWG), specific growth ratio (SGR), and TW values than those fed with commercial diet (CD) diet (P < 0.05)
Our results showed that no significant differences in growth performance, including FW, PWG, SGR, feed efficiency (FE), and TW, were detected among the fishmeal diet (FM) and PH groups

Summary

Introduction

The white shrimp, Litopenaeus vannamei, is a commercially important species and widely cultured in farms in the western hemisphere It has become the most extensively cultured crustacean species in China due to its high nutritional value, short life cycle, and high survival rate and yield, since its introduction in 1988 (Zhao et al, 2018). The combination of high nutritional value and increasing market demands have stimulated the development of an industry focused on the production of shrimp-formulated feed (Zhao et al, 2007). With rapid developments in aquaculture industry, the use of fishmeal as a major protein source in formulated feed has increased the demand and prices for this product. The results of Sun et al (2016) indicated that 50% of fishmeal can be replaced by fermented cottonseed meal without adverse effects on the growth and feed utilization of L. vannamei

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Conclusion