Taurine supplementation in fish meal-free diet improved growth, alleviated hypoxic-induced gill injury associating with Ca<sup>2+</sup> homeostasis and endoplasmic reticulum stress in sub-adult grass carp (<i>Ctenopharyngodon idella</i>).
Taurine supplementation at 0.8 g/kg in fish meal-free diets can improve growth and gill health in grass carp under hypoxic conditions.
Where it sits
this study against the rest of the adipotide (prohibitin-tp01) corpusSummary and findings
The study examined the effects of taurine supplementation in fish meal-free diets on growth and gill health in sub-adult grass carp under hypoxic stress. A total of 450 grass carp were divided into six dietary groups, including a control and five taurine-supplemented groups. The optimal taurine level for growth and gill health was found to be between 0.8 and 1.04 g/kg.
Abstract
Taurine is a multifunctional feed additive that is abundant in fish meal but scarce in plant protein sources. The aim of this study was to investigate the effects of taurine supplementation in fish meal-free diet on sub-adult grass carp (<i>Ctenopharyngodon idella</i>) growth performance and gill health under hypoxic stress, and the possible mechanisms. A total of 450 grass carp (697.75 ± 0.99 g) were randomly distributed into six dietary groups in triplicate of 25 fish. The dietary treatments were as follows: a fish meal diet (FM group), and five fish meal-free diets supplemented with 0, 0.4, 0.8, 1.2, or 1.6 g/kg taurine (NFT 0, NFT 0.4, NFT 0.8, NFT 1.2, and NFT 1.6 groups, respectively). The growth experiment lasted for 60 d. After that, a 96-h hypoxia experiment was conducted. Based on the average final weight per treatment, 24 healthy grass carp were selected from each group, equally divided into normoxia and hypoxia subgroups in triplicate of 4 fish for respective normoxic (dissolved oxygen ≥ 6 mg/L) and hypoxic treatments (dissolved oxygen 1.0 mg/L). The results showed that compared with FM group, the growth performance (final body weight, weight gain, percentage weight gain, and specific growth rate) in NFT 0 group was inhibited (<i>P</i> < 0.05), but in NFT 0.8 group was comparable (<i>P</i> > 0.05). Moreover, dietary taurine can effectively alleviate hypoxia-induced gill morphology damage. Hypoxia resulted in a significant increase in the Ca<sup>2+</sup> content in gill tissues (<i>P</i> < 0.001). Under hypoxia, compared with FM group, both the activity of Ca<sup>2+</sup>-ATPase and the expression levels of SERCA2, CAM, and CAMKⅡ in NFT 0 group were decreased (<i>P</i> < 0.05), but there was no significant difference as compared with NFT 0.8 group (<i>P</i> > 0.05), while they were increased by adding 0.8 g/kg taurine to the fish meal-free diet (<i>P</i> < 0.05). Meanwhile, supplementing 0.8 g/kg taurine in the fish meal-free diet reduced the expression levels of <i>grp78</i>, <i>perk</i>, <i>ire1</i>, and <i>atf6</i> (<i>P</i> < 0.05), thereby further alleviating endoplasmic reticulum stress. The results showed that adding 0.8 g/kg taurine to the fish meal-free diet was the most effective in improving the growth performance of grass carp and alleviating the injury of grass carp gills under hypoxic stress. Quadratic regression analysis revealed that, with percent weight gain and reactive oxygen species content in gill tissue after hypoxic stress as indicators, the optimal dietary inclusion level of taurine in fish meal-free diets was determined to be 1.04 and 0.78 g/kg.
Background
This study addresses the challenge of maintaining growth and health in fish raised on plant-based diets, which lack taurine, a key component of fish meal. Taurine is known for its role in growth and stress response in aquatic species. Understanding its effects on growth and gill health under hypoxic conditions is crucial for optimizing aquaculture practices.
Methods
The study involved 450 sub-adult grass carp divided into six groups, including a fish meal control and five fish meal-free diets with varying taurine levels (0 to 1.6 g/kg). The growth experiment lasted 60 days, followed by a 96-hour hypoxia test. Primary outcomes included growth performance metrics and gill health indicators under normoxic and hypoxic conditions.
Results
The NFT 0 group showed inhibited growth compared to the FM group (P < 0.05), while the NFT 0.8 group showed comparable growth (P > 0.05). Taurine at 0.8 g/kg alleviated hypoxia-induced gill damage and improved Ca2+ homeostasis and endoplasmic reticulum stress markers (P < 0.05). Quadratic regression suggested optimal taurine levels of 1.04 and 0.78 g/kg for weight gain and reactive oxygen species reduction, respectively.
Interpretation
The study suggests that taurine supplementation at 0.8 g/kg can effectively replace fish meal in diets for grass carp, improving growth and gill health under hypoxic stress. While statistically significant, the clinical relevance is limited to aquaculture settings. The findings align with previous studies on taurine's role in stress response but require validation in broader contexts.
Key findings
- 450 grass carp (697.75 ± 0.99 g) were studied.
- Growth performance in NFT 0 group was inhibited (P < 0.05).
- NFT 0.8 group showed comparable growth to FM group (P > 0.05).
- 0.8 g/kg taurine reduced gill damage under hypoxia (P < 0.05).
- Optimal taurine level determined as 1.04 and 0.78 g/kg.
Limitations
- Study conducted on fish, limiting generalizability.
- Specific to hypoxic stress conditions.
- Short 60-day growth period.
- Single species focus.