ⅠIntroduction
1. The considerable risks of oxidative stress and loosing profits among aquaculture
Risk of oxidative stress: During aquaculture, various stressors like changes in weather, worsening water quality, higher breeding density, unstable feed quality, overfeeding and improper transportation, can affect aquatic animal’s health, leading to produce more free radicals that can cause oxidative damage to internal organs.
Risk of loosing profits: Oxidative damage causes an increased mortality rate during the aquaculture(indicated by less market quantity) and a decline in commodity performance (indicated by poor vitality), which consequently leads to lose profits in aquaculture.
2. How to addressing the issues of oxidative stress among aquaculture?
Studies have demonstrated that exogenous antioxidant ingredients can alleviate oxidative stress, such as micro elements Vc, Ve, carotenoids, glutathione, taurine, zinc and selenium, and antioxidant peptides including Glu-Tyr, Ala-Phe etc. (Xiao, 2019)
3. How to effectively select antioxidant ingredients in aquafeed?
Definitely having antioxidant capacity:
Ingredients being detected and measurable.
Having clear and effective antioxidant pathway:
The principle of antioxidant being validated.
Not affected by conditions of using:
The activity being not affected by processing technique and digestive environment in vivo.
Repetitively verification of antioxidant efficacy during breeding:
Antioxidant efficacy being verified under different breeding conditions.
Enzyme-treated Functional Protein of Mytech is designed to enhance the health of aquatic animal and promote utilization of protein, containing 20% bioactive peptides with strong antioxidant and anti-inflammatory properties. This functional protein has shown stable efficacy in several aqua feeds (largemouth bass, yellow catfish, Litopenaeus Vannamei, channel catfish, etc.). In production, it has shown to strengthen liver and intestinal health, and to enhance antioxidant capacity and growth in aquatic animal.
Molecular content of enzyme-treated functional protein and effects for feed processing
【Data source】Mytech R&D Center
【Gratitude】The research, carried out by Pro. Jiang’s team, Sichuan Agricultural University, focus on Enzyme-treated Soy Protein (ETSP) of Mytech replacing fish meal and the excessive oxytetracycline (OTC) as stressor to assess the effect on repairing oxidative liver damage of largemouth bass.
Ⅱ Purpose
The aim of this experiment is to investigate the impact of enzyme-treated functional protein on repairing oxidative liver damage of largemouth bass after replacing fish meal. Additionally, this research explores the application value of using enzyme-treated cottonseed protein and provides valuable insights in largemouth bass feed as a solution to maintain liver and intestine health, and to enhance anti-stress capacity.
Ⅲ Protocol
1. Place
Assessment of production performance: Experiment Station of Ya’an, Sichuan Agricultural University, China
Determination of biochemistry indexes: Sichuan Agricultural University, Chengdu, China
2. Materials
Species: largemouth bass
Stage and periods: fed the control diet or ETSP diet for 13 weeks(initial weight 22g), then transferred into tanks containing 240 mg/L OTC breeding for 2 weeks.
Water quality parameters as follows: outdoor concrete tanks, water temperature at 23-27℃, dissolved oxygen content about 6 mg/L and PH 7.0-7.5.
3. Methods
Groups: totally in 3 groups, each group with 3 replicas, each replica with 36 largemouth basses
Diet design: 4% ETSP replacing fish meal
4. Indicators
Observation of liver tissues’ structure, analysis of enzymatic activity, level of protein expression and detection of mitochondrial membrane potential, etc.
Ⅳ Results
1. ETSP repairing structural liver damage caused by OTC
Liver tissues in the OTC group showed severe damages: hepatomegaly, discoloration, cytolysis, necrosis, and nuclear pyknosis of cells, more mitochondrial crest fractures, swelling, membrane rupture, and phagocytic vesicles.
Liver tissues in the OTC + ETSP group showed partial repair: the liver appeared brownish red and soft, with clearly defined boundaries for each lobule, a normal and compact arrangement of liver cells as well as clear boundaries and regular blood sinusoids, and the cell nucleus being normally round or oval, with intact inner and outer nuclear membranes, clear nucleoli, uniform distribution of nuclear chromatin.
2. ETSP mitigating liver oxidation caused by OTC
The contents of ROS and MDA were remarkably elevated after OTC exposure, while the activities of T-SOD,CAT, GST and AHR decreased.
ETSP reduced, even eliminated the oxidative damages caused by OTC, while the activities of T-SOD, GST, CAT and AHR increased.
3. ETSP protecting and repairing the antioxidant mechanism damaged by OTC
OTC induces the oxidative liver damages by disturbing the enzyme antioxidant system of MAPK/Nrf2, activating the mitochondrial depolarization via PINK1/Parkin signaling pathway(down-regulation of mitochondrial fusion-related protein(OPA1) and up-regulation of mitochondrial division-related protein(DRP1) ).
Ⅴ Application value
Aquatic animals: improve liver health and enhance anti-stress capacity.
Feed industry: promote better feed quality, while reducing formula cost.
We have using enzyme-treated functional protein to investigate enhancing the anti-stress capacity of aquatic animals in several species, including Litopenaeus Vannamei(resisting high salinity, low PH and long transportation), sturgeon(poor water quality caused by flood), yellow catfish(resisting leaving water and high ammonia nitrogen), turtle(anti-inflammation). These species all have achieved good application results.