Abstract
The effect of hydrolyzed fish protein powder (HFP) on the growth, intestinal development, gene mRNA expression, and enzyme activity in the intestine and liver of juvenile hybrid grouper (Epinephelus fuscoguttatus ♀ and Epinephelus lanceolatus ♂) was assessed after an 8-week feeding trial. Seven isonitrogenous (50%) and isolipidic (9%) diets were fed to hybrid grouper with 0% (CT), 1% (H1), 1.5% (H2), 2% (H3), 2.5% (H4), 3% (H5), and 4% (H6) HFP. No significant difference (p > 0.05) in weight gain rate (WGR), specific growth rate (SGR), feed conversion ratio (FCR), and survival rate (SR) was observed in all the groups. The crude protein content in the H6 group was significantly higher than in the other groups (p < 0.05). Intestinal lipase and trypsin activity were significantly higher in H3 and H5 groups (p < 0.05). In the serum, superoxide dismutase (SOD) activity was significantly higher in H5 and H6 groups, while malondialdehyde (MDA) activity was lower (p < 0.05) compared to other treatments. Insulin-like growth factor (IGF-I) and target of rapamycin (TOR) mRNA expression levels in the intestine and muscle were significantly higher in the H2 group and H1 group (p < 0.05), respectively. The most abundant intestinal bacteria found at the genus level are Acinetobacter, Vibrio, and Flavobacteriaceae. The villus was significantly longer in hybrid grouper fed with different levels of HFP compared to the control, and fish in the H2 group had thicker intestinal muscle compared to the other groups (p < 0.05). In conclusion, the addition of HFP to the low fishmeal (FM) diets of juvenile grouper improved the intestinal development and increased the levels of intestinal digestive enzymes.
Highlights
Aquaculture is anticipated to fulfill the global request for aquatic animals due to the reduction in capture fisheries since the 1990s (FAO, 2020)
This study aims to evaluate the effect of hydrolyzed fish protein powder (HFP) on the growth, survival, whole-body composition, serum and liver physiological and biochemical indexes, intestinal morphology, digestive enzymes, gene mRNA expression, and intestinal microbiota in juvenile hybrid grouper
The hybrid grouper did not have a significant difference in weight gain rate (WGR), specific growth rate (SGR), feed conversion ratio (FCR), survival rate (SR), and viscerosomatic index (VSI) (p > 0.05) in all groups
Summary
Aquaculture is anticipated to fulfill the global request for aquatic animals due to the reduction in capture fisheries since the 1990s (FAO, 2020). In aquaculture practice, feed accounts for over 50% of production cost, which is mainly composed of protein (Tacon and Metian, 2008). The most preferred dietary source of protein, which is the most expensive and important nutrient influencing fish growth and feed cost, especially in carnivorous fish, is obtained from FM due to its high digestibility, well-balanced amino acid, and rich source of essential n-3 fatty acids (Tacon and Metian, 2008; Olsen and Hasan, 2012). Processing fish produces a substantial amount of waste, which includes skin/scales, bones, swim bladders, roes, intestines, blood, and liver, representing about 57% of total weight. Large portions of these by-products, which contain a large amount of bioactiverich materials, are wasted, discarded, or underutilized (Meeker, 2009; Kumar et al, 2018). Quality protein in animal by-products can be hydrolyzed to obtain small molecular peptides which can act as a flavoring and good source of amino acids (Choi et al, 2012; Kumar et al, 2012)
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