No abstract

Iso-nitrogenous and iso-lipidic diets containing 0%, 3%, 6%, 9%, and 12% hydrolyzed porcine mucosa (namely, HPM0, HPM3, HPM6, HPM9, and HPM12) were prepared to evaluate their effects on the growth performance, muscle nutrition composition, texture property, and gene expression related to muscle growth of hybrid groupers ( Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂). Groupers were fed to apparent satiation at 08:00 and 16:00 every day for a total of 56 days. It was found that the weight gain percentage in the HPM0, HPM3, and HPM6 groups did not differ ( P > 0.05). The cooking loss and drip loss of the dorsal muscle in the HPM3 group were lower than those in the HPM6 and HPM9 groups ( P < 0.05). The hardness and chewiness of the dorsal muscle in the HPM3 group were higher than those in the HPM0, HPM9, and HPM12 groups ( P < 0.05). The gumminess in the HPM3 group was higher than that in the HPM9 and HPM12 groups ( P < 0.05). The total essential amino acid content of the dorsal muscle in the HPM12 group was higher than that in the HPM0 group ( P < 0.05). The contents of total n-3 polyunsaturated fatty acid and total n-3 highly unsaturated fatty acid, as well as the ratio of n-3/n-6 polyunsaturated fatty acid in the dorsal muscle was higher in the HPM0 group than in all other groups ( P < 0.05). The relative expressions of gene myogenic factor 5, myocyte enhancer factor 2c, myocyte enhancer factor 2a, myosin heavy chain, transforming growth factor-beta 1 ( TGF - β1 ), and follistatin ( FST ) were the highest in the dorsal muscle of the HPM3 group. The results indicated that the growth performance of hybrid grouper fed a diet with 6% HPM and 27% fish meal was as good as that of the HPM0 group. When fish ingested a diet containing 3% HPM, the expression of genes TGF-β1 and FST involved in muscle growth were upregulated, and then the muscle quality related to hardness and chewiness were improved. An appropriate amount of HPM could be better used in grouper feed.

In this study, five iso-nitrogenous and iso-lipidic experimental low-FM diets were formulated with enzyme-digested hydrolysed porcine mucosa (EH) at concentrations of 0 g/kg (EH0, controls), 30 g/kg (EH3), 60 g/kg (EH6), 90 g/kg (EH9) and 120 g/kg (EH12). Juvenile hybrid groupers (n = 450; initial body weight 7.50 ± 0.02 g) were randomly divided into 15 tanks and fed the experimental diets twice daily for 56 days. The weight gain rate, specific growth rate, protein efficiency rate, feed conversion rate and feed intake rate of group EH3 were not significantly different from those of controls. The villus length and muscle thickness of the distal intestine (DI) in group EH12 and the villus width of the proximal intestine (PI) in group EH6 were significantly higher than those in controls. The Shannon index was significantly higher in group EH6 than in other groups. Group EH6 exhibited 17 pathway subclasses with significant differences to the other groups, comprising organismal systems (4), human diseases (6), cellular processes (2), metabolism (4) and environmental information processing (1). The expressions of CAT1, CAT2, LAAT1 and SNAT3 in the PI, and PAT1, B 0 AT3 and B0, +AT in the mid intestine (MI), and EAAT1 and PepT1 in the PI and MI in group EH6 were significantly higher than those in controls. The expressions of CAT1, CAT2, LAAT1, PAT1, SNAT3, EAAT1, B 0, + AT and PepT1 in the DI of group EH3 were significantly greater than those in controls. The maximum amount of EH that could be added to low-FM feed to improve the digestive enzyme activity and amino acid and small peptide transport ability of the DI without obviously affecting the growth performance of hybrid groupers was 30 g/kg. EH contents ≥ 60 g/kg had negative impacts on growth performance and feed efficiency.

BackgroundAt present, fish meal (FM) resources are in short supply, and competition for food between humans and animals is becoming increasingly critical. Finding non-grain protein sources that can replace FM is the key to solving the rapid development of aquaculture.MethodsSeven trial diets were prepared with 0 g/kg (EP0), 30 g/kg (EP3), 60 g/kg (EP6), 90 g/kg (EP9), 120 g/kg (EP12), 150 g/kg (EP15), and 180 g/kg (EP18) of enzyme-digested poultry by-product meal (EPBM) by replacing of FM. A total of 630 hybrid groupers (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂) were equally portioned into 21 tanks. At 8:00 and 16:00 each day, groupers were fed until they were full for a cumulative period of 8 weeks.ResultsThe results showed that 30 g/kg of EPBM significantly increased the rates of weight gain and special growth (P &lt; 0.05). Significantly higher activities of serum glutamic pyruvic transaminase, glutamic oxaloacetic transaminase, catalase, and superoxide dismutase were observed in the EP3 group (P &lt; 0.05). The categories and numbers of the top 10 dominant bacteria in the phylum and genus levels were not significantly influenced by feed (P &gt; 0.05). In the proximal intestine and distal intestine, there were significantly higher expressions of SNAT3, LAAT1, CAT2, and CAT1 in the EP3 group compared with the EP0 group (P &lt; 0.05). In the EP3 group, the expressions of PepT1, LAAT1, B0, +AT, and CAT2 were significantly increased in MI than those in all other groups (except the EP0 group, P &lt; 0.05).ConclusionWhen FM was replaced by 30 g/kg of EPBM, growth performance, antioxidant capacity, and the ability to transport amino acids and peptides of hybrid grouper were significantly improved.