Addition of hydrolysed porcine mucosa to low-fishmeal feed improves intestinal morphology and the expressions of intestinal amino acids and small peptide transporters in hybrid groupers (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂)

Abstract

Aquaculture routinely uses fishmeal (FM) as feed, but its increasing cost has prompted the search for alternative protein sources. This study conducted an 8-week feeding trial to evaluate the effects of adding hydrolysed porcine mucosa (HPM) to low-FM feed on the growth performance, intestinal morphology, and expressions of intestinal amino acids and small peptide transporters in hybrid groupers (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂, initial weight 7.51 ± 0.03 g). Five iso-nitrogenous and isolipidic experimental diets were formulated containing HPM in proportions of 0% (Group HPM0), 3% (HPM3), 6% (HPM6), 9% (HPM9) and 12% (HPM12). Specific growth and weight gain rates were significantly lower in fish fed >6% HPM (P < 0.05). Catalase and glutamic oxaloacetic transaminase activities were significantly higher in Group HPM12 than in Group HPM0 (P < 0.05). In the distal intestine (DI), Group HPM6 had significantly higher villus length than Group HPM3, and significantly higher muscle thickness than Groups HPM0, HPM3 and HPM12 (P < 0.05). The alpha diversity index of intestinal microbiota was not significantly affected by HPM content (P > 0.05). Expressions of LAAT1 in the proximal intestine (PI), CAT2, SNAT3 and EAAT1 in the mid intestine (MI) and CAT2, B0AT3 and EAAT1 in the DI were highest in Group HPM3 (P < 0.05). Expressions of CAT1, CAT2, SNAT3 and EAAT1 in the PI, CAT1, PAT1, B0AT2 and B0AT3 in the MI, and PAT1 and SNAT3 in the DI were highest in Group HPM6 (P < 0.05). The expressions of PepT1 of the MI and DI were significantly higher in Groups HPM9 and HPM12 than in others (P < 0.05). The results show that adding 3% or 6% HPM to feed can improve DI morphology and increase intestinal amino acid transporter expression without reducing growth performance. Dietary supplementation with 12% HPM may improve antioxidant capacity and expression of small peptide transporters but may also cause liver damage and reduce growth performance. Therefore, HPM is a promising alternative to FM for use in aquaculture feeds.