Effect of dietary betaine on growth, physiological response, and immune-related genes in Chinese mitten crab (Eriocheir sinensis)

Abstract

A 2-month study investigated the effects of dietary betaine on growth, physiological response, and immune-related genes in Chinese Mitten Crab (Eriocheir sinensis). A total of 160 crabs, averaging 43.35 ± 0.05 g, were randomly assigned to 16 cement pools, with four pools per treatment and ten crabs per pool. Experimental diets included a control (no betaine) and betaine supplements at 0.5, 1.0, and 1.5 g/kg, respectively. From the results, crabs fed 1 g/kg betaine had higher final weight (FW), specific growth rate (SGR), feed intake (FI), and meat yield (MY), with lower FCR than the control. No significant differences were observed with the 1.5 g/kg supplement. Dietary treatment did not affect Alanine aminotransferase enzyme (ALT), total cholesterol (TC), triglycerides (TG), or non-esterified fatty acids (NEFA). However, aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) activities were significantly reduced in crabs fed betaine, with the lowest levels in those fed 1 and 1.5 g/kg in hemolymph and hepatopancreas. Superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) activities in the hepatopancreas were significantly higher than in the control, with opposite trends in malondialdehyde (MDA) content, but no differences were observed in crabs fed 1 g/kg. Crabs fed 1 and 1.5 g/kg betaine had higher lysosomes in the hepatopancreas than the control. Similar results were observed in hemolymph. alf1 was upregulated with increasing betaine, peaking in crabs fed 1.5 g/kg, but showed no difference at 1 g/kg. alf2 increased with betaine, then decreased at higher levels, with no significant difference between the 0.5 g/kg and the control. Lastly, alf3 and crus1 were significantly upregulated in crabs fed betaine compared to the control. This study suggests that dietary betaine supplementation at the level of 1 g/kg is the most effective.