Tributyrin enhances growth and intestinal health in green mud crab (Scylla paramamosain) through butyrate-driven metabolic regulation

Tributyrin (TB), a derivative of butyric acid, is considered a promising feed supplement to regulate growth and intestinal barrier function in livestock and aquatic animals. However, its application in the green mud crab (<i>Scylla paramamosain</i>) has not been extensively investigated. Therefore, this study aimed to investigate the regulatory mechanism of TB on growth performance, intestinal barrier function, butyrate metabolism, digestive enzyme activity, and carbohydrate-lipid metabolism in the green mud crab. A total of 144 crabs (10.68 ± 0.03 g) were divided into four groups with three replicates of 12 crabs each and hand-fed either a basal diet (Con) or diets containing 0.05%, 0.10%, and 0.20% TB for nine weeks. Results revealed that compared with Con, supplementation with 0.20% TB significantly promoted growth performance in the green mud crab (<i>P</i> < 0.05), including final body weight and percent weight gain. Additionally, TB supplementation significantly improved intestinal health by upregulating the mRNA relative expression of intestinal physical-barrier genes, including <i>zo-1</i> (<i>P</i> = 0.031), <i>pt-1</i> (<i>P</i> = 0.010), <i>pt-44</i> (<i>P</i> < 0.001), <i>mlck</i> (<i>P</i> = 0.033), and claudin (<i>P</i> = 0.006) and reducing diamine oxidase (DAO) activity (<i>P</i> = 0.001); TB supplementation also enhanced lipase activity in the stomach, lipase, amylase, and protease activities in the hepatopancreas, and lipase and protease activities in the intestine (<i>P</i> < 0.05); TB supplementation significantly activated butyrate metabolism, including upregulation of <i>hadh</i> (<i>P</i> = 0.001) and <i>acads</i> (<i>P</i> = 0.006) mRNA relative expression, and downregulation of <i>acadl</i> (<i>P</i> = 0.001) mRNA relative expression, increased adenosine triphosphate (ATP) (<i>P</i> = 0.002) contents and nicotinamide adenine dinucleotide reduced/nicotinamide adenine dinucleotide⁺ (NADH/NAD⁺) (<i>P</i> < 0.001) downregulated transcriptional expression related to glycolysis (<i>pygl</i>, <i>gk</i>, <i>pfk</i>, <i>hk</i>, and <i>pk</i>), and upregulated mRNA relative expression related to gluconeogenesis (<i>gys</i>, <i>g6pase</i>, <i>pdh</i>, <i>pc</i>, and <i>pepck</i>) (<i>P</i> < 0.05); furthermore, TB induced lipid deposition in the hepatopancreas by upregulating lipid synthesis genes (<i>fas</i>, <i>6pgd</i>, <i>g6pd</i>, and <i>acc</i>) at the transcriptional level and increasing the area of lipid droplets in hepatopancreas tubules (<i>P</i> = 0.001). Overall, current results indicated that TB could enhance growth in the green mud crab through coordinated improvements in digestive enzyme activity, intestinal health, and tissue-specific metabolic regulation.