Pectin from dry cacao pod husk mediates growth performance, immune resistance responses and carbohydrate metabolism of Litopenaeus vannamei through dietary administration

Abstract

The sustainable uses of cacao, Theobroma cacao L, pod husk (CPH) produced from cacao bean industry bring environment great benefits. Botanical polysaccharides possessing a variety of physiological functions are therefore referred to as biological response modifiers, and those are also found in CPH. In this study, the weight gain rate (WGR), length gain rate (LGR), feeding efficiency (FE), and survival rate (SR) of shrimp, Litopenaeus vannamei, fed diets containing CPH pectin at 0 (CON), 1.0 (CPH1), 3.0 (CPH3) and 6.0 (CPH6) g/kg were calculated every 7 days within 56 days of feeding. The non-specific immune parameters, disease resistance, tolerance to hypothermal stress and stress indicators were also evaluated after the shrimp fed with CPH pectin containing diets. Shrimp that were fed with CPH3 after 56 days had higher WGR, LGR, and FE than those in CPH0. The SR significantly increased for shrimp challenged with Vibrio alginolyticus, and subjected to hypothermal (14 °C) stress when they were fed diets containing CPH3 and CPH6, and CPH6 after 14 or 28 days of feeding, respectively. Dietary CPH3 and/or CPH6 showed a significant increase of total hemocyte count (THC), differential hemocyte count (DHC), phenoloxidase (PO) activity, respiratory bursts (RBs), and phagocytic activity and clearance efficiency to V. alginolyticus at 14 and/or 28 days. Furthermore, shrimp fed with CPH pectin-contained diets after 14 and 28 days retarded secretion of dopamine (DA) and norepinephrine (NE), and decreased the level of glucose and lactate in plasma under cold stress. We therefore recommend that CPH pectin can be used as a physiomodulator for shrimp by dietary administration at 3.0 g/kg for 56 days to promote growth; and at 3.0–6.0 g/kg within an appropriate time frame (28 days) to regulate neuroendocrine and immune responses, and carbohydrate metabolism lead to enhance resistance against pathogen and hypothermal stress.