Dietary Cerium (Ammonium Ceric Nitrate) Promoted the Growth, Intestinal Digestive Enzyme Activity, and Positive Modulation of Intestinal Microbiota of Largemouth Bass (<i>Micropterus salmoides</i>).

Abstract

This study investigated the dietary effects of cerium (ammonium ceric nitrate, Ce (NH₄)₂(NO₃)₆) on the growth, serum antioxidant, intestinal digestive enzyme activity, tissue morphology and microbiota of <i>Micropterus salmoides</i>. Seven diets were designed with cerium supplementation of 0 (CON), 10 (Ce10), 20 (Ce20), 40 (Ce40), 60 (Ce60), 80 (Ce80) and 120 mg/kg (Ce120), respectively. Largemouth bass juveniles (initial weight of 16.89 ± 0.04 g) were fed with the above diets for 56 days. Compared with the control group, the weight gain of the Ce40 group increased by 14.4% and the feed conversion ratio decreased by 0.13 (<i>p</i> < 0.05). The Ce60, Ce80 and Ce120 groups showed significantly higher superoxide dismutase activity and lower malondialdehyde concentration compared with the control group (<i>p</i> < 0.05). Protease activity in the Ce20 and Ce40 groups and amylase activity in the Ce40 group were markedly elevated relative to the control group (<i>p</i> < 0.05). The proportion of Firmicutes was increased and the proportion of Proteobacteria was decreased by the addition of 10 mg/kg and 40 mg/kg Ce (Ce10 and Ce40 groups). In summary, dietary cerium supplementation can promote the growth, intestinal digestive enzyme activity, and positive modulation of the intestinal microbial flora of juvenile <i>Micropterus salmoides</i>. Based on the second-order polynomial regression analysis of WG or the FCR, the appropriate inclusion level of dietary cerium for juvenile largemouth bass was estimated to be 57.9 and 60.0 mg/kg, respectively.