Coprophagy prevention alters microbiome, metabolism, neurochemistry, and cognitive behavior in a small mammal

Abstract

Many small mammals engage in coprophagy, or the behavior of consuming feces, as a means to meet nutritional requirements when feeding on low-quality foods. In addition to nutritional benefits, coprophagy may also help herbivores retain necessary gut microbial diversity and function, which may have downstream physiological effects, such as maintaining energy balance and cognitive function. Here, we used collars to prevent Brandt's vole (Lasiopodomys brandtii) from engaging in coprophagy and monitored changes in microbial community structure, energy metabolism, and cognitive performance. In this research, we found that coprophagy prevention decreased alpha diversity of the gut microbiota, and altered proportions of microbial taxa such as Bacteroidetes, Firmicutes, and Oscillospira. Preventing coprophagy resulted in a reduced body mass, and increased food intake. Importantly, coprophagy prevention decreased vole cognitive behavior and altered levels of neurotransmitters in brain. Daily acetate administration was able to reverse some of the coprophagy prevention-induced changes in microbiota composition, metabolism, neurochemistry, and cognitive behavior. These findings identify the functional importance of coprophagy behavior and interactions between the gut microbiota, energy metabolism, and neurological function. Our results suggest that coprophagy contributes to stabilizing the gut microbiota, promoting microbial metabolism, maintaining host energy balance and, consequently, altering cognitive performance.

Fig. 1. Coprophagy affected the gut microbiota (Experiment 1).

a Alpha diversity (Faith’s phylogenetic diversity) of bacterial communities across groups (n = 8 per group, one-way ANOVA). b NMDS plot based on weighted and unweighted UniFrac distance metrics depicting the differences in fecal microbial community structure in different groups. c Relative abundances of bacterial phyla over the course of Experiment 1. d Predicted functional categories that differed significantly in relative abundance between 0 week and 2 weeks. Data are means ± SEM (n = 8 per group), and bars that do not share the same letter are significantly different from one another based on the Student–Newman–Keuls method.

Fig. 2. Coprophagy prevention induces alterations in metabolic phenotypes in voles (Experiment 2).

a Changes of body mass over the length of the experiment. b Changes of food intake over the length of the experiment (repeated measures ANOVA). c Resting metabolic rates (RMR) of treatment groups. d Cost of non-shivering thermogenesis (NST) of treatment groups. e Concentration of T3 in serum. f Moving distance in three groups in the open-field test. g Differences among three groups in cecum mass. h Small intestinal villus length. i The total mass of feces recovered per day at the end of the experiment. j The total caloric content of recovered feces per day. k, l The concentrations of six short-chain fatty acids (SCFAs) in cecum contents. Con: control group, coprophagy, CP: coprophagy prevention, SCP: coprophagy with a sham collar. Data are presented as means ± SEM (n = 6 per group), and bars that do not share the same letter are significantly different from one another based on the Student–Newman–Keuls method.

Fig. 3. Coprophagy prevention induces alterations in cognitive performance and neurodevelopment in voles (Experiment 2).

a The duration and distance in the “food arm” during the Y-maze test. b The total moving distance of three groups in the Y-maze test. c The concentration of neurotransmitters in hypothalamus. d The concentration of neurotransmitters in the hippocampus. e, f Expression of tyrosine hydroxylase (TH) in hypothalamus and hippocampus. g, h Expression of arginine vasopressin (AVP) in the hypothalamus and hippocampus. Con: control group, coprophagy, CP: coprophagy prevention, SCP: copropghay with a sham collar. Data are presented as means ± SEM (n = 6 per group), and bars that do not share the same letter are significantly different from one another based on the Student–Newman–Keuls method.

Fig. 4. Effects of acetate supplementation on host physiology and gut microbiota during coprophagy prevention (Experiment 3).

a Changes of body mass over the length of the experiment. b Changes of food intake over the length of the experiment (repeated measures ANOVA). c Colon lengths of the three treatment groups. d, e The concentrations of six short-chain fatty acids (SCFAs) in cecal contents. f Ghrelin concentration in the serum. g Expression of FFAR2 in the hippocampus. h Expression of neuropeptides in hypothalamus.(POMC, CART, NPY, AgRP). i NMDS plot based on weighted and unweighted UniFrac distance metrics representing the differences in fecal microbial community structure in different groups. j Relative abundances of microbial phyla across treatment groups. CON: control group, coprophagy, CP-PBS: coprophagy prevention with PBS gavage, CP-Ace: copropghay prevention with Acetate gavage. Data are means ± SEM (n = 7 per group), and bars that do not share the same letter are significantly different from one another based on the Student–Newman–Keuls method.

Fig. 5. Supplementation of acetate can promote the cognitive performance and development of hippocampal neurons during coprophagy prevention (Experiment 3).

a The moving distance in the “food arm” during the Y-maze test. b The proportion of time and distance in the “food arm” during the Y-maze test. c The proportion of investigations of the familiar and novel objects. d The proportion of residence time with familiar and novel objects. e The time spent in close pursuit of conspecifics. f The frequency of investigation of conspecifics. g The expression of neuropeptides in the hippocampus. CON: control group, coprophagy, CP-PBS: coprophagy prevention with PBS gavage, CP-Ace: copropghay prevention with acetate gavage. Data are means ± SEM (n = 7 per group), and bars that do not share the same letter are significantly different from one another based on the Student–Newman–Keuls method.