Jie Wang, Yanxian Li, Alexander Jaramillo-Torres
et al.
Abstract Background The importance of the gut microbiota for physiological processes in mammals is well established, but the knowledge of their functional roles in fish is still limited. The aims of this study were to investigate associations between variation in taxonomical composition of the gut microbiota and gut health status in Atlantic salmon and to explore possible modulatory effects of dietary prebiotics in one net-pen farm in open water. The fish with initial mean body weight of around 240 g were fed diets based on the same basal composition, either without (Ref diet) or with (Test diet) yeast cell wall based-prebiotics, during the marine production phase from December to September the following year. Sampling was conducted at three sampling time points: January, April, and September, with average water temperature of 3.9 ℃, 3.4 ℃ and 9.6 ℃, respectively. Results As the fish progressed towards September, growth, brush border membrane enzyme activities, and the expression in the gut of most of the observed genes involved in immune (e.g., il8, cd4a, myd88, il1b, gilt, tgfb, cd8b and cd3), barrier (e.g., zo1, occludin, ecad, claudin25b and claudin15), and metabolism increased significantly. Lipid accumulation in pyloric enterocytes decreased remarkably, suggesting improvement of gut health condition. The growth of the fish did not differ between dietary treatments. Further, dietary prebiotics affected the gut health only marginally regardless of duration of administration. Regarding gut microbiota composition, a decrease in alpha diversity (Observed species, Pielou and Shannon) over time was observed, which was significantly associated with an increase in the relative abundance of genus Mycoplasma and decrease in 32 different taxa in genus level including lactic acid bacteria (LAB), such as Lactobacillus, Leuconostoc, and Lactococcus. This indicates that developmental stage of Atlantic salmon is a determinant for microbial composition. Multivariate association analysis revealed that the relative abundance of Mycoplasma was positively correlated with gut barrier gene expression, negatively correlated with plasma glucose levels, and that its relative abundance slightly increased by exposure to prebiotics. Furthermore, certain LAB (e.g., Leuconostoc), belonging to the core microbiota, showed a negative development with time, and significant associations with plasma nutrients levels (e.g., triglyceride and cholesterol) and gene expression related to gut immune and barrier function. Conclusions As Atlantic salmon grew older under large-scale, commercial farm settings, the Mycoplasma became more prominent with a concomitant decline in LAB. Mycoplasma abundance correlated positively with time and gut barrier genes, while LAB abundance negatively correlated to time. Dietary prebiotics affected gut health status only marginally.
Abstract The purpose of this article is to determine the energy input per m³ in Norwegian forestry in the years 1948/49 and 1978/79 and to find operational methods that require little energy. The energy for production of 1 unit of each of the means of production in forestry has been computed. For food, fodder and clothes, only the increase of energy use in forest work has been taken into account. For all the other means of production, the total consumption for each operation in forestry has been taken into account. The energy input has been computed on that base. The energy input has declined from 105 kWh/m³ i.b. (inside bark) in 1948/49 to 96 kWh/m³ i.b. in 1978/79. The long distance transport required about 55 percent of the energy in both periods. Felling with chain saw required 5.8 kWh/m³ i.b., felling with handtools 18 kWh/m³ i.b., and felling with tree processors 38 kWh/m³ i.b. Tree-length terrain transport with agricultural tractors required 19.4 kWh/m³ km i.b., forwarders 53.9 kWh/m³ km i.b., and cable crane 139.4 kWh/m³ km i.b. Long distance transport with railroad in 1978/79 required 0.23 kWh/m³ km i.b., and trucks in 1978/79 required 0.73 kWh/m³ km i.b. Forest Sci. 29:300-304.