No abstract

The goal of this study was to optimize the mixture of swine manure (SM) and cattle manure (CM) used in the vermicomposting process, seeking to increase the manure biodegradation rate and enhance the biomass production of both earthworms and higher plants. To achieve this goal, physico-chemical parameters were determined to assess the final compost quality after 50 days of vermicomposting. The different manure ratios used to produce the composts (C) were as follows (SM:CM, % m/m basis): C1 100:0, C2 (75:25), C3 (50:50), C4 (25:75), and C5 (0:100). In addition, the earthworm biomass and the phytoproductivity of lettuce (Lactuca sativa L.) plants grown in mixtures (1:1) of natural soil and the most viable vermicomposts were investigated. The C1 and C2 compost compositions were associated with high earthworm mortality rates. The C3 compost provided the highest mineral concentrations and C5 showed the highest lettuce yield (wet biomass). The results verify that stabilized cattle manure is an excellent substrate for the vermicomposting process and that fresh swine manure must be mixed with pre-stabilized cattle manure to ensure an optimized vermicomposting process, which must be controlled in terms of temperature and ammonia levels. It is concluded that small livestock farmers could add value to swine manure by applying the vermicomposting process, without the need for high investments and with a minimal requirement for management of the biodegradation process. These are important technical aspects to be considered when circular economy principles are applied to small farms.

This work aimed to assess the effect of the probiotic strain, Lactobacillus plantarum, on the levels of leptin, IGF-1 and their receptors on the hepatopancreatic tissues of Nile tilapia (Oreochromis niloticus) and then correlate fish growth performance and gut microbiological parameters. Fish juveniles (±23g) were reared in a recirculation system with constant aeration and temperature (25°C). They were distributed into six polyethylene tanks (45L) and fed twice a day at 5% of the tank biomass with the respective diets: control (commercial diet without probiotic) and supplemented with L. plantarum inoculum (1 x 108 CFU mL-1), both in triplicate. After 30 days of feeding, L. plantarum-fed fishes showed greater weekly growth rate, final weight, and feed conversion rate, in addition to higher count of lactic-acid bacteria and lower count of pathogenic bacteria in the intestinal tract, when compared to the control group. The immunostaining intensity for IGF-1 and leptin hormones was lower after L. plantarum supplementation than in the control group, with no change in the level for receptors. This reduction could implicate important changes in fish metabolism and homeostasis.