A Comparative Study of Lipid Composition of an Undervalued Crustacean (Munida spp.) Captured in Winter and Summer

This research was focused on the lipid fraction of an undervalued crustacean (lobster krill; Munida spp.) and the comparative study of individuals captured at winter and summer seasons. For this purpose, seasonal variations were analyzed in the muscle (i.e., tail meat) for proximate composition, lipid class distribution, and fatty acid (FA) profile. Mean total lipids ranged from 0.75 ± 0.08% (summer) to 0.92 ± 0.06% (winter), moisture from 77.94 ± 0.25% (winter) to 78.62 ± 0.38% (summer), and protein from 17.93 ± 0.46% (summer) to 18.22 ± 0.46% (winter). Regarding lipid class content (% of total lipids), phospholipids ranged from 64.85 ± 1.29 (summer) to 67.85 ± 2.56 (winter), sterols from 12.15 ± 0.35 (winter) to 13.54 ± 0.54 (summer), triacylglycerols from 0.04 ± 0.02 (summer) to 1.25 ± 0.88 (winter), and free FA from 1.14 ± 0.72 (winter) to 2.19 ± 0.34 (summer). In both seasons, the most abundant FA were C22:6ω3, C16:0, C18:1ω9, and C20:5ω3. Polyunsaturated fatty acids (PUFA) were found to be the most abundant group in samples from both seasons (50.4–55.3%). Higher PUFA values were determined in summer samples, while a highly valuable ω3/ω6 ratio (from 9.11 ± 1.12 in summer to 10.40 ± 1.39 in winter) was observed. It is concluded that in spite of being a low-fat product, the lipid fraction of this underutilized crustacean can provide highly valuable constituents.     

Fish meal replaced by hydrolysed soybean meal in diets increases growth and improves the antioxidant defense system of silver catfish (Rhamdia quelen)

One of the current challenges of global fish farming is developing plant‐based proteins as a feasible substitute for fishmeal in the formulation of aquafeeds. Substitution levels of fishmeal with hydrolyzed soybean meal (HSM) in diets for silver catfish (Rhamdia quelen) were evaluated for growth, protein metabolism and antioxidant activity. The experiment was carried out in a recirculation system of 20 tanks of 250 L. A total of 300 silver catfish juveniles were used to compose five treatments and four replicates per treatment. Levels of soybean hydrolysate (0%, 5%, 10%, 15% and 20%) were tested in diets (39% protein and 3,500 Kcal) for 60 days. Silver catfish growth was higher at all inclusion levels of HSM when compared to the control diet. No change was shown for body protein deposition. The production of nitrogenous compounds in the liver and muscle was also unaffected by any of the diets. The diet containing 20% HSM promoted an increase in the amounts of non‐protein thiols in the gills and brain. The HSM substitution levels of up to 20% of fishmeal in the diet increases growth and contributes to silver catfish antioxidant activity.     

Soybean expansion impacts on soil organic matter in the eastern region of the Maranhão State (Northeastern Brazil)

Recently, the eastern region of the Maranhão state (Northeastern Brazil) became a hotspot of land-use change (LUC) directly from native vegetation to soybean cultivation, but due to the soil characteristics, LUC has caused substantial soil organic carbon (SOC) and nitrogen depletion. Therefore, we quantified these impacts arising from two factors: (i) different timeframes after LUC and (ii) contrasting soil management practices. For the first study, soil samples (0–30 cm; six replicates) were taken on soybean fields year one, year eight and 15 years after LUC. It the second study, another area was sampled, of which part was managed under no-tillage (NT) and the other using a mouldboard plough (MP). For both studies, native vegetation (NV) was sampled as the control. NV stored about 50 Mg of carbon (C) ha⁻¹; but LUC reduced C stocks by 35% (after 8 and 15 years); moreover, labile-C decreased between 20% and 45%, while, microbial-C decreased between 20% and 60%, considering the interval between year one and 15 years. Regarding soil management, the MP did not cause differences on C stock (24 Mg C ha⁻¹) in comparison to NT; however, both labile-C and microbial-C decreased by 15% to NT, while, decreased by 40% to MP. These results lead us to believe that, since LUC is inevitable, we suggested the adoption of the best agricultural management practices, in order to preserve/increase the SOC, reducing the impacts on GHG emissions and, thus, achieving sustainability and profitability.