Larviculture of the painted river prawn Macrobrachium carcinus in different culture systems

The objective of this study was to evaluate different hatchery systems used for the larviculture of the Macrobrachium carcinus based on survival, larval development and production of post-larvae. The experimental culture was carried out in three phases designated as Phase I (Zoea VI to VIII – Z_{VI – VIII}), Phase II (Zoea VIII to X – Z_{VIII – X}), and Phase III (Zoea X to PL – Z_{X – PL}), with densities of 30, 27.5 and 25 larvae / L, respectively. The M. carcinus larvae (Z_VI) were reared in four culture systems, two being open (Greenwater – GW and Clearwater – CW) and two being closed (Biofloc – BFT and Bio-filter – RAS), distributed in twelve 10 L plastic containers, filled with 20 ppt brackish water, equipped with constant aeration, and water circulated by air lift and heated with thermostat (∼30 °C). The GW treatment was maintained with Chlorophyceae algae in the density of 3–5 × 10⁵ cells/mL. In the CW, the water was previously filtered through a 5 μm mesh screen, sterilized with 10 ppm active chlorine and, dechlorinated with vitamin C and subjected to aeration for 24 h. The BFT received water rich in bioflocs that was matured prior to the experiment and used molasses as a source of organic carbon. In the RAS, the culture water circulated through an external “Dry-Wet” biological filter. The feeding was carried out ad libitum four times daily, alternating a wet diet formula with a commercial diet, which was supplemented with newly hatched Artemia nauplii at a rate of 40–50 per larvae/day. Temperature, dissolved oxygen and pH were monitored daily and the salinity two times per week. Total ammonia, nitrite, nitrate, orthophosphate, alkalinity, total suspended solids, chlorophyll-a, COD and BOD were also analyzed. The best water quality (P < 0.05) was obtained in the RAS, with 0.49 (±0.38), 0.23 (±0.22), and 9.0 (±1.5) mg/L of TAN, NO₂-N and NO₃-N, respectively. In the GW, the nitrogen species showed high fluctuations and higher concentrations at 2.32 (±1.68), 3.53 (±3.53) and 18.2 (±12.9) mg / L of TAN, NO₂-N and NO₃-N, respectively. Considering the three phases (Z_{VI – PL}), the overall survival was 0.03, 1.97, 2.23 and 17.32 % for the BFT, CW, GW and RAS, respectively. When considering the phases separately, the survival in Phase I (Z_{VI – VIII}) was highest in the GW system at 58.7 % while the RAS was the highest in Phases II (Z_{VIII – X}) and III (Z_{X – PL}) at 70.6 % and 60.3 %, respectively. The BFT showed 8.4 (±3.5) PL/L, which was higher (P < 0.05) than that obtained in the RAS (2.8 ± 1.2 PL/L) and the GW (1.3 ± 1.1 PL/L) and similar to that obtained in the CW (5.6 ± 2.0 PL/L). Thus, the larviculture for the M. carcinus may be optimized by adopting a multiphase management strategy, which the intermediate larval stages (Z_{VI – IX}) are reared in the GW system and the final stages (Z_{X – PL}) are reared in the BFT system.     

Improved Cold and Drought Tolerance of Doubled Haploid Maize Plants Selected for Resistance to Prooxidant tert‐Butyl Hydroperoxide

To improve the abiotic stress tolerance of maize (Zea mays L.), doubled haploid (DH) plants were produced by in vitro selection of microspores exposed to tert‐butyl hydroperoxide (t‐BuOOH) as a powerful prooxidant This study investigated the tolerance of the progenies of t‐BuOOH‐selected DH lines to oxidative stress, cold and drought in controlled environment pot experiments by analyses of photosynthetic electron transport and CO₂ assimilation processes, chlorophyll bleaching and lipid peroxidation of leaves. Our results demonstrated that the t‐BuOOH‐selected DH plants exhibited enhanced tolerance not only to oxidative stress‐induced by t‐BuOOH but also to cold and drought stresses. In addition, they showed elevated activities of antioxidant enzymes such as superoxide dismutase, ascorbate peroxidase, catalase, glutathione reductase and glutathione S‐transferase when compared with the DH lines derived from microspores that were not exposed to t‐BuOOH and to the original hybrid plants. The results suggest that the simultaneous up‐regulation of several antioxidant enzymes may contribute to the oxidative and cold stress tolerance of the t‐BuOOH‐selected DH lines, and that the in vitro microspore selection represents a potential way to improve abiotic stress tolerance in maize.     

Setaria digitata was the main cause of equine neurological ataxia in Korea: 50 cases (2015–2016)

This study was performed to examine and clarify the cause of hindlimb ataxia and neuropathy seen in the South Korean horse population. Fifty horses diagnosed with hindlimb ataxia and neuropathy were referred for this study. Neurological examination was performed on 47 horses while necropsy was performed in all 50 animals. The occurrence of neurological diseases increased rapidly in the summer and 47 out of 50 horses were referred after the end of July. The incidence of neurological diseases started from the southern part of Korea in July and proceeded northward in August and September. Although there was no correlation with age, Thoroughbred and Warmblood horses showed a higher incidence rate than Halla and Jeju horses. The incidence rate was 5 times higher in geldings than in mares and stallions. Of the 20 cases, 16 were diagnosed with eosinophilic meningoencephalomyelitis in 2015. The most common lesions observed in 2016 were parasitic meningoencephalomyelitis (10 cases, 33%) and eosinophilic meningomyelitis (7 cases, 23%). Histopathological analysis of the brain and spinal cord revealed nematodes of approximately 100–200 µm in diameter, microcavitation and infiltrates of eosinophils, and brown pigmented macrophage infiltrates. The nematodes were identified as Setaria digitata via DNA sequencing, performed subsequent to polymerase chain reaction using DNA isolated from formalin-fixed paraffin-embedded tissue sections of the spinal cord. These results show that aberrant migration of Setaria digitata larva in the brain and spinal cord was a major cause for neurological signs in horses.     

德州市农业机械化可持续发展的现状与对策

近年来，农机化事业的快速发展，为德州市农业和农村经济的发展发挥了重要作用。但随着农业和农村经济结构的战略性调整，对农机化的发展也提出了新的更高要求。为此，在调查研究的基础上，详细地分析了德州农机化发展的现状及存在的问题，有针对性地提出了加快德州市农业机械化可持续发展的建议与对策。     

Soil N and salinity leaching after the autumn irrigation and its impact on groundwater in Hetao Irrigation District,China

Soil water and salinity are crucial factors influencing crop production in arid regions. An autumn irrigation system employing the application of a large volume of water (2200–2600 m³ ha⁻¹) is being developed in the Hetao Irrigation District of China, since the 1980s with the goal to reduce salinity levels in the root zone and increase the water availability for the following spring crops. However, the autumn irrigation can cause significant quantities of NO₃⁻ to leach from the plant root zone into the groundwater. In this study, we investigated the changes in soil water content, NO₃–N and salinity within a 150 cm deep soil profile in four different types of farmlands: spring wheat (F_W), maize (F_M), spring wheat–maize inter-planting (F_W–M) and sunflower (F_S). Our results showed that (1) salt losses mainly occurred in the upper 60 cm of the soil and in the upper 40 cm for NO₃–N; (2) the highest losses of salt and NO₃–N could be observed in F_W, whereas the lowest losses were found in F_W–M.NO₃–N concentration, pH and electrical conductivity (EC) in the groundwater were also monitored before and after the autumn irrigation. We found that the autumn irrigation caused the groundwater concentration of NO₃–N to increase from 1.73 to 21.6 mg L⁻¹, thereby, exceeding the standards of the World Health Organization (WHO). Our results suggest that extensive development of inter-planting tillage might be a viable measure to reduce groundwater pollution, and that the application of optimized minimum amounts of water and nitrogen to meet realistic yield goals, as well as the timely application of N fertilizers and the use of slow release fertilizers can be viable measures to minimize nitrate leaching.     

Effect of Soaking on Nitrate Concentrations in Teff Hay

Soaking can affect respirable dust particles and the concentrations of some nutrients in alfalfa and cool season grass hays. However, the effect of soaking on nitrates in hay has not been reported. The aim of this study was to evaluate the effects of soaking on teff hay, a warm season annual grass, that contained high concentrations of nitrate (>2.0%). Six bales of teff hay were used for the study. Six 0.5 kg samples were taken from each bale and assigned to one of six soaking treatments: no soaking (control), cold water immersion for 10 seconds, warm water immersion for 10 seconds, cold water soaking for 1 hour, warm water soaking for 1 hour, and cold water soaking for 8 hours. After soaking, hay was dried, ground, and submitted to a commercial laboratory for analysis. Data were analyzed by analysis of variance as a block design. When the main effect of treatment was significant (P < .05), means were separated by Tukey's honest significant difference test. Soaking for 1 or 8 hours decreased water-soluble carbohydrate (P < .0001). Phosphorus, potassium, sodium, and zinc concentrations were reduced by soaking for 1 hour or longer (P, K, Na: P < .0001; Zn: P = .003). Nitrate concentrations were reduced (P < 0.05) to safe levels for horses (≤0.5%) by soaking hay for 1 hour or longer but soaking also reduced the concentrations of some nutrients in the hay. Minimal differences were observed between cold and warm soaking temperatures.     

Response of ammonia oxidizing microbes to the stresses of arsenic and copper in two acidic alfisols

Soil pollution by elevated heavy metals exhibits adverse effects on soil microorganisms. Ammonia oxidizing bacteria and ammonia oxidizing archaea perform ammonia oxidative processes in acidic soils. However, influence of heavy metal stress on soil ammonia oxidizers distribution and diversity is inadequately addressed. This study investigated the responses of ammonia oxidizing bacteria and archaea to heavy metals, Cu and As during short-term laboratory experiment. Two different acidic alfisols named as Rayka and Hangzhou spiked with different concentrations of As, Cu and As + Cu were incubated for 10 weeks. Significant reduction in copy numbers of archaeal-16S rRNA, bacterial-16S rRNA and functional amoA genes was observed along elevated heavy metal concentrations. Ammonia oxidizing archaea was found to be more abundant than ammonia oxidizing bacteria in all the heavy metal treatments. The potential nitrification rate significantly decreased with increasing As and Cu concentrations in the two soils examined. Denaturing gradient gel electrophoresis analysis revealed no apparent community shift for ammonia oxidizing archaea even at higher concentrations of As and Cu. Phylogenetic analysis of archaeal amoA gene from 4 clone libraries indicated that all the archaeal amoA sequences were placed within 3 distinct clusters from soil and sediment group 1.1b of Thaumarchaeota. Our results could be useful for the better understanding of the ecological effects of heavy metals on the abundance and diversity of soil ammonia oxidizers.