The effect of temperature on the development of yolk‐sac larvae of European hake (Merluccius merluccius L.) under laboratory conditions

The effect of temperature (10, 13, 16, 19 and 22°C) on hatching, development and survival of yolk‐sac larvae of European hake, Merluccius merluccius, was studied. At 22°C the experiment was suspended because all eggs died a few hours after incubation. Five morphological indicators of larval development (standard length – SL, yolk‐sac volume – YSV, oil globule diameter – OD, body height – BH and body wet weight – BW) were analysed. SL, YSV, OD and BW of newly hatched larvae were biggest in size and weight at low temperatures (P < 0.05). Throughout the experiments, the rates of changes in SL, YSV and OD varied with temperature (P < 0.05). By contrast, BH and BW remained constant and did not show significant relationship with the effect of temperature (P > 0.05). The potential model showed that the SL growth rate varied from 0.05 to 0.08 mm day^?1 from 10.5 to 19.5°C respectively. However, at all temperatures two growth phases were identified: a rapid growth phase followed by a slow one. Rapid growth rate in length and depletion in yolk‐sac and oil globule occurred at high temperatures. After total YSV and OD consumption (death by starvation), larvae died between 8 and 14 days at 19.5 and 10.5°C respectively, reaching a maximum length of 4.3 mm at 10.5°C. Metabolic indices such as: lowest threshold temperature (T₀); effective larval development (); cumulative thermal units (TC) to complete larval development; the temperature coefficient on growth rate in length (Q₁₀) and the condition factor (K) were also studied.     

Growout production of camouflage grouper, Epinephelus polyphekadion (Bleeker), in a tank culture system

Growout production of the camouflage grouper, Epinephelus polyphekadion (Bleeker), in a 10-m³-capacity fibreglass tank culture system was evaluated, using hatchery-produced fingerlings (56-59 g initial weight) at stocking densities of five, 15 and 45 fish m^?3. During the first 9 months of a 12-month growout period, the fish were fed twice a day with a moist pellet feed containing 40.9% protein. From month 10 onwards until harvest, the fish were fed moist pellets in the morning and trash fish in the evening at a 1:1 ratio. The final weight of fish at harvest was up to 900 g, with mean weights of 544.6 ± 170.72 g at five fish m^?3, 540.2 ± 150.82 g at 15 fish m-^?3 and 513.3 ± 134.52 g at 45 fish m^?3. The results showed no significant differences (P > 0.05) in growth rate and fish size between the different stocking densities tested. The average daily growth rate ranged from 0.62 to 3.38 g fish^?1 day^?1, with mean weights of 1.49 ± 0.74 g fish^?1 day^?1 at five fish m^?3 through 0.53 to 2.38 g fish^?1 day^?1, 1.32 ± 0.57 g fish^?1 day^?1 at 15 fish m^?3 to 0.48-3.32 g fish^?1 day^?1 and 1.31 g fish^?1 day^?1 at 45 fish m^?3 stocking density. Although up to 100% survival was observed at the lowest stocking density, the survival rate significantly decreased (P < 0.05) with increasing stocking density. The food conversion ratio (FCR) significantly decreased (P <0.05) with increasing stocking densities, showing efficient feed utilization with increasing stocking densities of E. polyphekadion. The FCR averaged 2.1 at a stocking density of 45 fish m^?3. The yield in terms of kg fish produced m^?3 of water used in the culture system significantly increased (P < 0.001) from five to 45 fish m^?3. The yield averaged 17.3 ±0.53 kg m^?3 at a stocking density of 45 fish m^?3. The present results show that the present tank culture system could sustain more biomass in terms of increasing fish stocking densities. The growth performance of E. polyphekadion observed during this investigation has been reviewed with other grouper species.     

Stocking method effects on forage accumulation,canopy attributes,and nutritive value of grazed Mulato II brachiariagrass pastures

Rotational stocking (RS) is generally associated with the intensification of pasture-based animal production systems, although many studies have shown little advantage over continuous stocking (CS). The objective of this research was to describe and explain the effects of two average canopy heights (20 and 30 cm) and three stocking methods (CS; rotational stocking with lenient defoliation, RSL; and rotational stocking with moderate defoliation, RSM) on forage accumulation (FA), vertical distribution of plant-part components, and nutritive value of ‘Mulato II’ hybrid brachiariagrass (Brachiaria spp. syn. Urochloa spp.) during two summer rainy seasons in Piracicaba, São Paulo, Brazil. Pastures were maintained at average canopy height of 20 and 30 cm under CS, and treatments under RSL and RSM were imposed by variations of ±20 and 30% of the average canopy heights, representing defoliation intensities of 33 and 47% of the pre-graze heights, respectively. The FA was not affected by CS, RSL, RSM stocking methods, averaging 8090 kg DM ha⁻¹ year⁻¹. Canopy bulk density and distribution of plant-part components in the canopy profile were better at the average canopy height of 20 cm, accompanied by the greater nutritive value. The leaf bulk density was generally greater in RSM compared to CS. Pastures under CS had greater crude protein and in vitro digestible matter, and lesser neutral detergent fibre concentrations. Mulato II brachiariagrass should be managed at an average height of 20 cm under CS.     

Re-ensiling effects on inoculated sorghum: Intake,apparent digestibility,nitrogen balance,and animal feeding behaviour

This study aimed to determine whether using inoculants and re-ensiling in sorghum silages affect the intake and feeding behaviour, apparent digestibility, digestible energy, and nitrogen balance of sheep in maintenance. Half the sorghum was inoculated on the day of harvest, and the other half received the same inoculation volume but with water. Sorghum was ensiled in 100 experimental metal drum silos of 200 L covered with plastic: 50 silos with inoculants and 50 without them. After 56 days, 25 drums with inoculants and 25 without were exposed to air for 48 h. The other silos remained closed. The treatments were arranged in a 2 × 2 factorial scheme with inoculation and re-ensiling. The sheep received the silages after 211 days of ensiling and 155 days of re-ensiling to determine the intake, apparent digestibility, and feeding behaviour of animals. The experimental design was a simultaneous double 4 × 4 Latin square. The re-ensiling process increased silage pH, N-NH₃.TN⁻¹, butyric acid, and propionic acid. The inoculant increased propionic acid in ensiled and re-ensiled silages. Lactic acid concentration presented a statistical interaction with the inoculated and ensiled silage, 58% higher than the other treatment averages. The ADFap digestibility showed a complex interaction, in which the control ensiled and the inoculated and re-ensiled silages were about 35% lower than the inoculated ensiled silage. The Nbal:Nint ratio (g.g⁻¹) in the inoculated and re-ensiled silage had lower nitrogen retention than intake compared with the other treatments. These results indicate that exposing inoculated silages to air does not compromise their use in sheep feeding.     

Chemical and Physicochemical Properties of Maize Starch After Industrial Nixtamalization

Processing conditions similar to traditional nixtamalization are now used by the industry in the production of dry maize flours (DMF). The objective of this investigation was to evaluate the effect of industrial nixtamalization on maize starch. Thus, dent maize grains were sampled from storage silos and the starch isolated (S). From the same batch of maize, DMF was obtained and the starch isolated (S‐DMF). The amylose content in the starches was quite similar (21.5–23.4%) and characteristic of a dent maize. However, nixtamalization increased the calcium content in S‐DMF. The starches investigated exhibited the typical A‐type diffraction pattern after 40 days of storage at 11–84.1% rh. However, the differential scanning calorimetry (DSC) results showed that annealing of maize starch occurred during storage at 30°C. On the other hand, industrial nixtamalization has both a melting and annealing effect on maize starch. Thus, the operative glass transition temperature (T_g), and the DSC parameters that define starch gelatinization (T_p and ΔH) showed that the proportion between crystalline and amorphous regions within the starch granule and the extent of physical damage to starch were modified by nixtamalization. As an example, T_g for S was between 60 and 62.5°C, while the S‐DMF had a T_g of 45–55°C for damaged starch and 65–70°C for annealed starch. Additionally, the extraction of the nonconstitutive starch lipids provided starches with more consistent thermal properties, particularly in the behavior of gelatinization at different water content. This last observation might have important implications in the consistency of starch physicochemical properties and, consequently, in the quality of maize products such as tortillas.     

西班牙养猪密集地区同时流行A型流感病毒H1N2、H1N1和H3N2亚型的证据

本文报道了对西班牙养猪密集地区进行的猪流感病毒(SIV)血清学和病毒学调查结果,其目的是检测H1N2亚型猪流感病毒是否和在欧洲其它地区一样也流行于这些地区。在西班牙北部和东部地区100个未接种猪流感疫苗的繁育群采集了600份母猪血清,以进行抗H1N1、H3N2和H1N2亚型病毒的血凝抑制试验(HI);再借助鸡胚病毒分离法和商品薄膜免疫分析法,对采自有呼吸道疾患的225份病猪肺样本进行检测以确定是否存在猪流感病毒。通过HI和逆转录酶-聚合酶链式反应(RT-PCR)方法,再辅以cDNA部分序列的测定,对分离毒株进行鉴定。对血清所作的HI试验表明,在83%受测猪群和76·3%受测猪中至少存在抗一种猪流感病毒亚型的抗体。在受检的600份母猪血清中,仅含抗H1N2、H3N2或H1N1亚型病毒抗体的样本数分别为109份(占总样本比例的18·2%)、60份(10%)和41(6·8%)。从有呼吸道疾患的猪肺样本中分离到12株H3N2亚型病毒、9株H1N1亚型病毒和1株H1N2病毒。对H1N2亚型分离株的神经氨酸酶基因436个核苷酸序列进行的分析,进一步证实了其身份。显然,猪流感依然流行于所研究猪群中,同时一种新的亚型病毒(即H1N2亚型病毒)可能正在开始流行,并且也在西班牙引起了临床发病。     

Larvicidal and residual activity of imidazolium salts against Aedes aegypti (Diptera: Culicidae)

BACKGROUND

Aedes aegypti is an important mosquito species that can transmit several arboviruses such as dengue fever, yellow fever, chikungunya and zika. Because these mosquitoes are becoming resistant to most chemical insecticides used around the world, studies with new larvicides should be prioritized. Based on the known biological profile of imidazolium salts (IS), the objective of this study was to evaluate the potential of six IS as larvicides against Ae. aegypti, as tested against Ae. aegypti larvae. Larval mortality was measured after 24 and 48 h, and residual larvicidal activity was also evaluated.

RESULTS

Promising results were obtained with aqueous solutions of two IS: 1‐n‐octadecyl‐3‐methylimidazolium chloride ( C ₁₈ MImCl ) and 1‐n‐hexadecyl‐3‐methylimidazolium methanesulfonate ( C ₁₆ MImMeS ), showing up to 90% larval mortality after 48 h exposure. C ₁₈ MImCl was more effective than C ₁₆ mIMeS , causing mortality until day 15 after exposure. An application of C ₁₈ MImCl left to dry under ambient conditions for at least 2 months and then dissolved in water showed a more pronounced residual effect (36 days with 95% mortality and 80% mortality up to 78 days).

CONCLUSION

This is the first study to show the potential of IS in the control of Ae. aegypti. Further studies are needed to understand the mode of action of these compounds in the biological development of this mosquito species. © 2017 Society of Chemical Industry

     

Production and characterization of fibroin hydrogel using waste silk fibers

The use of natural resources, especially processing wastes, as low cost and environmentally friendly alternative aiming high value-added applications is a subject of broad interest. Since the Brazilian silk production annually generates a large amount of waste during the silk fibers processing, this work explores the preparation and characterization of silk fibroin hydrogels using spinning waste silk fibers from textile processing and the processed ones. Hydrogels were obtained directly by dialyzing silk fibroin solutions against frequent changes of water until the gelation point and then lyophilized and characterized in terms of their morphology, crystallinity, thermal resistance and secondary structure. X-ray diffraction analysis revealed the presence of β-sheet conformation related to sol-gel transition. FT-IR spectra indicated the coexistence of random coil (silk I) and β-sheet (silk II) structures, with predominance of β-sheet conformation for hydrogels from processed silk fibers. From thermogravimetric analysis the presence of β-sheet secondary conformation was demonstrated by a degradation peak around 292 °C for both hydrogels. Freeze-dried hydrogels presented sheet or leaf like morphology and no significant change was observed among the hydrogels from waste silk fibers and processed ones. These characteristics suggest that silk fibroin hydrogels prepared from spinning waste silk fibers and obtained directly by dialysis can be potential candidates for biomaterials application, such as drug delivery systems and for wound dressings.