Effect of fishmeal replacement with Artemia biomass as a protein source in practical diets for the giant freshwater prawn Macrobrachium rosenbergii

A 30-day feeding experiment was conducted in 160-L plastic tanks to evaluate the potential use of Artemia biomass as a protein source in practical diets for postlarval Macrobrachium rosenbergii (initial mean weight of 12.12–12.29 mg). Nine isoenergetic and isonitrogenous experimental diets (approximately 40% crude protein) were formulated by replacing levels of the fishmeal (FM) protein difference either with dried or frozen Artemia (0, 25, 50, 75 and 100%). The 0% Artemia treatment, in which Peruvian FM was the only main protein source, was considered to be the control diet. The results showed that prawn postlarvae (PLs) fed the FM control diet had a lower survival (46%) compared with all Artemia diets. Significant differences ( P <0.05) were, however, only found at 75% and 100% Artemia protein inclusion levels (survival of 68–77%). A gradual increase in growth performance (live weight gain, specific growth rate and total length) of the prawns was achieved on increasing dietary inclusion of Artemia protein. Additionally, the size distribution exhibited the same response as growth performance. However, prawns fed the frozen Artemia diets showed a better performance than the ones fed the dried Artemia diets. It can be suggested that Artemia biomass may totally replace FM in practical diets for PLs of the freshwater prawn M. rosenbergii .     

Comparison of serological tests for Trypanosoma evansi natural infections in water buffaloes from north Vietnam

In the present study, a collection of 415 water buffalo serum samples originating from the north of Vietnam was used for evaluation of different diagnostic antibody detection methods available to detect infections with Trypanosoma evansi. The diagnostic sensitivity and specificity of a direct card agglutination test (CATT/T. evansi), an indirect card agglutination test (LATEX/T. evansi) and a newly developed antibody detection ELISA (ELISA/T. evansi) was calculated on the basis of parasitological results, obtained by mouse inoculation, and compared for all assays. The immume trypanolysis assay with the predominant T. evansi RoTat 1.2 variable antigen type was used as reference test for antibody presence. All parasitologically confirmed animals (n=8) were positive in all tests. Diagnostic specificity was highest in CATT/T. evansi (98%) followed by the ELISA/T. evansi (95%) and the LATEX/T. evansi (82%). Concordance of the variant specific immune trypanolysis test with the other tests was calculated and revealed that few (1-8%) false positive results were actually due to a specific reactions, and that LATEX/T. evansi and ELISA/T. evansi detected more immune trypanolysis positives than the CATT/T. evansi. It was concluded that, apart from the immune trypanolysis test, which is not generally applicable, ELISA/T. evansi with a 30% positivity cut-off and LATEX/T. evansi, thanks to their superior capacity of detecting T. evansi specific antibodies, would be suitable as epidemiological tools detecting both active infections and persisting T. evansi specific antibodies. The ELISA/T. evansi with a 50% positivity cut-off and the CATT/T. evansi on the other hand, seem more appropriate to detect true infected water buffaloes.     

Comparative effects of fumonisins on sphingolipid metabolism and toxicity in ducks and turkeys

Fumonisins (FBs) are mycotoxins that are found worldwide in maize and maize products. Their main toxic effects have been well characterized in poultry, but differences between species have been demonstrated. Ducks appeared very sensitive to toxicity, whereas turkeys are more resistant. At the same time, alterations of sphingolipid metabolism, with an increase of the concentration of the free sphinganine (Sa) in serum and liver, have been demonstrated in the two species, but the link between the toxicity of FBs and Sa accumulation remains difficult to interpret. The aim of the present work was to compare the effects of FBs (10 mg FB1 + FB2/kg body weight) on sphingolipid metabolism in ducks and turkeys. Growth, feed consumption, and serum biochemistry were also investigated to evaluate toxicity. The main results showed that FBs increased Sa concentrations in liver and serum in ducks and turkeys, but these accumulations were not directly correlated with toxicity. Sa accumulation was higher in the livers of turkeys than in ducks, whereas Sa levels were higher in the sera of ducks than in turkeys. Hepatic toxicity was more pronounced in ducks than in turkeys and accompanied a decrease of body weight and an increase of serum biochemistry in ducks but not in turkeys. So, although FBs increase Sa concentration in the livers of both species, this effect is not directly proportional to toxicity. The mechanisms of FB toxicity and/or the mechanisms of protection of ducks and turkeys to the Sa accumulation within the liver remain to be established.     

Characterization of interactions between barley and various host-specific subgroups of Magnaporthe oryzae and M. grisea

The Magnaporthe oryzae–M. grisea species complex is composed of several host-specific subgroups, but does not contain a barley-specific subgroup. To characterize the relationship between barley and these subgroups, we inoculated 24 barley cultivars separately with each of 18 isolates from various hosts. The interactions between these cultivars and isolates included various reactions from nonhost-like immune responses to typical host responses. Evenly closely related isolates of the blast fungi caused such contrasting reactions. The immune responses of barley cultivars against a Setaria isolate, Si-1J, were examined in detail. An infection assay with near-isogenic fungal strains suggested that PWT1, which was first identified as a major gene conditioning the avirulence of Si-1J on wheat, was involved in the avirulence on two-thirds of the barley cultivars. At the cytological level, the immune responses were associated with both papilla formation and hypersensitive reaction (HR). Of these two, however, HR played a more critical role than papilla formation. Studying the interactions of barley with M. oryzae and M. grisea may reveal various steps in the process of host specialization of a parasite species and the concomitant evolution of host resistance.     

Effect of genotype,explant size,position, and culture medium on shoot generation of Gerbera jamesonii by receptacle transverse thin cell layer culture

An unique procedure for the mass shoot propagation of Gerbera using receptacle transverse thin cell layer (tTCL) culture procedure was developed. Genotype, flower bud age, explant size, position of receptacle tTCLs and culture media were found to affect the success of culture. Ten interspecific crosses of Gerbera showed different shoot regeneration rates and callus induction via receptacle tTCL culture, all of which had shoot regeneration rates higher than 57%. Flower buds collected on the 10th day resulted in 91% shoot regeneration after 6 weeks of culture on basal MS medium [Murashige, T., Skoog, F., 1962. A revised medium for rapid growth and bioassay with tobacco tissue cultures. Physiol. Plant. 15, 475–497] supplemented with 0.02 mg l⁻¹ thidiazuron (TDZ), 0.8 mg l⁻¹ adenine and 10% (v/v) coconut water (CW). This was significantly higher than those from flower buds on the 7th and 14th days (22% and 54%), respectively. Shoot regeneration rate was the highest (94–100%) in the middle layers of the receptacle. For mass shoot propagation, shoot clusters were subcultured on half-strength MS medium supplemented with 0.5 mg l⁻¹ indole-3-butyric acid (IBA), 0.5 mg l⁻¹ 6-benzyladenine (BA) and 2.0 mg l⁻¹ kinetin after every 4 weeks. Plantlets formed when single shoots were cultured on half-strength MS medium containing 1 mg l⁻¹ IBA. All plantlets acclimatized well in the greenhouse.     

The effects of dietary lipid sources and lecithin on the production of giant freshwater prawn <Emphasis Type="Italic">Macrobrachium rosenbergii</Emphasis> larvae in the Mekong Delta region of Vietnam

The giant freshwater prawn, Macrobrachium rosenbergii, is cultured widely in the Mekong Delta region of Vietnam but it is often difficult or expensive for hatchery operators to purchase commercial diets used as a feeding supplement to Artemia nauplii. Therefore, in the present study, the effects of lipid sources and lecithin on the growth and survival rate of M. rosenbergii larvae were examined in order to develop suitable hand-prepared larval diets for seed production of M. rosenbergii in this area. Six egg custard diets consisting of various ratios of lipid (originating from soybean oil and squid oil) and lecithin were used for rearing Macrobrachium rosenbergii larvae. Treatments in which larvae were fed diets containing squid oil exhibited the highest body length and survival rates (7.14–7.43 mm and 51.1–68.1%, respectively), and differed significantly from other treatments (P<0.05). Use of dietary soybean oil yielded the lowest body length and survival rates (6.29–6.75 mm and 22.0–48.7%), respectively). The supplementation of dietary lecithin did not increase final body weight but did improve larval survival rates. The n-3 HUFA content of prawns fed dietary squid oil was higher than those of animals provided with other diets. These results indicated that the most appropriate diet for rearing M. rosenbergii larvae is the diet containing 3% squid oil and 1.5% lecithin.     

Salinization intensifies the effects of elevated temperatures on Channa striata,a common tropical freshwater aquaculture fish in the Mekong Delta,Vietnam

Fisheries Science - Increasing water temperatures and salinity intrusion due to climate change are serious challenges for freshwater aquaculture. In this study, we assessed the combined effects of...     

Ecophysiology of Acacia species in wet–dry tropical plantations

Selected tropical Acacia species are used extensively for short-rotation plantation forestry in many parts of Asia and, to a limited degree, in Australia. We explored leaf-level photosynthetic activity and leaf water potential (Ψleaf) of three field-grown Acacia tree species (aged between 7 and 18 months) in contrasting wet–dry tropical plantations in southern Vietnam and northern Australia. Light-saturated photosynthetic rate (A1500) declined throughout the morning and early afternoon in the dry season; in the wet season, levels remained high and relatively constant throughout most of the day. Maximum daily A1500 at 09:00 ranged from 22.2 μmol?m?2?s?1 in the wet to 10.4 μmol?m?2?s?1 in the dry season. At both locations, trees were able to extract soil water such that pre-dawn leaf water potential (Ψpd) remained>?1.5?MPa even at the end of the dry season. Stomatal conductance to water vapour (gs) did not respond to decreasing Ψleaf during the wet season but was sensitive to changes in Ψleaf in the dry season. Species comparisons of the relationships between A1500 and Ψleaf revealed different strategies to balance carbon uptake and water loss in a wet–dry environment. Acacia crassicarpa and A. mangium regulated Ψleaf to a greater extent than the A. mangium×A. auriculiformis hybrid such that ?Ψleaf (determined as Ψpd?midday Ψleaf) was unaffected by season. This result suggests that the hydraulic regulation of tree water status varies amongst young tropical Acacia species. From a management perspective, for Acacia species that tend to strongly regulate water loss in environments with an extended dry season, overall productivity at the end of a rotation may be less than for species that prioritise carbon gain.     

Development of large and small blastomeres from 2‐cell embryos produced in vitro in pigs

In the present study, we examined the development to blastocysts of large and small blastomeres from unevenly cleaved 2‐cell embryos (uneven 2‐cell embryos) in pigs. Proportion of blastocysts derived from large blastomeres (52.8 ± 6.4%) was significantly higher (P < 0.05) compared with small ones (32.1 ± 4.6%). However, there were no differences in total cell number, inner cell mass (ICM) cell number and ICM/total cells ratio between them. Of 53 sister blastomere pairs in the same embryos examined there were 12 pairs (22.6%) in which both blastomeres developed to blastocysts, 16 pairs (30.2%) in which only large blastomeres developed to blastocysts, and five pairs (9.4%) in which only small blastomeres developed to blastocysts. Relative total amount of active mitochondria in small blastomeres were lower (P < 0.05) than that of large blastomeres and blastomeres from evenly cleaved 2‐cell embryos. However, there was no difference in relative density of active mitochondria in these three types of blastomeres. In conclusion, blastocysts derived from small and large blastomeres in uneven 2‐cell embryos had comparable quality in terms of cell number, ICM number, ICM/total cell ratio and distribution of active mitochondria. The results suggest that these blastomeres may contribute multiple offspring production in pigs.