Vol. 2 No. 3 (2019): Vietnam Journal of Agricultural Sciences

Neobenedenia girellae is one of the most pathogenic parasites affecting marine fish in captivity conditions. The use of chemicals for parasite prevention and treatment have several benefits; however, they can cause various negative side-effects. In an effort to discover cost-effective and sustainable practices, our current study was aimed at investigating the efficiency of freshwater treatments on N. girellae. A challenge test was conducted to produce infected fish which became materials for the freshwater immersion experiments. The duration and reaction of the parasites at different development stages from eggs to adult parasites were examined. Our findings revealed that 100% of the adults and oncomiracidia of N. girellae were killed quickly in freshwater. The eggs of N. girellae, however, were highly resistant to freshwater with a hatching success rate of more than 95% in all the freshwater immersion treatments (2, 5, 10 and 30min). The eggs hatched mainly on day 7 and finished hatching on day 8. Thus, the freshwater immersion method can be applied to treat N. girellae at most stages excepted for the egg stage. The best practical treatment for this parasite is to perform a replicated immersion recommended 8 days following the first treatment.

The purpose of this study was to apply the modified Kostiakov method to determine the soil infiltration rate and permeated water amount of Thuong River alluvial soil for orange plantations in Lang Giang district, Bac Giang province, Vietnam. The soil particle size ranged from 0.02 to 2.00mm mainly found in the surface horizon (>77.7%). The soil was slightly acidic in the surface horizon, and highly acidic in the subsurface horizons (pHKCl from 3.42 to 4.79). The organic matter content of the surface horizon was mederate, while it was very low in the other horizons. The total nitrogen (N) content was low (0.15%) in the surface horizon and very low in the subsurface horizons (0.02-0.06%) while the available N was medium. The total phosphorus (P) content in the surface horizon was high (0.4%) and medium in the other horizons. Available P in the surface horizon was high (18.6mg per 100g soil) and decreased in lower depths to only 0.3mg per 100g soil in the deepest (5th) horizon. The total and available potassium measurements were very low. A filtration characteristic model was developed by using the modified Kostiakov method for alluvial soil. The constant values a, a, and b of the equation y = ata + b were 0.8035, 0.758, and 0.00346, respectively, which were smaller than 1. The average percentage difference between the actual and calculated values by the model was only 0.141%, indicating that the calculated values can accurately predict the actual data measurements in the field. 

The objective of the study was to evaluate the effect of cow’s milk added to goat’s milk on physicochemical properties and sensory attributes of yoghurt. Yoghurts prepared from five different proportions of cow’s milk and goat’s milk were stored at 4-6ºC for 1, 7, and 14 days and then evaluated for their physicochemical (total solids, protein, pH, and acidity) and physical properties (viscosity and water holding capacity), and sensory characteristics (acceptability). The total solids of the evaluated yoghurts significantly increased, but the protein content decreased when the amount of cow’s milk increased in the mixtures of milk. The results showed that the pH value of the yoghurt made from only goat’s milk was higher, while the titratable acidity was lower than those of the yoghurts made from the mixtures of goat’s and cow’s milks. The yoghurt obtained from the mixture of milks containing 80% goat’s milk and 20% cow’s milk exhibited the highest viscosity and water holding capacity among the evaluated yoghurts. All the yoghurts received similar scores for color, odor, and texture after all periods of storage, while the highest score in terms of flavor was received for the yoghurt made from the mixture of milks containing 60% goat’s milk and 40% cow’s milk. Addition of cow’s milk to goat’s milk was shown to significantly contribute to the viscosity, water holding capacity, and flavor of the resulting yoghurts.

Although humans need ecosystems and ecosystem services for their survival and well-being, most of the global ecosystems and the services that they provide have declined and/or degraded rapidly over the past few decades. In order to find the ways to sustainably use natural resources, substantial efforts have been made to measure and value the ecosystem services. The term ‘ecosystem service’ was interpreted in different ways in the literature. For making correct decisions in natural resource management, a consistent way of defining and classifying ecosystem services is needed for valuation purposes. This paper argued for the need to divide ecosystem services into intermediate and final services.