Vol. 18 No. 3 (2020)

To determine the kind of organic nutrient solution which is conformed to the circulating hydroponic technology by using the growth media bed for water spinach. Experiment 1 was conducted to evaluate the effect of different concentrations of V.M 1954 organic nutrient solutions (0.5‰, 1.5‰ and 2.5‰) on the growth, productivity and quality of water spinach in summer season 2017 at Center for Organic Agriculture Promotion and Studies, Vietnam National University of Agriculture. The results showed that the concentration of 1.5‰ was optimal for the growth, development and productivity of water spinach. To further evaluate some more types of organic nutrient solutions as a hydroponic solution, experiment 2 was carried out to determine the effects of 03 types of organic nutrient solutions (V.M 1954, Vegano and TNC Hume) to the growth, yield and quality of water spinach by using a circulating hydroponic system and growth media bed in summer and summer-autumn seasons, 2019. The attained results indicated that the V.M 1954 organic nutrient solution was the best for the growth, yield and quality of water spinach. From the results of experiment 1 and 2, we have confirmed that water spinach could fully grow and well develop for good productivity and quality, and simultaneously reduce pests and diseases when grown in circulating hydroponic technology using growth media bed with organic nutrient solution V.M 1954 (1.5‰ concentration).

This study aimed to investigate the epidemiological, pathological characteristics and diagnostic methods affected fish. The survey from 207 fish raising farmers with 294 ponds in 5 Northern provinces, accompany with sampling the affected fish were conducted for analysis the clinical, pathological features and PCR assay. The results showed that polyculture was predominant culture type (89.6%), and grafted average ratio of 31% common carp in ponds. Affected fish appeared in the months surrounding the Lunar New Year, with clinical signs of respiratory distress, lethargic swimming, separate from the shoal, excess mucus and necrotic in the gills, loss of epidermis and fin erosion, reddening of the skin. Gross lesion includes the kidney or liver may be enlarged and adhesions in the abdominal cavity of internal organs. The proportion of ponds existed KHV infected fish was accounted for 37.1%, with 70 fish samples from contaminated ponds were positive with KHV in PCR assay.

This study was conducted to exam the reproductive performance of crossbred beef cattle F1(BBB ×Sind crossbred) and growth performance of the offspring raised in Ba Vi, Hanoi. 20 F1(BBB ×Sind crossbred) and 20 F2 [BBB ×F1(BBB ×Sind crossbred) including 10 males and 10 females from birth to 6 months of age were used. The results indicated that the reproductive performance of crossbred beef cattle F1(BBB ×Sind crossbred) was relatively good. The age at the first puberty, at first breeding and first calving was 425.6, 451.85 and 759,8days, respectively. The calving interval and interval from calving to the first service was 372.2 and 82.3 days, respectively. The calving rate was 98.03%. The conception ratio was 1.35. The offspring from F1(BBB ×Sind crossbred) and BBB breed had good growth performance. Bodyweight at birth, 4 and 6 months of age was 30.55, 144.05 and 202.55kg, respectively. The average daily gain at the period of birth to 4 months, 2-4 months and 4-6 months were 941.67, 950 and 975 g/head/day. Therefore, it is possible to use crossbred beef cattle (BBB ×Sind crossbred) as a basis for further increasing BBB blood to produce a next crossbred with better performance and meat quality.

The study was conducted on Co Lung ducks in Ba Thuoc district, Thanh Hoa province and Co Lung ducks on the third generation at Dai Xuyen Duck Research Center to survey the numbers, distributions of Co Lung ducks in Ba Thuoc district and evaluate morphological characteristics of Co Lung ducks. The results showed that the number and distribution of Co Lung ducks in Ba Thuoc district are mainly congregated at 6 communes of Quoc Thanh area, including Ban Cong, Co Lung, Lung Niem, Lung Cao, Thanh Lam and Thanh Son commune. Co Lung ducks have been raised by both grazing and semi-grazing methods. Feed sources used were self-mixed feed and local agricultural production. It was observed that at one day of age, the plumage color is mostly dark gray and pale yellow. In mature, the plumage color is mostly dark brown. The main morphological characteristics of Co Lung duck is: short leg, big head, short neck and medium body. The length of the body of Co Lung duck is 24.72cm in male and 24.82cm in the female; the breast size of the male is 30.06cm, the female is 29.80cm with breast size/ body length ratio of 1.22 and 1.20; The feet height of a male is 7.58cm and female is 7.35cm; The length of wing feathers of male and female duck are 16.36 and 16.23cm respectively.

The aim of this study was to identified the virulence factors and the pathogenesis of Vibrio parahaemolyticusin farmed white leg shrimp in Thua Thien Hue province. In this study, 8 isolates of V. parahaemolyticuswas recovered from diseased white leg shrimp that showed typical clinical signs of AHPND such as pale-to-white hepatopancreas (HP), significant atrophy of the HP, softshells, guts with discontinuous, or no contents, black spots or streaks visible within the HP. The bacteria were identified as V. parahaemolyticusby using API 20E kit (BioMerieux). Four of 8 isolates have been detected that caused AHPND by using IQ Plus™ AHPND/EMS Plasmid Kit. Data of this study showed that the production of caseinase, phospholipase, haemolysin and mobility of these isolates were significantly stronger than others. The LD50 of isolate that caused AHPND was 105 cfu/mL. By contrast, experimental shrimp were healthy without any clinical signs and no mortality was observed in the treatment immersed in the isolate lacking toxin genes. This study showed strong relationship between virulence factors and pathogenesis of V. parahaemoliticus caused AHPND in shrimp.

This study aimed to determine the types and densities of live foods that affect the growth and survival of grouper larvae (Epinephelus malabaricus) from 0 to 12 days old. In the first experiment, the feeding regime consisted of four types of live feeds (three rotifer strains: Proales similis, Brachionus rotundiformis, Brachionus plicatilisand the trochophore of Pacific oyster) for larval nursing. The results showed that super small rotifers (Proales similis) (size 50-60µm) were most suitable for larval rearing of grouper to 12 days old. In experiment 2, the densities of rotifer (P. similis) at 10 individuals/ml and 15 individuals/ml were showed the best results in nursing of larval grouper, denoted as the survival rate of 12-day-old larvae was 8.3-11.7%; the population’s subdivision coefficients and the average length of grouper larvae were 4.4-8.8% and 601.8-603.6μm, respectively.

This study was conducted to evaluate the effectiveness of tea seed oil (TSO) compared with the addition of some antioxidant substancessuch as BHA, BHT, d-α-tocopherol during storagetime(at 60C for 12 days according to the Schaal experiment, 2010) for susceptible oils such as linseed oil (LSO) and walnut oil (WNO). Peroxide (PV) and Para-anisidine (P-av) values ​​were monitored during oxidation of the two oils at 0and 12 days of storage. The Totox value has assessed the formation of LSO first and second oxidation products after 12 days of storage in the control and formula supplemented with 0.02% BHA + BHT, 0.03% tocopherol, 3% TSO, 6% TSO respectively 176.06; 139.3; 154.38; 138.34 and 110.31. In WNO, this value was 204.56 respectively; 173.12; 177.93; 170.46 and 154.29. In this study, TSO was shown to have higher potential than BHA, BHT, tocopherol when blended with 6% TSO. Blending 3% TSO had preservation effect as good as BHA + BHT at the concentrations of 0.0 2% and D-α-tocopherol at 0.03% in inhibiting the oxidation of LSO and WNO.

The linkage of production and marketing, especially in the field of agriculture is always an encouraging direction for the development of many economies in the world. However, little information on theoretical issues ofthe linkage is available. Therefore, this study focuses to making comments and assessments to select concepts, terms and content about the linkage between farmer households and enterprises in agricultural production and marketing. Through the collection, analysis, evaluation of secondary information, some related concepts and terms are mentioned under different perspectives such as farmer household, businesses and the linkage between farmer households and enterprises in agricultural production and marketing. Besides, the contents of linkage emphasize the field and form of the linkage, organizational structure, binding rules, implementation management and the currently attained results and the effectiveness have been brought by the linkage. Simultaneously, we have discussed on the hypotheses of two main groups of factors which affect this linkage, including the external and internal factors (characteristics of farmers- household and enterprises participating in the linkage, characteristics of agricultural products, the complexity of the process of joining the linkage, benefits from linkage, lack of linkage opportunities and price risk). Based on some theoretical conclusions about linkage, this study will provide useful information for future relevant studies.