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• Effects of Calcium Levels in Artificial Pellet Feed on the Growth and Survival Rate of Black Apple Snails (Pila polita)

  Le Van Binh, Ngo Thi Thu Thao

  Received: Feb 13, 2019 / Published: Aug 30, 2019

   Abstract PDF

  The present study was conducted to evaluate the effects of different dietary calcium levels on the growth and survival rate of black apple snails (Pila polita) in the grow-out period. There were 3 replicates for each treatment and the snails were fed with five calcium levels (% dry matter) in diet as follows: 1% (Ca1), 3% (Ca3), 5% (Ca5), 7% (Ca7), and 9% (Ca9). Two-month-old juveniles with an average initial body weight of 2.13g, shell height of 21.71mm, and shell width of 16.35mm were reared in tarpaulin tanks (1 × 1 × 1m; 40cm water depth) at the density of 100 individuals per tank. After 4 months of the rearing period, the average body weight, shell height, and shell width of the snails reached the highest values in the Ca5 treatment (28.43 g, 54.97 mm, and 40.09mm, respectively) and these values were significantly different compared to the remaining calcium contents (Ca1, Ca3, Ca7, and Ca9). The survival rate of the snails in Ca3 (75.7%) was higher than in Ca1 and Ca7 (74.7%), Ca5 (73.7%), and Ca9 (71.7%). However, the survival rate was not significantly different among the treatments. Snails in Ca5 obtained the highest productivity (2.88 kg m-2) and this value was significantly different from Ca1 (2.55 kg m-2) and Ca9 (2.35 kg m-2). The results of this study showed that the growth rate and productivity of black apple snails were highest when they consumed a diet containing 5% calcium. The optimum requirement of calcium for the black apple snails in the grow-out period was 4.51%.

• The Impact of Capital Investments on Firm Financial Performance – Empirical Evidence from the Listed Food and Agriculture Companies in Vietnam

  Dang Thi Hai Yen, Nguyen Thi Huong, Dao Thi Hoang Anh

  Received: May 11, 2022 / Published: Mar 29, 2023

   Abstract PDF

  Capital investment is one of the most important financial decisions of a firm, which effects the business survival. This paper investigates the impact of capital investments on firm performance to provide an insight for future capital investment decisions of companies. The study uses unbalance panel data gathered from 62 companies which covered 688 observations of listed food and agriculture sector in Vietnam stock exchange during the period 2009 – 2020. To control for unobserved individual effects, the random effect estimator was employed. Profit margin (PM) is used as a proxy for firm performance, while independent variables are capital investment rate in both short-term and long-term effect, equity to total assets ratio, firm size and tangible to fixed assets ratio. The results indicate that capital investments have statistically significant positive impact on long-term performance of the analyzed enterprises. This outcome is in accordant with many previous studies. Especially in the context of Vietnam listed food and agriculture companies have high level of capital investment, a portion increase in capital investment rate will increase the company profit margin. Other variables also have statistically significant relationship with profit margin, in details, equity ratio and size have positive effect while tangible assets ratio has negative effect on firm performance. Therefore, the research suggest firm managers should choose the appropriate capital investment strategies in long-term perspective, within the consideration of equity ratio, economics of scale and tangible assets investment ratio to get the most efficient performance.

• A Practical and Efficient Method for the Micropropagation of Japanese Cherry (Prunus sp.)

  Nguyen Thi Thuy Linh, Pham Thi Ngoc, Ninh Thi Thao, Nguyen Thi Phuong Thao

  Received: Feb 15, 2019 / Published: Feb 16, 2019

   Abstract PDF

  This study was conducted to establish the procedure for in vitro propagation of Japanese cherry (Prunus sp.) to produce large quantity of plantlets and initial planting materials for climate adaptation research of this plant in Hanoi. Single nodal stems were used as the primary explants and initially produced shoots on MS medium supplemented with 1 mg L-1 BA. The highest shoot multiplication rate (9.57 times) was obtained on MS medium containing 1 mg L-1 BA and 0.25 mg L-1 a-NAA after 8 weeks of culture. 100% of the shoots produced roots with a mean of 10.10 roots per plant within 4 weeks on ½ MSM medium with 4 mg L-1 IBA. The survival rate of in vitro derived plantlets after a 6 to 7-week-period of rooting during acclimatization using a soil: coco peat: smoked rice husks (2:2:1, v/v/v) substrate was 100% and acclimatized plantlets showed good growth and development. This is the first report on a practical and efficient in vitro multiplication protocol for Japanese cherry in Vietnam, starting from shoot initiation to establishment of plants under greenhouse conditions.