Vol. 16 No. 5 (2018)

This study was conducted to examine the effect of salinity fluctuation frequency on molting rate and growth of postlarval white-leg shrimp (Litopenaeus vannamei). Individal shrimp was stocked in 5 L plastic bottle containing 2 L of 20 ‰ seawater with 04 treatments including salinity fluctuation in an amplitude ± 0‰ (NT1; ĐC), and an amplitude ± 5‰ with a frequency was set in 2 days (NT2), 4 days (NT3) and 6 days (TN4), 30 replicates each. The initial weight and length of postlarva was 0.007 g/ind. and 0.97 cm/ind., respectively. The results showed that the shorter molting frequency (4.9 days/times) and higher molting rate (22.1 %/day) were obtained in the treatment (NT4) where salinity fluctuation frequency was set in 6 days. In contrast, longer molting frequency (5.3 days/times) and lower molting rate (20.5 %/day) was obtained in the constant salinity treatment (ĐC). In addition, the highest growth in terms of weight after 45 days culture were obtained in NT4 (0.88 g/ind.), followed by NT3 (0.85 g/ind.), NT1 (0.83 g/ind.), and NT2 (0.74 g/ind.). The results of this study indicated that the higher molting rate and shorter molting frequency lead to significantly better growth of shrimps when salinity fluctuation in 6 days frequency was applied, compared to constant salinity.

The study was conducted to evaluate the effect of Pennisetum purpureum, Biden pilosa, Brachiaria ruziziensis and Leucaeana leucocephala in the diet on feed intake, milk yield and quality of Saanen goats. All animals were assigned in a 4×4 Latin square design to receive four dietary treatments with 4 roughages in 4 stages. The results showed that dry matter, crude protein, lipid and ash intake were significantly different among treatments (P<0.05). Milk yield/week and milk yield/day in the dietary treatment with Leucaeana leucocephala were highest (16.13 and 2.31l, respectively) and lowest with Pennisetum purpureum (7.28 and 1.04l, respectively). Feed comvertion ratio (FVR) for milk production was lowest in the diet with Leucaeana leucocephala (2.62 kg) and highest in the diet with Pennisetum purpureum (7.42 kg). Dry matter, fatness, nonfat solids, protein, density and freezing point were not significantly different among dietary treaments (P>0.05). In conclusion, the use of the diet with Leucaeana leucocephala increases the nutrients intake, improves milk yield, reduces feed convertion ratio for milk production and does not affect milk quality of Saanen goats.

An experiment was conducted to evaluate the efficiency of liquid fermented green forages in pig production. A total of 30 F1 (Y x MC) fattening pigs with body weight of 25.30-26.20 kg were randomly divided into three groups which were uniform in breed, sex, body weight and age. The control group (DC) was fed complete feed; Two expermental groups (TN1 and TN2) were fed 60% complete feed + 40% of fermented green forage in which TN1 group was fed 25% high fiber-roughage + 75% high protein roughage and TN2 was fed 50% of high fiber roughage + 50 % high protein roughage. The results showed that the feed conversion ratio was not significantly different among treatments (3.59 in DC group compared with 3.66 and 3.65 kg of feed (88% DM) per kilogram of weight gain in TN1, TN2, respectively), but, the feed cost was reduced by 29-30%. Feeding of fermented green forage diets did not significantly affect pork meat quality in all treatments. Fermented green forage increased the economic efficiency of pig production.

The study was performed to evulate the efficacy of “made-in Vietnam” progesterone releasing device in regulating the reproductive cycle of dairy herd in Bavi district, Hanoi, from February 2017 to November 2017. That applying of Ovsynch plus intravaginal device (ProB in the experimental group; CIDR® in the control group) resulted in high rate of estrus expression in both groups; especially during the period of 2-3 days post-treatment. In addition, the estrus rate according to BCS and parity of the cows was also assessed, which revealed that the cows with lower parity were more active with the protocol than those with higher parity (above 3th parity). It is also noted that the distribution of oestrus cows mainly concentrated on the BCS ranging from 2.75 to 3.0. With the feasible results of determinating the vaginal irritation as an effect of the devices, the authors tentatively recommended introducing ProB to dairy cows across the country.

The study was carried out on Co Lung ducks from one day of age to 11 weeks of age in Thanh Hoa province in order to evaluate the carcass yield and meat quality. The results showed that at 9, 10 and 11 weeks of age the dressing percentage was 67.97,68.31 and 69.73%;the leg percentage was 12.24,12.98,and 12.95%, and the breast percentage was 12.06,12.94,and 12.96%, respectively.When the slaughter ageincreased, the loss of leg and breast weight during storage period and after cooking decreased while the toughnessincreased. The value of pH15 ranged from 5.82 to 6.35, pH24 ranged from 5.60 to 6.10. The meat color (L*) ranged from 42.80 to 46.74 while leg muscle was darker than breast muscle. Dry matter content of meat ranged from 23.01 to 24.46%, total mineral content from 1.23 to 1.32%, crude lipid content from 1.86 to 2.18%, and crude protein content from 18.61 to 20.41%. Co Lung duck meat contained a well-balanced array of amino acids,especially, essential amino acidswhich were higherat 10 weeks of age in comparison with 9 weeks of age.

The aims of this study were (1) to assess thewater quality and sediments and (2) to propose solutions for aquatic resources management of the West lake. Water and sediments samples for analysis were taken at 10 sitesduring the dry and wet season of 2017. The results showedthat the water quality didnot meet the quality requirementsfor aquatic conservation purposes in accordance with the QCVN08-MT: 2015/BTNMT (A1). The values of BOD5, COD and PO43-and TSS were higher than the allowable limits. High levels of chlorophyll a and total nitrogen showedthat the water qualityin the lakewasin the form of eutrophication and hypertrophication. The levels of heavy metals (Pb, Hg, Cd, Cu, As, Zn)andoil in the water andheavy metals (Pb, Cd) in the sediment were lower than the Vietnamese standards. The sediments of West Lakehada neutral environment withweak alkaliandweak oxidation.

This study aimedto assess genetic diversity and genetic difference between two Ri chicken lines and other chicken breeds using 15 microsatellitemarkers. The resultsshowed that genetic diversity of Ri hoa mo chicken and Ri vang rom chicken lines was 0,682 and 0,647, respectively. The inbreeding coefficientofRi hoa mo chicken and Ri vang rom chicken lines was 0.01 và 0.042, respectively. There was no genetic difference between Ri Hoa mo chicken and Ri vang rom chicken lines. However, the highestgenetic distance was found between Ri vang rom chicken and Luong Phuong chicken. The genetic dissimilaritiy among chicken populations was related to their geographical distribution. Ri hoa mo chicken and Ri vang rom chicken were in the same group while chicken populations from the northern part and the southern part showed genetic differentiation andseparatedfrom the Chinese breed.

The objectives of the study were to evaluate i) effect of ecological zones of fresh and brackish water on rice-shrimp cultivation systems, (ii) chemical characteristics of soil and water of the agro-ecological zones, and (iii) the efficiency of liming on rice growth and yield. Field experiments were conducted during August to December 2013 in Phuoc Long and Hong Dan, Bac Lieu province. Results showed that, after shrimp harvest, Phuoc Long planted rice crop in August when soil salt concentration was high (ECe: 8.0 mS/cm; ESP: 13.8%). Exchange cations in the soil decreased in the descending order: Mg2+>Na+>Ca2+>K+, corresponding to 8.0>3.0>1.5>1.0 meq/100 g, respectively. Due to salt accumulation in the soil in brackish water zone, ECe and ESP were at high levels during December (5,6 mS/cm and 7,8%, respectively), unfavourable for growth and yield of rice in comparison with fresh water zone at Hong Dan. Lime application to the salt-affected soil in Phuoc Long reduced salt damage to rice in terms of panicle number per square meter, filled grain rate, and higher grain yield (by 0.6 t ha-1) as compared to without liming. However, lime application  to rice soil in fresh water zone at Hong Dan did not significantly increase the grain yield.

Soil salinization results fromaccumalation of soluble salts in soil, which negatively influences agricultural production activity, makingproductive land areas nonsuitable for farming or reducing crop yield. Theobjective of this study wasto analyze the status of salinization of agricultural land in Hau Giang province using inverse distance weighting (IDW) method. The results revealedthat the percentage of the non-salinized agricultural land (<0.25%)accounted for higher percentage of44.23% of the total agricultural land. The percentage of ​​agricultural land area with the soluble salt level at0.25-0.5% occupied30.79% of the total agricultural land, mainly located in Long My district and Long My Town. With the soluble salt level of 0.5-0.75%, 24.98% of the total agricultural land areawasaffected, mainlyin the distrits of Phung Hiep, Chau Thanh, Chau Thanh A and Long My. The salinization in Hau Giangwasmainly caused by seawater intrusionas well as salinized groundwater.Suitable irrigation methods, salt-tolerant crop varieties and lime (CaCO3) could be applied to reduce the adverse effect of salinity of agricultural land areas affected withmoderate level of total soluble salts(0.5-0.75%).

This study aimed to determine the effect of ripeness on the accumulation of some bioactive compounds in Thuy Hong tomato cultivar to identify suitable time for harvest and consumption. Tomatoes were harvested at 5 ripening stages (RS) for analysis of bioactive compounds, in which phenolic contents and antioxidant activities were measured by Folin-ciocalteu and DPPH methods, respectively. During ripening, vitamin C content increased dramatically from 2.25 to 27.17 mg/100 g fresh weight (FW) from RS1 (green) to RS5 (red, soft). The accumulation of phenolic compounds increased significantly from RS1 to RS3 (light orange-yellow color), then almost unchanged to RS5. Carotenoid content rised intensely during ripening; At RS1 carotenoid content was 598.81 μg/100 g FW, and then increased of 12.6 times at RS5. Antioxidant activity increased dramatically from RS1 to RS3, then remained unchanged to RS5. This increase would be due to the accumulation of in phenolics and carotenoids during maturation. RS5 seems to be the suitable for consumption due to its high content of bioactive compounds.

Rice straw after harvest need to cut and dry before collection and storage. Large volume of rice straw to be handled in a short time requires mechanical operation. At present, the collection system was established, but the number, types and features remain limited and mainly used to collect straw after harvest. The article introduces the basis for the establishment and construction of a rational working mode of the windrow straw harvester. The machine system was designed on the basis of combining two-wheeled tractor power and rice harvesting device widely used today. With this solution, a windrow straw harvester can be quickly constructed with a reasonable working mode, meeting the practical requirements and raising the efficiency of agricultural production.

This article investigated the technical efficiency and factors affecting the efficiency in sugarcane production in Thach Thanh district, Thanh Hoa province. To estimate technical efficiency, we used the stochastic production function (SPF) with data collected from 105 sugarcane producers. Our study indicated that the technical efficiencies of sugarcane production were 82.53%. Factors affecting the technical efficiencies included education of household heads, the participation of extension system and the adoption of sugarcane varieties. The adoption of technology procedures guided by extension officers can improve sugarcane yields.

Nghiên cứu này tập trung phân tích các tố ảnh hưởng đến chất lượng lao động trong ngành tiểu thủ công nghiệp tỉnh Bắc Ninh. Nghiên cứu dựa trên kết quả phỏng vấn 261 người lao động về 48 tiêu chí khác nhau trong lý thuyết về chất lượng lao động. Phân tích nhân tố khám phá và mô hình hồi quy được sử dụng nhằm nhóm các tiêu chí trên và phân tích ảnh hưởng của các yếu tố trích xuất đến chất lượng lao động. Các yếu tố trích xuất bao gồm: Chính sách phúc lợi người lao động, điều kiện làm việc, cơ hội nghề nghiệp, trình độ giáo dục và đào tạo, chính sách lương thưởng, điều kiện máy móc thiết bị, hệ thống chăm sóc sức khỏe người lao động. Kết quả mô hình hồi quy cho thấy các yếu tố trích xuất trên có mối quan hệ tương quan thuận với chất lượng lao động ngành tiểu thủ công nghiệp. Nhằm nâng cao chất lượng lao động ngành tiểu thủ công nghiệp tỉnh Bắc Ninh, các cơ quan chính quyền địa phương và các doanh nghiệp tiểu thủ công nghiệp cần cải thiện điều kiện làm việc cho người lao động, cung cấp các khóa học và đào tạo chuyên môn thích hợp và đồng thời chú ý nhiều hơn đến công tác chăm sóc phúc lợi người lao động và cơ hội nghề nghiệp. Chính sách lương thưởng, điều kiện máy móc trang thiết bị và hệ thống ý tế hiện tại được duy trì ở mức độ hài lòng đối với đa số người lao động.