Growth of Incumbent Firms and Entrepreneurship in Vietnam

This paper analyzes the relationship between the performance of incumbent firms and the net entry of new firms by combining various theoretical views of entrepreneurship. Different regression models to treat dynamics and endogeneity issues are applied to test the research hypothesis with regional micro‐data for 61 Vietnamese provinces from 2000 to 2008. The main finding is that net entry is associated with the performance of incumbent firms and the overall performance of the economy. Incumbents' growth and gross domestic product growth induce changes in the existing production system and stimulate the creation of an economic environment more favourable to new firm formation. Consistent with the hypotheses put forward within the “knowledge spillover,” the “error‐correction,” and other approaches, incumbents may generate new entrepreneurial opportunities not only for themselves but also for the whole society.     

Preparation of oligoalginate plant growth promoter by γ irradiation of alginate solution containing hydrogen peroxide

Degraded alginate compounds with molecular weights of 7-26, 40-77, or 11-26 kDa were obtained by γ irradiation, hydrogen peroxide (5% H(2)O(2)) treatment, or a combination treatment involving ionizing radiation and H(2)O(2), respectively. The 14 kDa oligoalginate, prepared by the combined method, promoted the growth of mustard greens and lettuce at an optimal concentration of 75 mg/L. The growth promotion effects of the oligoalginate prepared by γ irradiation in the presence of H(2)O(2) were statistically equivalent to those of the oligoalginate prepared by γ irradiation only. The combination of γ irradiation and H(2)O(2) reduced the required irradiation dosage by a factor of 9 relative to the oligoalginate produced by γ irradiation only. The combination treatment (γ irradiation/H(2)O(2)) may be carried out on a large scale at low cost to produce oligoalginate for use as a plant growth promoter in agricultural industries.     

Susceptibility of Arcanobacterium pyogenes from different sources to tetracycline, macrolide and lincosamide antimicrobial agents

Chlortetracycline, oxytetracycline, and the macrolide, tylosin, are extensively used for growth promotion and disease prophylaxis in the cattle and swine industries in the US. Arcanobacterium pyogenes, a common inhabitant of the mucosal surfaces of cattle and swine, is also a pathogen associated with a variety of infections in these animals. A broth microdilution technique was used to determine the antimicrobial susceptibility of 48 A. pyogenes isolates to macrolides, lincosamides and tetracyclines. The MIC50 and MIC90 for chlortetracycline were 0.12 and 8 mg/l, respectively. Similarly, the MIC50 and MIC90 for oxytetracycline were 0.25 and 8 mg/l, while the MIC50 and MIC90 for tetracycline were 0.25 and 16 mg/l, respectively. The MIC50 and the MIC90 were < or = 0.06 and >64 mg/l, respectively, for erythromycin, tylosin and clindamycin. This resistance pattern indicated that some of these A. pyogenes isolates may carry an MLS(B) resistance determinant. A. pyogenes isolates (12.5%) were resistant to erythromycin, and this percentage doubled when MICs were performed following induction with erythromycin. Of the 48 A. pyogenes isolates, 25 and 41.7% were resistant to MLS(B) antimicrobial agents and the tetracycline derivatives, respectively. MLS(B) resistance was present in 22.2 and 35.3% of A. pyogenes isolates of bovine (n=27) or porcine (n=17) origin. In contrast, 70.6% of porcine isolates were resistant to the tetracyclines, compared with 25.9% of bovine isolates. These data suggest that a large proportion of A. pyogenes field isolates may be resistant to these commonly used antimicrobial agents.     

Prevention of porcine Clostridium difficile-associated disease by competitive exclusion with nontoxigenic organisms

Clostridium difficile is widely known as a cause of disease in humans, and has emerged as an important problem in neonatal swine. No commercial product is available for immunoprophylaxis of C. difficile-associated disease, but success in preventing experimental infections in hamsters by use of nontoxigenic strains to competitively exclude toxigenic strains led us to try this method in neonatal pigs. Spores were administered orally to newborn pigs or were sprayed onto perineum and teats of dams. Significantly more piglets were weaned among litters receiving spores orally, and average weaning weights were significantly higher for both treatment groups than for controls. Toxins A and B were detected in 44.8% of litters and 16.5% of piglets born to sprayed sows and 58.3% of litters and 15.4% of piglets in the control group. However, toxins were detected in only 13.8% of litters and 3.4% of piglets given spores orally. These data support a contention that precolonization by a nontoxigenic strain can ameliorate the pre-weaning growth retardation associated with C. difficile infection in piglets.     

Determining the distributions of soil carbon and nitrogen in particle size fractions using near-infrared reflectance spectrum of bulk soil samples

This study aimed at assessing the potential of near-infrared reflectance spectroscopy (NIRS) for determining the distribution of soil organic matter (SOM) in particle size fractions, which has rarely been attempted. This was done on sandy soils from Burkina Faso (three sites) and Congo-Brazzaville (one site). Over the total sample set, NIRS accurately predicted carbon (C) and nitrogen (N) concentrations (g kg^?1 fraction) in the fraction <20 μm. When considering Burkina Faso only, predictions were improved in general; those of C and N amounts (g kg^?1 soil) became accurate for the fraction <20 μm but not for the coarser fractions, probably due to heterogeneous SOM repartition. However, most SOM being <20 μm in general, NIRS could be considered promising for determining SOM size distribution.     

Evaluation of some intestinal cytokines genes expression and serum innate immune parameters in common carp (Cyprinus carpio) fed dietary loquat (Eriobotrya japonica) leaf extract

The aim of this study was to illustrate the effects of dietary loquat leaf extract (LLE) on the expression of some intestinal cytokines as well as serum innate immune parameters in common carp (Cyprinus carpio) fingerlings. The fish were fed with experimental diets supplemented with 0 (control), 0.25% (0.25LLE), 0.5% (0.5LLE) and 1% (1LLE) LLE over a 7‐week period. At the end of the trial, the serum lysozyme (Lys) activity, ACH50, total Ig as well as the expression of IL1B, IL8, TNF‐alpha, LYZ and TGF‐β in intestine were evaluated. The results showed that administration of 0.5% or 1% LLE significantly increased serum total Ig. However, in case of serum Lys activity significant elevation was observed just in fish fed 0.5% LLE. Also, supplementation of diet with LLE significantly increased ACH50 compared to the control group, regardless of inclusion levels. Gene expression studies revealed upregulation of TNF‐alpha, IL1B, IL8 and LYZ in intestine of fish fed LLE. However, the effects varied dependent on LLE levels and the tested immune related gene. Also, in case of TGF‐β significant downregulation was observed just in 1% LLE treatment. In conclusion, dietary LLE supplementation significantly upregulated immune related genes in intestine and improves innate immune responses. Altogether, LLE can be recommended as fish immunostimulant in early stage of carp culture.     

Effect of dietary eucalyptol on stress markers,enzyme activities and immune indicators in serum and haematological characteristics of common carp (Cyprinus carpio) exposed to toxic concentration of ambient copper

In the present study, protective effects of dietary eucalyptol were investigated against copper toxicity in common carp (Cyprinus carpio). The fish were fed with diets supplemented with 0 (control), 0.5% and 1% eucalyptol for 14 days before exposure to 0.25 mg/L ambient copper for 7 days. Blood samples were taken from the fish before and 1, 3 and 7 days after copper challenge. Before copper challenge, eucalyptol significantly decrease serum aspartate aminotransferase (AST) activity, but increase blood WBC, RBC, hematocrit and haemoglobin, serum lysozyme, total immunoglobulin (Ig) compared with the control. Copper exposure led to stress, tissue damage and immunosuppression. After the copper challenge, significant elevation in serum cortisol, glucose, alanine aminotransferase (ALT) and AST, but decrease in blood RBC and WBC, and serum lysozyme, complement (ACH50) and total immunoglobulin (Ig) was observed. Eucalyptol administration significantly mitigated the increase in serum cortisol, glucose, ALT and AST, and decrease in WBC, ACH50, lysozyme and total Ig. Dietary 1% eucalyptol had significantly higher protective effects than 0.5% in the case of serum AST, lysozyme, total Ig and ACH50. In conclusion, eucalyptol has beneficial health effects on common carp and enables to mitigate copper‐induced stress, tissue damage, and immunosuppression. Eucalyptol at the dietary 1% level is recommended to protect common carp against adverse effects of copper toxicity.     

Effects of natural dietary carotenoids on skin coloration of false Clownfish (Amphiprion ocellaris Cuvier, 1830)

This study was performed to evaluate the effect of dietary natural carotenoid sources on skin colour enhancement of false clownfish Amphiprion ocellaris. The juvenile fish (initial body wt. 0.30 g) were fed with four experimental diets including (a) commercial feed (reference diet), (b) moist feed, (c) sweet potato (potato diet) and (d) dried gut weed Enteromorpha sp. (gut weed diet). Sweet potato and gut weed were used to boost up β‐carotene levels in the diets. There was no significant difference in final weight (0.51 ± 0.02 – 0.61 ± 0.01 g) and length (2.80 ± 0.02 cm) of fishes among treatments (p > 0.05) after 8 weeks. The survival rate of the fish in all dietary treatment was greater than 89%. Principal component analysis results showed that fish fed potato and gut weed diets performed brighter colour in skin with more orangeness, body and accumulated β‐carotene levels were higher than those fish fed with reference diet. Indicator a* value for the redness of fish fed potato diet (16.18 ± 0.59) and gut weed (14.36 ± 2.14) was also higher than fish fed reference diet (10.92 ± 0.82). The result of this study provided key information for developing dietary colour enhancement of ornamental fish by using cost‐effective feed ingredients (potato and gut weed) as natural supplemental carotenoid sources.     

Effects of dietary turmeric administration on stress,immune, antioxidant and inflammatory responses of common carp (Cyprinus carpio) during copper exposure

The present study assessed the effects of dietary turmeric on Cyprinus carpio resistance and responses to copper exposure. First, the fish were assigned to four treatments received diets supplemented with 0 (control), 5, 10 and 20 g/kg turmeric for 3 weeks. Thereafter, the fish were exposed to lethal concentration (3.5 mg/L) of ambient copper for 24 hr and mortality was 65.3%, 41.8%, 22.7% and 20.6%, respectively. In the second experiment, the fish were fed with the aforementioned diets and simultaneously exposed to sub‐lethal concentration (0.25 mg/L) of ambient copper for 3 weeks. Copper exposure led to increases in plasma cortisol, glucose, malondialdehyde (MDA), alanine transaminase (ALT) and aspartate transaminase (AST), and decrease in plasma T₄, T₃, lysozyme, alternative complement haemolytic (ACH50), bactericidal activities, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and blood red blood cell count (RBC) and haemoglobin. Moreover, copper exposure led to significant upregulation of tumour necrosis factor‐alpha (TNF‐a) and interleukin 1‐beta (IL1‐b), and significant downregulation of interleukin 10 (IL10) gene expressions in the fish liver. Turmeric administration at 10 g/kg significantly mitigated/inhibited the copper‐induced negative effects, which seems to be due to the augmenting of the antioxidant defence.