การประยุกต์ใช้ Tetraselmis sp. เพื่อการเลี้ยงกุ้งในระบบน้ำเขียว และการใช้โปรไบโอติกในอาหารกุ้งสำหรับต่อต้านเชื้อ Vibrio parahaemolyticus

Abstract

Application of microalgae, Tetraselmis sp., in green water system cooperating with utilization of probiotics mixed feed in shrimp culture was performed for the purpose that this may be resistance to Vibrio parahaemolyticus, causing the shrimp disease. It may be one of the ways to protect the shrimp production lost from this pathogen in the shrimp culture industry. The experiments were divided into 3 parts, which the first was to study the growth of Tetraselmis sp. and photosynthesis bacteria (PSB) at the different concentration levels of organic milk. The second was to study the effect of yogurt and PSB mixed feed for the shrimp culture to grow and survival rate of Pacific white shrimp (Litopenaeus vannamei) in the culture system with and without Tetraselmis sp. in the system. The last experiment was to study efficacy of yogurt และ PSB utilization by mixing in the shrimp feed for testing the resistance to V. parahaemolyticus in the shrimp culture in the system with and without Tetraselmis sp. The first study on the growth of Tetraselmis sp. and PSB by culturing in the outdoor in a 10-liter jar for 1 week using organic waste milk from a dairy factory (Dairy Home Co., Ltd.). In Tetraselmis sp. culture, 4 different concentrations of the organic waste milk were set as 0.25, 0.50, 1.00 and 2.00 percent. While in PSB culture, 4 different concentrations of the organic waste milk were set as 10, 20, 30 and 40 percent. The growth was studied by measurement of absorbance (optical density, OD) with Spectrophotometer at 680 nm wavelength (OD680) for Tetraselmis sp. and 970 nm wavelength (OD970) for PSB. The result on Tetraselmis sp. growth was that on the 3rd day, Tetraselmis sp. cultured in 2% organic milk showed the highest optical density (OD680) at 0.094 nm. The second highest ones were cultured in 1.00, 0.50 and 0.25 % organic milk, which the values at OD680 were 0.092, 0.078 และ 0.046 nm, respectively. Moreover, there was no statistically difference on the ones which were cultured in 1 and 2 % organic milk (p>0.05). In PSB culture, the result was that PSB cultured with 40% organic milk showed the highest OD (OD970), which was 0.328 nm following with PSB cultures with 30, 20 and 10% (0.315, 0.268 and 0.265 nm), respectively. When the result was statistically analyzed at 95% confidence, the growth of PSB cultured with 40% organic milk showed the statistically significant difference with those cultured with 10, 20 and 30% organic milk (p<0.05). However, there is no statistically significant difference with those cultured with 10 and 20% organic milk. The second experiment on introduction of Tetraselmis sp. for applying in the Pacific white shrimp culture system cooperating with conducting of probiotics, yogurt and PSB, mixed in feed for the shrimp culture for 5 weeks. The result was that no statistically significant difference in the weight gain, specific growth rate, growth rate per day and feed conversion ratio (FCR) was found in all treatments and the control (p>0.05). However, the survival rates of the shrimp cultured with probiotics mixed feed was higher than those in the control. The treatment cultured with PSB mixed feed showed the highest survival rate at 95.00 % which was statistically significant difference compared with the control (p<0.05). In the shrimp culture treatments without Tetraselmis sp. in the system for 5 weeks, no statistically significant difference in the weight gain, specific growth rate, growth rate per day, FCR and survival rate of the shrimp (p>0.05). The third part of the research was to study the efficacy of the probiotics, yogurt and PSB against V. parahaemolyticus. In the shrimp cultured in a system with Tetraselmis sp. and those without Tetraselmis sp., the resistance against V. parahaemolyticus was tested by immersing the shrimp in V. parahaemolyticus at a concentration of 1×107 CFU/ml for 2 hours and then were cultured for 1 week. The result was that the shrimp cultured in a system with Tetraselmis sp. in the set fed with probiotics showed the significantly difference in the highest survival rates (p<0.05) compared with the control. In the shrimp cultured in the system without Tetraselmis sp., the lowest survival rate at 36 hours was only 13 %, which was a statistically significant difference (p<0.05) compared to those fed with the probiotic supplemented feed. At the end of the experiment, the color of shrimp after boiling was measured using a CIE L* a* b* colorimeter (L* brightness value, a* red value and b* yellow value). The result was that the shrimp raised in the systems containing Tetraselmis sp. with probiotic supplemented feed showed significantly different a* and b* values compared to the control (p<0.05). In the shrimp cultured in the system without Tetraselmis sp., there was not significant difference in the a* values of the shrimp fed both types of probiotics (p>0.05). However, there was a statistically significant difference (p<0.05) in the shrimp fed with yogurt and PSB supplemented feed compared to the control. From the results, it can be concluded that Tetraselmis sp. is effective against V. parahaemolyticus when the white leg shrimp were cultured in the system containing this algae. In addition, the probiotics, both yogurt and photosynthetic bacteria, were effective against V. parahaemolyticus when the shrimp were fed with the probiotic supplemented feed. Therefore, both Tetraselmis sp.and the probiotics, yogurt and photosynthetic bacteria, were applied together in the white leg shrimp culture can enhance shrimp immunity to V. parahaemolyticus, add the survival chance, increase the shrimp productivity and improve the color of the shrimp.