Natural remedies against vibriosis in shrimp culture - Liptosa

A phytobiotic was able to reduce Vibrio counts in intestine and hepatopancreas leading to an increase in survival and better health.

Shrimp farming is growing very fast in recent years, due to the high profit margins which present a good opportunity for those with interest in this sector. In Asia the production of Pacific white shrimp (Litopenaeus vannamei) was more than 3 million tonnes in 2015 with a value of USD 14 billion (FAO Statistics, 2015).

Despite the efforts to produce specific pathogen free or SPF post larvae from hatcheries, farmers have to face continuous disease outbreaks along the production cycle. Pathogen free production does not exist as the pond ecosystem environment comes with high levels of bacteria and parasites. Some bacteria are needed for the culture while some are opportunistic. The balance between these pathogens is crucial in shrimp production, especially to avoid growth reduction and high mortalities. Even so, farmers are always exposed to the presence of acute hepatopancreatic necrosis disease/early mortality syndrome (AHPND/EMS), white spot syndrome virus (WSSV), Enterocytozoon hepatopenaei (EHP) and white faeces disease (WFS) disease.

Phytotherapy

Phytotherapy provides efficient solutions to the cultured animal helping them to fight against parasites, bacteria and/ or fungal pathogens. Preventive strategies together with best management are vital for better profitability and sustainable farm production. The continuous inclusion of phytobiotics in the feed produces healthier animals, with better immune system and growth performance. An experiment was carried out with the phytobiotic from Liptoaqua-Liptosa, Spain, made with organic acids, plants and essential oils in Kasetsart University for 60 days showed positive results in survival and growth in Pacific white shrimp. The study started with post larvae (PL10) transported from the hatchery and acclimated for 2 days in fiberglass tanks at the Aquaculture Business Research Centre (ABRC) laboratory. Nine fibreglass tanks (500 L) were used in this experiment and shrimp were stocked at a density of 80 shrimp/tank (120 PL/m2). Salinity during the acclimation period and experiment was maintained at 25 ppt.

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Figure 1. The average survival rate of Pacific white shrimp at 15, 30, 45 and 60 days of feeding with different diets.

The phytobiotic Liptofry shrimp was top dressed on a feed from Charoen Pokphand Thailand (CP) with 36% crude protein, 5% lipids and 4% ash then mixed with fish oil and allowed to dry for 15 minutes. Three experimental groups were prepared with three tanks per group:

• Control group (without Liptofry shrimp);
• Phytobiotic inclusion at 5 kg/tonne; and
• Phytobiotic inclusion at 8 kg/tonne

Growth and survival

Shrimp were fed four times daily to satiation according to standard feeding rate. Water quality parameters such as pH, dissolved oxygen (DO), ammonia and nitrite were measured weekly throughout the experiment period. At the end of the 60 day feeding trial, shrimp from all the groups were weighed. Growth and survival rates of shrimp were statistically compared. Five shrimp from each tank were sampled for total Vibrio spp counts in the hepatopancreas and intestine.

Our results showed that shrimp fed with the phytobiotic at the dose of 5 kg/tonne had the highest survival rate of 84.7±1.15%, which was significantly higher than the group fed with phytobiotic at 8 kg/tonne (78.7±1.15%) and the control group (76.7±1.15%) (P< 0.05, Figure 1).

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The average body weight (ABW) of shrimp is shown in Figure 2 while the food conversion ratio (FCR) of shrimp fed different diets is shown in Table 1. After the 60-day feeding trial, shrimp from the two groups fed with Liptofry shrimp had significantly higher (P<0.05) body weight and FCR compared with the control group.

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Figure 2. The ABW of Pacific white shrimp at 30, 45 and 60 days of feeding with different diets.

Table 1. The feed conversion ratio (FCR) of Pacific white shrimp after 60 days of feeding with different diets.

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Bacteria counts

The average total number of bacteria and Vibrio spp. in the intestine of shrimp throughout the study period is shown in Table 2. Shrimp fed with the phytobiotic at the dose of 5 and 8 kg/ tonne had significantly (P< 0.05) lower number of total bacteria and Vibrio spp compared with the control group over the 30 days until 60 days feeding period.

The average total number of bacteria and Vibrio spp. in the hepatopancreas of shrimp is shown in Table 3. Shrimp fed with the phytobiotic at the dose of 5 and 8 kg/tonne had significantly (P< 0.05) lower number of total bacteria and Vibrio spp compared with the control group over the 30 days until 60 days feeding period.

Table 2. Bacteria and Vibrio spp. in the intestine of Pacific white shrimp.

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Table 3. Bacteria and Vibrio spp. in the hepatopancreas of Pacific white shrimp.

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Conclusions

Liptofry shrimp at 5 kg/tonne showed significantly higher survival rate compared with the other treatment groups (10%). Irrespective of dose, the phytobiotic showed significantly higher average body weight and lower feed conversion ratio compared with the control group. At 5 kg/tonne, the phytobiotic improved feed conversion ratio by 27% when compared to the control. The total number of bacteria and Vibrio spp. in shrimp fed with the phytobiotic was in all cases, significantly lower than the control group both in the intestine and in the hepatopancreas.

The continuous inclusion of Liptofry shrimp at 5 kg/tonne in the whole cycle can improve significantly the production parameters with reduced Vibriosis outbreaks.

This article was originally published in AQUA Culture Asia Pacific Magazine, July/August 2017