Here are some key points from the presentation made by Dr. Olivier Decamp, PhD, Farm & Feedmill Product Manager, INVE Belgium at Aqua India 2018, Chennai on the 3rd February 2018.
White Faeces Syndrome – Signs
- Faeces become pale white, float on water surface
- Hepatopancreas becomes whitish and soft, shrunken.
- Transformation, sloughing and aggregation of Hepatopancreatic microvilli into vermiform bodies resembling gregarines
- Associated loose exoskeleton and epibiotic protozoa leading to dark discolouration of the gills.
- Reduced feed intake (increased FCR)
- Weak animals, and mortality
- Worst after 50-90 DOC
Reports of White Faeces Syndrome
- 1996. Malaysia, “Soft body-white faeces syndrome” (Yang et al., 1999)
- 2009. Thailand (Tourtip et al., 2009; Limsuwan, 2010)
- 2010. China (Huang, Jie and So (2010, 2011)
- 2010. Vietnam (Ha et al, 2010)
- 2010. Malaysia (Thong, 2016)
- 2014. Indonesia (Thong, 2016)
- 2015. India (Durai et al, 2015; Mastam, 2015)
White Faeces – Possible Causes
- Poor feed quality (mycotoxins, Anti nutritional factors present in plant based protein sources etc.)
- Gregarines – No evidence yet to link gregarines with white faeces
- Cyanobacteria (toxins or low digestibility)
- Vibrio
- Enterocytozoon hepatopenaei (EHP) associated with WFS but alone does not cause white faeces. EHP by affecting the growth rate of shrimp may increase the risk of overfeeding, and resulting poor rearing conditions. By affecting the shrimp metabolism, EHP may affect the ability of shrimp to fight other pathogens
White Faeces Syndrome – Factors
Poor water quality
- Poor preparation of pond
- Incorrect biosecurity measures prior stocking, aiming at both viruses and bacteria
- Unstable phytoplankton
- Algal bloom and crash, stressing shrimp
- Incorrect N:P balance supporting the growth of cyanobacteria
- Poor management
- Insufficient aeration to maintain DO > 4 or 5mg/L (1HP for 300-400Kg)
- No control of ammonia and nitrite
- No control of sulphide
Poor bottom quality
- Overfeeding
- Higher water temperature g increased appetite, leading to risk of overfeeding
- Lower shrimp growth rate than expected — feeding not adapted
- Too high application of molasses, etc.
- Unstable phytoplankton
- Algal bloom and crash, creating anaerobic sediment
- Poor management
- Accumulation of waste in pond bottom
- Insufficient aeration to support degradation of waste
How to act against WFS
- Start with clean and healthy animals (Broodstock, larvae, PL)
- Work with clean environment. Follow disinfection routines
- Control EHP in previously affected pond
Pond sediment treatment (Flegel 2016, RGCA Newsletter 2016)
- Apply CaO (quick lime,burnt lime, unslaked lime or hot lime) at 6MT/ha
- Plough the CaO into the dry pond sediment (10-12 cm).
- Moisten sediment to activate lime
- Leave for one week before drying or filling
- After application of CaO, the soil pH should rise to 12 or more for a couple of days and then to the normal range as it absorbs carbon dioxide and forms CaCO3
- Vibrio control with Probiotic treatment – Probiotic that remains active in farm conditions
- Waste control in ponds – Removal of white faeces, moults
- Control organic waste, using microbial products alone or in combination with oxidizing agents
- Control vibrio load in shrimp gut
- Reduce vibrio and improve utilization of nutrients – Better growth and FCR
Conclusions
- Prevent pathogen(s) transfer from one phase to the other
- Focus on EHP and Vibrio
- Prevent pathogens from (re)colonizing shrimp through waste removal/control
- Consider nutrition, health and environment
Source: Aquaculture Spectrum