TRIAL TO ASSESS THE EFFECTIVENESS OF CAPLUS ME ON GROWTH, SURVIVAL & FOOD CONVERSION OF RED NILE TILAPIA, Oreochromis Niloticus, DURING SEX REVERSAL

Alex Diana* and Tilman Wilke
 
Dr. Eckel Animal Nutrition GmbH & Co. KG
E-Mail: a.diana@dr-eckel.de

In order to obtain best outputs, most of the tilapia farmers choose to use only male tilapia in the grow-out stages. It is known that male tilapia is more profitable in terms of volume since they grow bigger and faster and they are energy efficient. Female tilapia tend to waste energy and time due to breeding. A common technique to produce only male tilapia is hormone sex reversal using methyltestosterone. The period of sex reversal is a critical phase in the production cycle and farmers are especially concerned about survival of fry.

The objectives of this studies was to test whether an organic acid product (CaPlus ME from Dr. Eckel animal Nutrition, Germany) added to the diet of red tilapia during sex reversal in hapas in PE-lined ponds is beneficial in terms of growth and survival of fry.

Ten 5m2 hapas were set up in a two PE-lined ponds and stocked with 20,000 red tilapia swim-up fry.  They were fed for 21 days on fish meal containing 60 ppm 17α-methyltestosterone (MT) for a period of 21 days. The feed allocated per day was divided into five feeds and fed at 08:00, 9:30, 11:30, 13:30 and 16:30 by broadcasting the powdered feed over the water surface. The test diet was prepared by mixing the product into the fish meal before addition of the ethanol/MT solution and then mixed thoroughly in a blender-type mixer.

Aeration was provided in each pond via the use of 12 home-made diffusers made of PVC pipe and material. Hapas were changed with 10 m2 hapas after 15 days to allow the young fish to have more space to grow.

Survival in the control was lower than usual, even for red tilapia, but the treatment showed much higher survival.  The Caplus ME was also good with survival of 74% compared to the control of 52%.

Since survival was higher in the test treatments, individual fish size was less due to the effect of density.  

Total harvest of fish per hapa was higher in the CaPlus ME treatment at 22283 individuals compared to 15599 in the control.  Further studies will continue to see if the results can be repeated.