The aquaculture industry in Ghana is predominantly hinged on Nile tilapia farming. Nile tilapia production constitutes more than 70% of total annual aquaculture production in the country. Attempt at increasing Nile tilapia production has been met with the challenge of disease outbreaks, most of which are of bacterial origin. One of the dominant bacterial pathogens is Streptococcus agalactiae, which has two serotypes (1a and 1b) documented as present and causing high mortalities in most farms. Farmers have resorted to the use of antibiotics to treat these diseases. However, globally, this practice is frown upon due to environmental and consumer health concerns. An eco-friendly alternative is the use of probiotics which are live microorganisms that when fed to fish confer growth and health benefits to them, with no known negative implications on the consumer’s health.
The objective of this study was to evaluate the effects of three dietary probiotic products (PB1, PB2 and PB3) on growth performance and control of Streptococcus agalactiae infection in juvenile Nile tilapia. The probiotic diets were prepared using a basal diet containing 40% protein for juvenile tilapia. They were added to the basal diet based on the manufacturers’ dosage as follows: PB1: 12.5 ml/kg; PB2: 0.1g/kg and PB3: 5g/kg whiles the control group was fed the basal diet. Fifteen fish of mean weight 10 g were placed in 40L aquaria tanks (3 replicates/diet) in a flow through system and fed the diets for 12 weeks before the challenge with S. agalactiae. Water quality parameters were recorded over the 12 weeks and fish weights determined fortnightly. Serum bactericidal activity was analysed pre and post challenge. Fish were challenged through IP injection with S. agalactiae at 1.5 x108CFU/ml. Results showed no significant difference in growth parameters of the control and probiotic diets (P=0.047). However, there was significant difference in percent mortalities of fish fed the control and probiotics diets after the pathogen challenged (P=0.000000000299).