The effect of Lactiplantibacillus plantarum BE7 and Lacticaseibacillus paracasei BUM6 as feed supplement on growth performance and pathogen resistance in Oreochromis spp

Probiotic inclusion as a dietary supplement has demonstrated numerous benefits for the aquaculture industry, particularly in improving productivity and profitability. As the use of antibiotics can promote the emergence of resistant strains and fish vaccines are often costly to implement, probiotics present a more practical and sustainable alternative for disease mitigation in cultured fish. However, the effectiveness of probiotic supplementation is strain-specific and varies according to tolerance to gastrointestinal stress conditions and aquaculture environments, limiting the efficacy of many commercially available products. This study aimed to evaluate the probiotic potential of two locally isolated probiotic strains from Malaysian fermented foods, Lactiplantibacillus plantarum BE7 (belacan) and Lacticaseibacillus paracasei BUM6 (budu) and their effects on the growth performance, survival, and disease resistance of red hybrid tilapia (Oreochromis spp.) against fish pathogens, Streptococcus agalactiae and Aeromonas hydrophila. In vitro screening was conducted to assess tolerance to gastrointestinal, environmental stress conditions and antagonistic activity against S. agalactiae and A. hydrophila. This was followed by a 14-week feeding trial to evaluate growth performance, feed utilization, survival, and disease resistance to pathogens. Both probiotic strains demonstrated high tolerance (>60%) to bile, pH, and salinity stress and exhibited strong inhibitory activity against the tested pathogens. After 14 weeks of feeding trial, fish fed with L. plantarum BE7 showed significantly higher survival rate, specific growth rate (SGR), absolute growth rate (AGR), and improved feed conversion ratio (FCR) compared to other groups (P < 0.05). Following pathogen challenge, L. plantarum BE7-fed fish exhibited significantly improved survival and reduced disease severity. These findings suggest that L. plantarum BE7 has potential as functional probiotic for dietary application to enhance growth performance and disease resistance of tilapia culture in Malaysia.