Abstract
Determining the optimum application dosage of probiotic in biofloc system is often challenging because the microbial community seems to exert similar effects irrespective of their dosages. It is however noted that certain dosages promote higher yield in shrimp culture more effectively. Principal component analysis was adopted to identify these optimum dosages where 1-way ANOVA could not clearly identify due to the effects of microbial community. The effect of varying application dosages of probiotics in a shrimp culture system on growth indices and water quality variables were studied in a culture trial of Litopenaeus vannamei that lasted for 84 days in an indoor biofloc culture system. Only 4 (26.66 %) of variables showed significant difference in the 1-way ANOVA conducted. Principal Component Analysis (PCA) was used to illustrate the dimensional interactions among variables. Contributions of observation points at 7 ml.l(-1) (Obs1-3), 14 ml.l(-1) (Obs 4-6), and 21 ml.l(-1) (Obs 7-9) were analyzed. The Obs 4-6 (representing 14 ml.l(-1)) had the highest mean contributory effect (11.03) indicating the greatest impact recorded in the PCA relationships among growth indices and water quality variables. It was concluded that probiotic dosages can be determined in biofloc system based on the contributory effect it enhances in the measured variables.•Microbial community in biofloc affects the clear distinctions of the dosages due to proliferations•1-way ANOVA alone may not show dosage-related variations.•PCA could identify the optimum probiotic dosage that would enhance shrimp growth performance and maintain favourable water quality conditions in biofloc aquaculture systems.