Abstract
Background:
The usage of commercial probiotic products as alternatives to traditional antibiotics in fish culture is initiated to be a potential factor for Nile tilapia fish’s welfare and growth.
Aim:
The purpose of the current study is to show the influence of commercial probiotics (Bacillus amyloliquefaciens) dietary supplementation at different levels on Nile tilapia welfare and growth.
Methods:
Apparently healthy fingerlings of Nile Tilapia with a total number of 120 with an average initial weight (26.2±0.3 g) were distributed into 4 groups (each group had 30 fingerlings). The 1st group (G1) was given a basal diet without additional probiotics. While other groups (2nd group (G2), the 3rd group (G3), and the 4th group (G4)) were given basal diets supplemented with different levels of commercial probiotics (1 g, 2 g, and 3 g of probiotics per kilogram of diet) respectively (15 fish in each sub group as replicate), in eight glass aquaria (30×40×100 cm) for 2 months as an experimental period.
Results:
The results revealed that the probiotic treated groups especially G4 (3 g probiotics /kg diet) showed a marked increase in the following behavioural patterns such as feeding and swimming behaviours, while G2 (1 g probiotic /kg diet) had an increase in the foraging behaviour compared with G1 control group. While surfacing, body care, and aggressive behaviours with its all patterns were the highest in control group (G1) than the all probiotics treated groups. Crossing test showed that fish rose at the probiotic treated groups (G3, and G4) were more active and could achieve the highest growth rates. While, water quality was better in G4 (3 g probiotic /kg diet) than other groups. Moreover, G4 (3g probiotic /kg diet) showed a marked increase in all serum biochemical parameters than the control group (G1).
Conclusion:
The current study proved that the best level of commercial probiotics (Bacillus amyloliquefaciens) was (3 g probiotic/kg diet) for achieving optimal Nile tilapia fingerlings’ growth performance under these experimental conditions. Finally, this work confirms the significance of addition of probiotics as a feed additive to enhance both growth performance and immunity response, improve water quality and achieve welfare of Nile tilapia fingerlings.

Key words: Probiotics, Behavioural patterns, Crossing test, Growth rate, Welfare