The increased demand for food production drives the intensification of Nile tilapia (Oreochromis niloticus) production, making breeding programs essential to achieve this goal. When managing these programs, new genetic material should be introduced after multiple generations to reduce inbreeding and enhance genetic diversity. Evaluating production performance when including new genetics and focusing on the role of feed additives, are crucial to understanding their impact on breeding programs. Therefore, this study aimed to evaluate the growth performance and hepatosomatic index of two genetic strains of Nile tilapia from the genetic improvement program fed with β-Glucan + Mannan oligosaccharide (βG+MOS). The experimental design was a 2 × 2 factorial with two genetic groups and two treatments: diets with and without βG+MOS.
The groups consisted of the 12th generation of the Tilamax genetic improvement program (TILAMAX) and a cross between Tilamax and an introduced test strain (CBTILAMAX). A total of 96 tilapias (31.1 ± 5.7 g) were weighed, measured and distributed into 16 aquariums (6 fish/aquarium; 24 fish/group; n=4). The initial total length and initial standard length were 11.40 ± 0.83 cm and 9.42 ± 0.69 cm respectively. The 41-day experimental period maintained optimal water conditions by daily monitoring. At the end of the feeding trial, the K factor (CFFTL and CFFSL, hepatosomatic index (HSI), final weight (FW), total length (FTL), and standard length (FSL) were measured, and other production performance parameters were computed based on the final data. The condition factor showed that all the groups exhibited adequate health and growth during the experiment, with no differences in strain or use of additives. The hepatosomatic index also did not differ between groups. Similarly, no significant differences were observed for standard lengths, total weight gain (TWG), condition factors, and specific growth rate (SGR). Based on these results, it is concluded that there were no differences between TILAMAX and CBTILAMAX related to performance under the effect of feeding with βG+MOS. These results support the successful integration of the test strain into the Tilamax genetic improvement program and provide a foundation for future studies with this strain.