Effects of dietary potassium diformate (KDF) on growth performance, feed conversion and intestinal bacterial community of hybrid tilapia (Oreochromis niloticus ♀ × O. aureus ♂)

The aim of the present study was to investigate the effect of dietary inclusion of potassium diformate (KDF), a possible non-antibiotic growth promoter, and two widely-used antibiotics, flavomycin and quinocetone, on growth performance, feed conversion ratio and gut microbiota of hybrid tilapia. An 8 week feeding trial was conducted with five levels of KDF: 0 (C), 3.0 (KDF3), 6.0 (KDF6), 9.0 (KDF9), and 12.0 (KDF12) g kg− 1 diet and three antibiotic treatments: flavomycin (8 mg kg−  1, AF), quinocetone (100 mg kg−  1, AQ), and flavomycin (4 mg kg−  1) + quinocetone (50 mg kg−  1) (AFQ). At the end of the experiment, fish were starved for one day and bulk weighed. Pooled gut contents sampled from four replicate tanks were analyzed for bacterial community by 16 S rDNA PCR, denaturing gradient gel electrophoresis (DGGE) and Bio-1D++ software. The results indicate that the addition of dietary KDF and antibiotics had no significant effect on tilapia growth performance, feed conversion ratio or survival compared to the control group. Among the experimental groups, however, fish fed the KDF3 and KDF6 diets showed improved growth performance and feed conversion ratio with higher final body weight and specific growth rate and lower feed conversion ratio compared to those fed the AFQ diet. Dietary KDF and antibiotics showed effects on the gut microbiota. Dietary KDF3 and KDF6 improved the relative richness of some intestinal allochthonous bacteria such as Mycobacterium sp. partial MHSD12-like, Mycobacterium peregrinum-like, Pseudomonas sp. HMPB4-like and six uncultured bacterium-like species. However, alpha Proteobacterium IMCC1702-like, Rhodococcus sp. P14-like, and three uncultured bacterium-like species were depressed in the gut. Based on these results, the possible beneficial effects of KDF on gut bacteria will be discussed.