DIET AFFECTS THE GUT MICROBIOTA AND NUTRIENT ASSIMILATION PATTERNS OF GENETICALLY IMPROVED FARMED TILAPIA Oreochromis niloticus

Nile tilapia, Oreochromis niloticus are the third most commonly farmed finfish species in the world, accounting for nearly 5% of the overall production of global aquaculture. In the past few decades much of the success of this species has been attributed to the development and distribution of Genetically Improved Farmed Tilapia (GIFT). Despite the ever-increasing availability of GIFT, the productivity of small-scale farming remains highly variable, particularly in developing nations. Commercial fish feed pellets can increase fish farm productivity, however, for small scale farmers these pellets are often inaccessible due to the high cost and farm remoteness resulting in many rearing fish using purely locally soured foods. Understanding the processes involved in maintaining gastrointestinal microbiota is vital because the composition of the microbial community significantly influences a host's growth and survival. This study used 16S rRNA gene sequencing and stable isotope analysis (SIA) to determine how a locally sourced diet affects the gastrointestinal microbiota and nutrient assimilation patterns of GIFT in Papua New Guinea.

A core microbiome consisting of three zOTUs (Fusobacteriaceae) accounted for an average of 52% of the relative bacterial abundance. Despite these similarities, GIFT fed commercial feed pellets were larger than those farmed using local foods. Diet was also found to significantly affect the microbial composition and heterogeneity of GIFT (Figure 1). SIA showed that carbon did not vary significantly between the treatments, however nitrogen was significantly enriched in fish fed a locally sourced diet (Figure 2). Understanding how locally sourced feeds affect the production of GIFT is an important step towards improving feeding practices, particularly
for farmers with low financial capital.