Enhanced biodiversity of gut flora and feed efficiency in pond cultured tilapia under reduced frequency feeding strategies

identified microbes varied between treatments with an increase in the proportion of Fusobac- teria (62.6% to 84.6%) and a decline in the proportion of Firmicutes (32.1% to 11.5%) with reductions in feeding frequency from daily to every 3rd day (T1-T3). The fish fed a commer- cial diet only with no fertilization (T5) had the highest proportion of Fusobacteria (90.8%) and lowest proportion of Firmicutes (6.5%) among the treatments. There were 10 unique bacterial OTUs identified in T1, 6 in T2, 1 in T3, 19 in T4, and 4 in T5 (Fig 4, S5 Table). Alpha diversity and rarefaction curves were determined for all treatments evaluated. T1 and T2 had the highest Chao 1 diversity index among the groups (P < 0.05; Chao1 index mean ± SEM; T1, 392.9 ± 108.5 and T2, 371.8 ± 81.0). The bacterial diversity in the fecal mate- rial in tilapia guts declined as the frequency of feeding was reduced to every 3rd day (T3) or where no supplemental feeds were applied (T4) when paired with pond fertilization (Fig 5a, S1a Fig). Although there was no significant difference in species richness due to sample varia- tion within treatments (P = 0.256), treatments with greater access or variety of foodstuff (feed and fertilization) had higher diversity measures. The Chao 1 index was highest for T1 and T2. T3 (187.3 ± 77.6), T4 (244.0 ± 44.2), and T5 (215.5 ± 66.4) had similar diversity indices. Our Fig 2. Gene expression of nutrient transporters in the intestine of Nile tilapia subjected to reduced-feeding

regimes (mean ± SEM). (a) SLC2A5; (b) SLC2A6; (c) SLC27A4; (d) SLC38A2; (e) SLC38A4; (f) SLC43A1. All values reflect copy number / ng Total RNA normalized to 18S rRNA levels. Treatments with different letters are significantly different (P < 0.05). https://doi.org/10.1371/journal.pone.0236100.g002 PLOS ONE Enhanced biodiversity of gut flora and feed efficiency in pond cultured tilapia PLOS ONE | https://doi.org/10.1371/journal.pone.0236100 July 23, 2020 10 / 23