Effects of Rhodopseudomonas palustris on the Rumen Microbiota of Leizhou Goats

This study investigated the effects of <i>Rhodopseudomonas palustris</i> (<i>R. palustris</i>) supplementation on the rumen microbiota of Leizhou goats and explored its potential mechanisms. Thirty healthy Leizhou goats of similar weight and age were selected and randomly assigned to five groups (six goats per group) using a completely randomized block design for a 75-day feeding trial. The control group (CONRF) was fed a basal diet, and the Photosynthetic Bacteria Medium (PBMRF) group was fed a basal diet + PBM solution. The low-concentration <i>R. palustris</i> (LRPRF), medium-concentration <i>R. palustris</i> (MRPRF), and high-concentration <i>R. palustris</i> (HRPRF) groups were fed a base diet supplemented with 20.0 mL, 40.0 mL, and 80.0 mL of <i>R. palustris</i> solution, respectively. All supplements were administered by mixing them into the feed. On day 75 of the trial, three goats were randomly selected from each group for slaughter and evisceration. Rumen contents were collected, immediately filtered, aliquoted, quick-frozen in liquid nitrogen, and stored at -80 °C for subsequent analysis of rumen microbial diversity. Rumen microbial community structure was analyzed using high-throughput sequencing. The results showed that <i>R. palustris</i> enriched unique operational taxonomic units (OTUs), particularly in the LRPRF group. At the phylum level, Firmicutes and Bacteroidota were dominant; Firmicutes and Euryarchaeota abundance increased, while Bacteroidota decreased in the experimental groups. In addition, Verrucomicrobiota abundance was significantly elevated (<i>p</i> < 0.05). At the genus level, Prevotella was predominant, whereas <i>Selenomonas</i> abundance was significantly reduced (<i>p</i> < 0.01). Meanwhile, compared to the CONRF, PBMRF, and LRPRF groups, the MRPRF and HRPRF groups exhibited higher relative abundances of <i>Christensenellaceae_R-7 group</i> and <i>Anaeroplasma</i>. LEfSe analysis revealed a greater number of differential taxa in the experimental groups compared with the control, including enrichment of beneficial bacteria, such as <i>Lactobacillus</i>, which may contribute to optimizing the rumen environment by regulating immune and metabolic functions. Functional prediction indicated that rumen microorganisms were mainly involved in carbohydrate and amino acid metabolism. In conclusion, supplementation with <i>R. palustris</i> can beneficially modulate rumen microbial composition and function and promote rumen absorption of nutrients and degradation of crude fiber. This study provides a theoretical basis for green goat farming practices.