Abstract
Prebiotics that stimulate beneficial microbes have had varying success in improving animal health and enhancing production efficiency. Aspergillus oryzae prebiotics (AOP) are produced from a multi-step fermentation process of a selected strain that have been shown to have beneficial effects on rumen fermentation. However, their effect on the rumen microbiome has not been fully evaluated using up-to-date molecular techniques. The objectives of this study were to assess the effects AOP on rumen fermentation and on bacterial and fungal communities in hope of generating insight into the mechanisms whereby AOP modulates rumen metabolism. The experiment was conducted using an artificial rumen (Rusitec) for 19 d in a completely randomized experiment. Three treatments consisting of the basal diet as Control (C), basal diet supplemented with AOP at 6 mg (AOPl) or 10 mg/fermenter (AOPh) per day were assessed with 4 replicate fermenters per treatment. Total gas production, methane, ammonia, volatile fatty acids (VFA) and microbial protein production were measured. Specific rumen bacteria and methanogens were analyzed using real-time PCR and bacterial (16SrRNA) and fungal (ITS) microbiomes were determined using Illumina MiSeq sequencing technology. Fermentation data were subjected to analysis of variance using the MIXED procedure of SAS with treatment as the main effect, and differences (P < 0.05) among treatments were tested using the LSMEANS procedure of SAS with the PDIFF option. Supplementation of AOP at 6 and 10 mg/fermenter per day linearly increased total gas production (P=0.005), dry matter disappearance (P=0.023), neutral detergent fiber disappearance (P< 0.001), total VFA (P=0.009) and total microbial protein production (P=0.044) with most differences being observed between C and AOPh. However, starch disappearance, methane production and ratio of acetate and propionate were not affected by either AOPl or AOPh. PCR analysis revealed that AOP linearly increased total daily output of 16S rRNA gene copies of total cellulolytic bacteria (sum of Fibrobacter succinogenes, Ruminococcus albus and Ruminococcus flavefaciens; P=0.049) associated with feed particles, with this response being greatest for F. succinogenes (P=0.027). However, treatment had no effect on daily total outputs of the mcrA gene associated with methanogens or on 16S rRNA gene copies of Ruminobacter amylophilus and Selenomonas ruminantium. Microbiome analysis revealed that AOP did not affect diversity and abundances of either bacterial or fungi at the phylum level. However, AOP altered the composition of bacterial and fungal community at the genera level, with and noteworthy increase (P< 0.05) in cellulolytic bacterial and fungal microbiota. These results demonstrated that addition of AOP to an artificial rumen improved fermentation efficiency via positively altering the bacterial and fungal microbiomes involved in fiber digestion.