Abstract
This study investigated the effects of ensiled mulberry leaves (EML) and sun-dried mulberry fruit pomace (SMFP) on the ruminal bacterial and archaeal community composition of finishing steers. Corn grain- and cotton meal-based concentrate was partially replaced with EML or SMFP. The diets had similar crude protein (CP), neutral detergent fiber (NDF), and metabolizable energy. Following the feeding trial, the steers were slaughtered and ruminal liquid samples were collected to study the ruminal microbiome. Extraction of DNA, amplification of the V4 region of the 16S rRNA gene, and Illumina MiSeq pyrosequencing were performed for each sample. Following sequence de-noising, chimera checking, and quality trimming, an average of 209,610 sequences were generated per sample. Quantitative real-time PCR was performed to examine the selected bacterial species in the rumen. Our results showed that the predominant phyla were Bacteroidetes (43.90%), Firmicutes (39.06%), Proteobacteria (4.31%), and Tenericutes (2.04%), and the predominant genera included Prevotella (13.82%), Ruminococcus (2.51%), Butyrivibrio (2.38%), and Succiniclasticum (2.26%). Compared to the control group, EML and SMFP groups had a higher abundance of total bacteria (p < 0.001); however, the bacterial community composition was similar among the three groups. At the phylum level, there were no significant differences in Firmicutes (p = 0.7932), Bacteroidetes (p = 0.2330), Tenericutes (p = 0.2811), or Proteobacteria (p = 0.0680) levels among the three groups; however, Fibrobacteres decreased in EML (p = 0.0431). At the genus level, there were no differences in Prevotella (p = 0.4280), Ruminococcus (p = 0.2639), Butyrivibrio (p = 0.4433), or Succiniclasticum (p = 0.0431) levels among the groups. Additionally, the dietary treatments had no significant effects on the archaeal community composition in the rumen. Therefore, EML and SMFP supplementation had no significant effects on the ruminal bacterial or archaeal community composition of finishing steers.
Highlights
Mulberry (Morus spp., family Moraceae), a fast-growing deciduous tree, thrives under variable climatic conditions ranging from temperate to tropical
Our results revealed that the sun-dried mulberry fruit pomace (SMFP)-fed group had lower ruminal ammonia and total volatile fatty acid (VFA) concentrations than the ensiled mulberry leaves (EML)-fed group [10], probably due to differences in the ruminal microbiome between the two groups
EML and SMFP groups had a higher abundance of total bacteria than the control group (CON) group (p < 0.001)
Summary
Mulberry (Morus spp., family Moraceae), a fast-growing deciduous tree, thrives under variable climatic conditions ranging from temperate to tropical. Mulberry leaves are succulent, characterized by high crude protein (CP; 19.4%) and low neutral detergent fiber (NDF; 36.1%) [2]; mulberry fruit pomace is rich in carbohydrates (20.85%), CP (21.86%) and low in NDF (49.06%) [3]. These mulberry by-products represent potential feed sources for herbivores and monogastric animals. Our previous study has shown that ensiled mulberry leaves (EML) and sun-dried mulberry fruit pomace (SMFP) can be used in finishing steer diets without impairing their productive performance or carcass characteristics. Dietary changes affect the ruminal microbiome (i.e., bacteria, protozoa, and fungi) [11,12,13], and changes in the ruminal microbiome affect the digestive capacity of the animal (e.g., improved fiber utilization and/or decreased methane production) [14,15,16]
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