In Korea, the agricultural industry has witnessed a growing emphasis on reducing reliance on imported forage by adopting locally available alternatives to enhance sustainability and self-sufficiency. Given the limited information on the potential use of whole-crop rice silage (WCRS) as livestock feed, this study evaluated the effects of total mixed rations (TMR) containing WCRS on the rumen microbiota of Hanwoo heifers. Thirty heifers (body weight = 351 ± 39 kg) were randomly assigned to three TMR diet groups for the early fattening period: oat hay (OH), oat hay with Italian ryegrass silage and corn silage (OIC), and silages from whole-crop rice, Italian ryegrass, and corn (WCRSEF). During the late fattening period, the same heifers (569 ± 40 kg) were reassigned to three other treatment groups: perennial ryegrass (PRG), Italian ryegrass silage and alfalfa hay (IRGA), and silage containing whole-crop rice (WCRSLF). The effects of different feeding diets on the rumen microbial composition of Hanwoo heifers were investigated using high-throughput 16S rRNA gene sequencing. The analysis revealed similar microbial diversity among the treatments across both fattening periods. Bacteroidetes and Firmicutes were the most dominant phyla during early and late fattening periods. Moreover, during the early fattening period, heifers fed WCRS exhibited a higher ratio of Bacteroidetes to Firmicutes, whereas Firmicutes became more predominant in the late fattening period. Hungateiclostridium and Porphyromonas were identified as biomarkers (LDA score > | 2 |; p < 0.05) for the WCRSEF and WCRSLF groups, respectively. Furthermore, the microbial co-occurrence network highlighted different patterns (| r | = 0.85; p < 0.05) between the early and late fattening periods. The results provide significant insights into the effects of WCRS as a substitute for conventional forages such as oat hay, perennial ryegrass, alfalfa, and Italian ryegrass silage. The findings suggest that WCRS can modulate the rumen microbiome of Hanwoo heifers.

Abstract
Introduction
Materials and Methods
    1. Preparation of total mixed rations
    2. Animals and treatments during the fattening stage
    3. Microbial Community Analysis Using 16S rRNAAmplicon Sequencing
    4. Statistical analyses
Results and Discussion
    1. Ruminal microbial composition and diversity
    2. Network analysis of microbial community
Acknowledgments
References

• Min Jung Ku(Agricultural Researcher, Livestock Research Institute, Jeonnam Agricultural Research and Extension Services, Gangjin 59213, Korea)
• Michelle A. Miguel(Senior Researcher, Department of Animal Science and Technology, Sunchon National University, Suncheon 57922, Korea)
• Chang Dae Jeong(Research Director, Research & Development Center, LJ Bio Co., Ltd., Suncheon 57922, Korea)
• Seon Ho Kim(Research Professor, Department of Animal Science and Technology, Sunchon National University, Suncheon 57922, Korea)
• A Rang Son(Research Professor, Department of Animal Science and Technology, Sunchon National University, Suncheon 57922, Korea)
• Young Sun Choi(Agricultural Researcher, Livestock Research Institute, Jeonnam Agricultural Research and Extension Services, Gangjin 59213, Korea)
• Sang Suk Lee(Professor, Department of Animal Science and Technology, Sunchon National University, Suncheon 57922, Korea) Corresponding author