This study was conducted to investigate changes in immunoglobulin G (IgG) concentration, nutrient content, and microbial communities of fresh and heat-treated Holstein colostrum collected from a colostrum bank operated by a local agricultural technology center in Gyeongsangbuk-do, South Korea. Of the 16 colostrum samples, 8 were heated at 60℃ for 30 min under a pressure of 0.9–1 bar. The colostrum samples were stored at −70℃ until use, at which time they were thawed at 50–55℃ in a water bath to analyze IgG levels, chemical composition, and microbiome, which was identified by 16S rRNA gene sequencing using the Illumina MiSeq-PE250 platform. The IgG concentrations were similar in fresh and heat-treated colostrum. The fat, protein, and lactose contents also did not differ in these samples. However, somatic cell count (SCC) was lower in heat-treated colostrum than those in fresh colostrum (p<0.05). At the phylum level for the microbiome of fresh colostrum, Proteobacteria (44.16%) was the most abundant taxa, followed by Bacteroidota (33.26%), Firmicutes (10.04%), Actinobacteriota (7.14%), and a marginal difference in the order of abundance was observed in heat-treated colostrum. At the genus level, bacteria belonging to Sphingomonas, Delftia, Ochrobactrum, Simplicispira, and Lactobacillus were more abundant (p<0.05) in the heat-treated colostrum, while the abundance of Acinetobacter in the fresh colostrum was four times more (p<0.05) than that in the heat-treated colostrum. Our results demonstrated that heating does not affect IgG level and colostrum composition but reduces SCC (p<0.05), suggesting that heat-treated colostrum can potentially be put to further use (e.g., feeding Hanwoo calves) without compromising its quality. Differences in the microbiome between the fresh and heat-treated colostrum were limited. Further studies are required to extensively investigate the quality and safety of colostrum collected from dairy farms to ensure better utilization and processing at a local agricultural technology center.

ABSTRACT
Ⅰ. INTRODUCTION
Ⅱ. MATERIALS AND METHODS
    1. Colostrum preparation
    2. IgG concentration
    3. Colostrum composition
    4. Microbiome analysis of colostrum
    5. Statistical analysis
Ⅲ. RESULTS AND DISCUSSION
    1. IgG concentrations in colostrum
    2. Nutritive value of colostrum
    3. Microbiome of colostrum
Ⅳ. CONCLUSIONS
Ⅴ. ACKNOWLEDGMENTS
Ⅵ. REFERENCES

• Gyeongjin Kim(Department of Animal Science and Biotechnology, Kyungpook National University, Sangju, 37224, Korea)
• Chang Seok Park(Yecheon Agricultural Technology Center, Yecheon, 36819, Korea)
• Minjung Yoon(Department of Animal Science and Biotechnology, Kyungpook National University, Sangju, 37224, Korea, Research Institute for Innovative Animal Science, Kyungpook National University, Sangju, 37224, Korea)
• Junyoung Kim(Department of Animal Science and Biotechnology, Kyungpook National University, Sangju, 37224, Korea)
• Minseok Kim(Division of Animal Science, College of Agriculture and Life Sciences, Chonnam National University, Gwangju, 61186, Korea)
• Seunghyun Mun(Division of Animal Science, College of Agriculture and Life Sciences, Chonnam National University, Gwangju, 61186, Korea)
• Yong Bum Cho(Department of Animal Resource Science, Sahmyook University, Seoul, 01795, Korea)
• Miyoung Won(Subtropical Livestock Research Institute, National Institute of Animal Science, Rural Development Administration, Jeju, 63242, Korea)
• Eun Joong Kim(Department of Animal Science and Biotechnology, Kyungpook National University, Sangju, 37224, Korea, Research Institute for Innovative Animal Science, Kyungpook National University, Sangju, 37224, Korea) Corresponding author