This study evaluated the effects of dietary cellulose-to-starch ratios on nutrient digestibility, fermentation characteristics, and greenhouse gas emissions in the rumen. For 48 h of in vitro rumen incubation, each substrate (0.3 g) was incubated with rumen fluid mixture (30 mL) in quadruplicate. Six treatments were formulated with different ratios of structural (cellulose-based) and non-structural (starch-based) carbohydrates (10:0, 8:2, 6:4, 4:6, 2:8, and 0:10). After incubation, total gas emission was measured and analyzed for CO2 and CH4. The remaining contents were centrifuged to determine rumen fermentation characteristics and digestibility. The crude protein level of all treatments was maintained at 15% by combining soybean meal and urea. After incubation, in vitro dry matter digestibility (IVDMD) and organic matter digestibility (IVOMD) increased linearly with higher starch content, while ammonia-N and total volatile fatty acid (VFA) concentrations decreased quadratically. In addition, acetate concentration and the acetate to propionate (A:P) ratio increased along with starch content (p<0.05), whereas propionate concentration decreased (p<0.05). As starch content increased, CO2 and CH4 emissions based on DM increased linearly (p<0.05) but decreased (p<0.05) quadratically and linearly based on DMD and OMD, respectively. Therefore, this study concluded that the dietary cellulose-to-starch ratios affected rumen fermentation characteristics and greenhouse gas emissions, particularly methane mitigation by increasing dietary starch content. Further study should be conducted to determine the concentrate-to-forage ratio that reduces greenhouse gas emissions without adverse effects on animal performance.

ABSTRACT
Ⅰ. 서론
Ⅱ. 재료 및 방법
    1. 기질 사료
    2. 영양소 함량, 반추위 내 소화율 및 발효특성
    3. 반추위 내 가스 발생량
    4. 통계처리
Ⅲ. 결과 및 고찰
    1. 반추위 내 소화율 및 발효특성
    2. 반추위 내 온실가스 발생량
Ⅳ. 요약
Ⅴ. 사사
Ⅵ. REFERENCES

• 김지윤(경상국립대학교 응용생명과학부(BK21 Four)) | Ji Yoon Kim (Division of Applied Life Science (BK21 Four), Gyeongsang National University, Jinju 52828, Republic of Korea)
• 백창현(경상국립대학교 응용생명과학부(BK21 Four)) | Chang Hyun Baeg (Division of Applied Life Science (BK21 Four), Gyeongsang National University, Jinju 52828, Republic of Korea)
• 최부길(경상국립대학교 응용생명과학부(BK21 Four)) | Bu Gil Choi (Division of Applied Life Science (BK21 Four), Gyeongsang National University, Jinju 52828, Republic of Korea)
• 애린다(경상국립대학교 응용생명과학부(BK21 Four)) | Arrynda Rachma Dyasti Wardani (Division of Applied Life Science (BK21 Four), Gyeongsang National University, Jinju 52828, Republic of Korea)
• 김삼철(경상국립대학교 응용생명과학부(BK21 Four), 경상국립대학교 축산과학부(농업생명과학연구원)) | Sam Churl Kim (Division of Applied Life Science (BK21 Four), Gyeongsang National University, Jinju 52828, Republic of Korea, Division of Animal Science (Institute of Agriculture and Life Science), Gyeongsang National University, Jinju 52828, Republic of Korea) Corresponding author
• 정승민(국립축산과학원 조사료생산시스템과) | Seung Min Jeong (Forages Production Systems Division, National Institute of Animal Science, RDA, Cheonan 31000, Republic of Korea)
• 주영호(경상북도 축산기술연구소) | Young Ho Joo (Gyeongsangbuk-do Livestock Research Institute, Yeongju 36052, Republic of Korea)
• 허태웅(경상국립대학교 축산과학부(농업생명과학연구원)) | Tae Woong Hur (Division of Animal Science (Institute of Agriculture and Life Science), Gyeongsang National University, Jinju 52828, Republic of Korea)