ScholarWorks@경상국립대학교

초록

his 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.

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