|摘要: ||反芻動物瘤胃經醱酵生成之甲烷，為影響氣候變遷之溫室氣體之一，佔總能攝取量之5~10%。目前降低反芻動物甲烷排放之兩大策略為提升動物生產效率及調整飼糧組成分，例如，改善飼糧中芻料種類、品質及加工方式等。本研究目的為餵飼國內常用芻料對臺灣之荷蘭牛生長性狀、營養分利用率及甲烷排放量之影響。試驗一，建立兩座獨立簡易開放式呼吸室，每室長寬高為550 × 228 × 211 cm3（體積27.7 m3），每室每次置入一頭牛以測定其甲烷排放量，於呼吸室兩側設有2個進氣口（ϕ 30 cm）及1個出氣口（ϕ 30 cm），並在室內靠近出氣口側裝置排風管，藉由排風機抽氣以導引氣體流動，出風口氣體平均流速為15.3 m3/分。試驗用3種芻料為百慕達乾草、燕麥乾草及玉米青貯料，分別佔總飼糧50%，並佐以精料50%。試驗二，依逢機完全區集設計（Randomized Complete Block Design，RCBD）。選用3頭平均體重為526 ± 69公斤，日產乳量為16.3 ± 4.4公斤之初產泌乳牛，依據試驗設計將每頭牛視為一區集，將之依每3週為一期分為3個期別，每一期別視為一個試驗單位，將3種芻料飼糧處理組逢機分配於每頭牛之3個試驗期中。試驗三、選用2頭生長女牛及1頭乾乳牛，將3種芻料飼糧處理組依3 × 3拉丁方格設計（Latin Square Design）分配於該3頭試驗牛。每一試驗期包含14天適應期與7天收集期。於收集期收集飼料、糞便、尿液及瘤胃液等樣品，且以簡易開放式呼吸室測定牛隻甲烷排放量。結果顯示，芻料種類對泌乳牛之生長性狀、乳產量、乳脂校正乳（3.5% FCM）、體內氮及能量平衡、瘤胃pH值與瘤胃液中揮發性脂肪酸濃度等皆無顯著影響，餵飼玉米青貯料之泌乳牛其乾物質、有機質、中洗纖維及半纖維素消化率顯著較低；餵飼燕麥乾草之泌乳牛有顯著較低之甲烷生成量（g/d and kg/yaer）及甲烷能量轉換係數（% of GEI）。芻料種類對非泌乳牛之生長性狀、營養分消耗量、營養分消化率、體內氮及能量平衡與甲烷生成總量等皆無顯著影響。餵飼燕麥乾草之非泌乳牛以甲烷形式釋出之能量顯著較低。綜合上述結果，在不影響生長及泌乳性狀之前提下，為降低荷蘭牛之甲烷生成量，以餵飼燕麥乾草為芻料來源之飼糧應是較適當之選擇。|
Emission of methane is a major concern for ruminant production because of its adverse consequences to climate change. Improved animal productivity and dietary manipulation are two strategies that have shown potential for reducing methane emissions. Factors such as the forage species and quality and processing of forage may influence CH4 production in the rumen. The purpose of this study was to determine methane production as well as growth performance and nutrient utilization of Holstein cows fed with different forages in Taiwan. In experiment 1, two identical brief open-circuit chambers, each with dimension of 5.5 m width � 2.3 m depth � 2.1 m height (volume=27.7 m3), were established. The chambers were equipped with two air inlets (ϕ 30 cm) and an outlet (ϕ 30 cm) with an averaging air flow rate 15.3 m3/min forced by an electric fan. Inlet and outlet gases were sampled every 0.5 hour for CH4 concentration analysis when the cows stayed individually in the chamber. In experiment 2 and 3, three forages, i.e., bermuda hay (BH), oat hay (OH) and corn silage (CS) along with 50% concentrate on DM basis were used as dietary treatments. In experiment 2, three Holstein cows (BW = 526 � 69 kg, DIM = 238 � 143 days) were used and each was regarded as a block that was divided into three 3-week periods, each with 14 d for adaptation and 7 d for collecting samples regarded as an experimental unit. According to a randomized complete block design (RCBD), the treatments were randomly allotted into three periods in a cow. Experiment 3 was conducted with three Holsteins non-lactating cows (BW = 452 � 141 kg) according to a 3 � 3 Latin square design, in which each interval lasting for 21 d including 14 d for adaptation and 7 d for measurements and sample collection. The samples including feces, urine, and rumen fluid were collected and CH4 emission from the cow was determined at each period. The results showed that growth performance, milk production, 3.5% FCM as well as pH value and VFA concentration in the rumen of lactating cows were not significantly different among the forage treatments. CH4 emissions (g/d and kg/year) and CH4 conversion rate (% of gross energy intake) were significant lower by feeding the lactating cows with OH diet. Intake, apparent digestibilities of nutrients as well as retention of nitrogen and energy in the non-lactating cows were not significantly different among the forage treatments. Comparing with the other forages, feeding OH diet to non-lactating cows resulted in the lowest CH4 production and CH4 conversion rate. In conclusion, when decreasing CH4 emission is concerned, oat hay is a proper choice for feeding Holstein cows in Taiwan.