Department of Animal Sciences, The Ohio State University, Columbus, OH 43210, USA.
J Dairy Sci. 2011 Jan;94(1):396-409. doi: 10.3168/jds.2010-3580.
Variation in milk fat percentage resulting from monensin supplementation to lactating dairy cows could be due to altered ruminal fermentation with interactions of monensin with ruminal biohydrogenation of fat and ruminal carbohydrate availability. The objective of the study was to determine the effects of feeding monensin as Rumensin (R) in diets differing in starch availability (ground or steam-flaked corn), effective fiber (long or short alfalfa hay, LAH or SAH), and 4% fat (F) from distillers grains, roasted soybeans, and an animal-vegetable blend on ruminal fermentation characteristics and milk production in lactating dairy cows. Six ruminally cannulated lactating Holstein cows were used in a balanced 6×6 Latin square design with 21-d periods. The cows were fed 6 diets: (1) C=control diet with ground corn and LAH, (2) CR=C plus R, (3) CRFL=CR plus F, (4) CRFS=ground corn, R, F, and SAH, (5) SRFL=steam-flaked corn, R, F, and LAH, and (6) SRFS=steam-flaked corn, R, F, and SAH. Mean particle size of LAH was 5.00 mm and 1.36 mm for SAH. All diets were formulated to have 21% forage NDF and 40% NFC. The R tended to decrease DMI, decreased milk fat yield, and numerically lowered milk fat percentage (3.41 vs. 2.98%). Addition of F to R diets did not affect milk fat percentage. By feeding diets containing R and F, SAH tended to increase milk fat percentage for the ground-corn diet, but SAH tended to decrease milk fat percentage with steam-flaked corn (CRFL+SRFS vs. CRFS+SRFL). The steam-flaked corn increased total-tract NDF digestibility (CRFL + CRFS vs. SRFL+SRFS; 51.1 vs. 56%). Addition of F with R decreased total VFA concentration and increased rumen pH. Fat addition with R decreased rumen NH3N and MUN (12.8 vs. 13.9 mg/dL), and SFC decreased NH3N concentration compared with ground corn. Although R caused milk fat depression, addition of F did not further exacerbate milk fat depression. Fatty acid analysis did not implicate any particular biohydrogenation intermediate as the causative factor for the milk fat depression.
由于莫能菌素（monensin）对泌乳奶牛瘤胃发酵的影响，牛奶脂肪百分比会发生变化，这可能与莫能菌素与脂肪的瘤胃生物氢化以及瘤胃碳水化合物供应的相互作用有关。本研究的目的是确定在不同淀粉供应（粉碎或蒸汽压片玉米）、有效纤维（长或短苜蓿干草，LAH 或 SAH）和 4%脂肪（来自蒸馏酒糟、烤大豆和动物-植物混合物）的日粮中添加瘤胃能菌素（Rumensin，R）对泌乳奶牛瘤胃发酵特性和产奶量的影响。6 头泌乳荷斯坦奶牛通过平衡 6×6 拉丁方设计进行了瘤胃套管，每个周期 21 天。奶牛饲喂 6 种日粮：（1）C=对照日粮，含粉碎玉米和 LAH；（2）CR=C 加 R；（3）CRFL=CR 加 F；（4）CRFS=含粉碎玉米、R、F 和 SAH；（5）SRFL=蒸汽压片玉米、R、F 和 LAH；（6）SRFS=蒸汽压片玉米、R、F 和 SAH。LAH 的平均粒径为 5.00mm，SAH 为 1.36mm。所有日粮的饲粮纤维中性洗涤纤维（NDF）含量均为 21%，非纤维碳水化合物（NFC）含量为 40%。R 趋于降低干物质采食量（DMI），降低乳脂产量，并且乳脂百分比呈数值降低趋势（3.41%比 2.98%）。在 R 日粮中添加 F 并不影响乳脂百分比。通过饲喂含 R 和 F 的日粮，对于粉碎玉米日粮，SAH 趋于增加乳脂百分比，但对于蒸汽压片玉米，SAH 趋于降低乳脂百分比（CRFL+SRFS 比 CRFS+SRFL）。蒸汽压片玉米增加了全肠道 NDF 消化率（CRFL+CRFS 比 SRFL+SRFS；51.1%比 56%）。R 与 F 一起添加降低了总挥发性脂肪酸浓度并增加了瘤胃 pH 值。R 与 F 一起添加降低了瘤胃氨氮（NH3N）和微生物氮（MUN；12.8 比 13.9mg/dL）和牛奶非纤维碳水化合物（SFC）浓度，与粉碎玉米相比，SFC 降低了 NH3N 浓度。尽管 R 导致乳脂下降，但添加 F 并没有进一步加剧乳脂下降。脂肪酸分析没有表明任何特定的生物氢化中间产物是导致乳脂下降的原因。
